ALL of CIE IGCSE Biology! | The ONLY revision video you need! | 2025 onwards | 0970 / 0610

welcome to my all-in-one cie igcc biology video I'm so excited that I've made this video cie is something that I've been determined to work on recently and now I finally have time so I really hope you guys find it helpful so yes cie people only now as always my perfect answers pop up throughout the video and they will be the wording that I think you should be including your answers in the exam to score maximum marks now if you want me to do all the hard work for you remember I have perfect answer revision guides available on my website so go check that out and there's also details about any revision courses I might be running however enough about that let's get started we're going to start by looking at features that all living organisms have in common and lots of people call that Mrs nerg or Mrs Gren so remember if they say give some features that all living organisms share you're going to say movement respiration sensitivity you're going to say nutrition excretion uh reproduction and growth and that just means getting bigger so if it's non-living like a virus you can easily say it does not move it does not respire it does not excrete so just list any of the Mrs nug factors and you will get the marks now classification there are billions of organisms that exist on our planet and naming them has become a bit of a nightmare because the more species we discover the more names they need to be assigned and the whole thing gets into a huge mess which is why we need classification systems and this is just a way of classifying organisms into groups based on common features or features that they share now the system we currently use is the binomial naming system and that names all organisms according to two names that is both the spe species and the genus EG myobacterium tuberculosis and that's the bacteria that causes TB we do need to discuss what a species is just to make sure you understand that and this is where groups of organisms can be produced to produce fertile offspring and this is the crucial thing so dogs belong to the same species because they can breed and produce puppies and these puppies should be able to breed with other puppies and produce fertile offspring and so on and so forth remember what happens if a horse and a donkey reproduce well they do reproduce to produce what's called a mule but this does not count as a species because mules are sterile that means that they're infertile so two mules can't breed because they won't produce anything because of the fact that they're sterile so a mule is not a species so the traditional classification system so not Ones based on the binomial method we use now was based on evolutionary similarities and it grouped organisms based on their morphology and Anatomy so effectively leave the bones which made them up a more accurate way of classifying these organisms is to look at greater detail so actually look at their structures and that means looking at the sequence of bases in their DNA and now how these sequence of bases determine which amino acids form which proteins so that's a more accurate way of determining how we should group organisms more similar sequences of DNA so more similar amino acids and proteins are more likely to be closely related right we now need to go over the dichotomous Keys part of the specification now I think the easiest way here is to show you past exam question to work out how you're going to approach it because really I can't just explain it without an example so figure one figure 1.1 shows five different insects um yeah cool those insects are really nicely drawn actually use the key to identify the insects in figure 1.1 and write the letter for each insect in table 1.1 so the easiest way to approach this is from the animal point of view not the table so that is my first recommendation so I'm going to look at insect a first of all you can see it's quite squat it's short and fat it has two antenna poking out the top which are here so make sure you know that those are antenna and it has a striped casing so now let's have a look at how a fits into this table so 1 a body is long and thin that definitely doesn't apply to insect a so I'm going to go to B body is short and rounded yes it is short and rounded so as the table tells me I'm going to go to number three so number 3 a no visible antenna well I can see the antenna I've marked them off so we go to B visible antenna which tells us to go to step four step four body has a striped pattern or body has a dotted pattern I think we can safely say a has a striped pattern which means that a is and excuse my pronunciation graphosoma latum so I'm going to put a in here let's go to B now so B looks like a ladyb actually has very small antenna it has a small round body with spots so one body is long and thin no body is short and rounded yes go to three no visible antenna that's not true we can see it has antenna so B is correct it has visible antenna so we've been told to go to four body has a stripe pattern no and we know that belongs to a anyway body has a dotted pattern yes so B needs to be written here looking at C we've got a fairly rounded body not as round as the first two but fairly we can't see any antenna and it seems to have quite a uniform black color so going in at one body is long and thin no body is short and rounded yes so we're going to go to three three no visible antenna I think we can safely say it has no visible antenna so C goes in here copris lunaris moving on to D so it's long and skinny it has some blobs on it it has antenna so 1 a a body is long and thin yes that's true so we need to go to two 2 a body has a spotted pattern it does have a spotted pattern which is why allais oculatus is D and then never just assume you need to work it out properly and make sure that you agree don't just put e in as that missing Gap so e we can see it's long and thin it's gray it has antenna so we go in at one it body is long and thin yes so we're going to go to two body has a plain pattern I think it's safe to say it is plain which is why I'm going to put e there if we're going to use the correct Nom clature when we're talking about naming things we can talk about the five kingdoms and that consists of plants animals protus bacteria and fungi so what is a vertebrate well it is an animal containing a backbone a vertebrae so your spine is made up a vertebral column so a vertebrate contains a backbone now there are several groups of birs you need to know about and you need to know their distinguishing features so for the mammals their most notable points is that they have furry skin and they have mamory glands which means they produce milk used to feed their offspring moving on to birds they obviously have feathers which you find on their wings and then they have scales on their legs with reptiles so we're talking about lizards and snakes here the most notable thing here is that they have dry scaly skin for fish again lots of scales here they have fins which help them to swim so they have gills where they filter water and remember they have like a flap of skin which covers the gills and we call that the ulum and lastly they have a lateral line containing sense organs for amphibians we're talking about things like frogs they have moist skin I tried to bribe Lyra into sitting on my lap so she's on a cushion princess Lyra has anyone seen that episode of Friends where Rachel brings in the cat without fur on a cushion it's basically Lyra now look what I have to do to convince her to be my friend she likes the cushion so we know what a vertebr is it is an animal no Lyra a she's gone already we know what a v is it is an animal containing a backbone so obviously an invertebrate is something which doesn't have a backbone and now we're going to look at the arthropods which is a group of animals without backbones so they're all invertebrates and they have what's called an exoskeleton which means that their skeleton is found on the outside of their bodies so things like crabs whereas as humans we have endoskeletons because our skeletons are found within our bodies cuz look my bones aren't sticking out unless I've had a horrible horrible accident so starting by looking at the different arthopods we're looking at the myria pods they have antenni which are the things that stick out they have bodies made up of many segments and they have a hard exoskeleton so something like a milipede when you're doing this try and name the different like numbers of wings numbers of legs that sort of thing to help your answer plop out and and state whether they have antenna or not so the insects now well obviously insects have antenna they have bodies made out of three parts which is the thorax which is here and we know this because our lungs are found within the thorax the abdomen is further down and then obviously at the top they have a head they have compound eyes two pairs of wings three pairs of legs so you'll see they have six legs and the last thing to notice which is weird is that they have mouth Parts with arachnid so spiders they have simple eyes they don't have compound eyes they can't see as well as things like flies their head and their thorax are combined we know that spiders have eight legs which means they have four pairs of legs they have powerful jaws because arachnids are predators they kill and eat other animals and they have what's and I love this word they have a spinette which is the place where their spider silk comes out of so the crustacean now lots of people are eating these we're talking about lobsters and crabs for example so what do you think of when you think of a lobster and a crab or you think of their hard outer casing which we actually call a carpes they have claws with serrated edges which is why you don't want to get your finger stuck because that could hurt they obviously have eyes they have jointed Limbs and lastly you may not know this they have gills under their shell we now need to look at plants so starting with flowering plants whose proper name is the angia spms again you just need to list a load of features so first of all they can produce flowers they produce fruits and seeds they have extensive root systems for obtaining water and mineral ions and coupled with this is transport system such as the xylm and florum the stamata allows carbon dioxide into the leaves and oxygen and water out and lastly they can be monoc calans or dians and that's to do with how many leaves they produce initially mono meaning one so a single leaf dellons produce too FRS are extremely different even though they have leaves we have to call the leaves frons and that means that they're long and thin these frons contain sporangia and it's these sporangia that really spores which is how the ferns reproduce they also have what's called underground ryes now this is because they have nodules which are like small blobs which exist underground and what these do is they send out roots and shoots helping our Fern to reproduce they also have very simple root systems so compared with the angiosperms which have extensive root systems we say that ferns have simple true root systems lastly viruses nice and simple here just state that they consist of a protein coat which surrounds genetic materials such as DNA or RNA so we now need to take lots of different types of cell in turn and know quite a lot of information about them so I'm going to start with the bacterial cell we can see from the DI diagram that a bacterial cell has a cell wall sometimes it has a slime capsule around the edge sometimes it has a fella which is a tail that helps the bacteria to move as I've already said it doesn't have a distinct nucleus instead it has a circular chromosome which we call a nucleoid it has other small rings of genetic material we call these plasmids and that remember is important when we talk about genetic engineering then you find more typical things such as cytoplasm and cell membranes in terms of things like whether they're pathogenic or non-pathogenic remember that they can be both so pathogen is a microorganism that causes disease it makes sense therefore that some bacteria are pathogenic such examples include pacus which is responsible for pneumonia tuberculosis remember that's gives people TB where they cough up blood very horrible disease however some bacteria very useful like those used in yogurt making the example here is lactobacillus bulgaricus you remember lastly that bacteria are unicellular which means that they're made of one cell only looking at viruses now because that leads on quite nicely from bacteria these are very very small things they're much smaller than bacteria they're far more simple because they're simply made out of a protein coat which arounds either DNA or RNA they don't have any of the typical organal you would find in other types of cell crucial thing here as I've already said is that they're non-living they do not excrete they do not respire they do not grow they're always pathogenic there's no such thing as a good virus they're always out to hurt you and examples here include the flu virus the cold virus HIV which is very famous because it causes AIDS next up we're looking at the Proto tests this is known as the Dustbin Kingdom lots of of various organisms which don't fit into the other categories fit into protus some of them have animal cell properties some of them have plant cell properties starting with algae and also Corella these both have chloroplast which means they're more plant-like things like amoeba are more animal likee you'll see that they don't have chloroplast they don't have a cell wall as such and they all use diffusion in order to obtain their nutrients and get their oxygen one key one you need to know about is plasmodium this is pathogenic because it causes the disease malaria and the plasmodium is the small protus that lives in the female mosquito's bodies and that's what she injects when she bites you so that's actually what gives you malaria do note that they can either be unicellular or multicellular so made up of one cell or many cells fungi now now fungi they're quite easy because you can draw literally a plant cell but just make it slightly more circular so it has the same organ you would find in a plant cell apart from the fact it obviously doesn't have chloroplast but it does have a cell wall this is made out of chitin you do need to know that has a cell membrane cytoplasm it has a vacuum now there are lots of different examples of fungi including mucco and mushrooms do notice that fungi carry out saprotrophic nutrition and that means that they extracellularly secrete enzymes onto dead matter which it breaks down and then absorbs as its food crucial words here are extracellular secreting enzy which break down dead matter and that's how they actually obtain their food there are some useful examples of fungi including yeast now remember that's used in beer and bread making why because when yeast under goes anerobic respiration that means respiration without oxygen it breaks down glucose into ethanol which is clearly used in beer making and also carbon dioxide and it's those bubbles of carbon dioxide that actually help that bread to rise now we're going to look at the plant and animal cell very basic biology here first of all let's start by the listing the organal that both animal and plant cells share so remember they both have cell membranes cytoplasm nuclei or nucleus they have ribosomes mitochondria now in terms of the plant cell there's a few extra organal you need to list that's the cell wall the vacu and also chloroplasts we now need to look at the role of each of those organ and turns so because it's so key that you get these really basic questions right in your exam because if they say what does the nucleus do you need to be able to write that so what does the nucleus do it controls the activities of the cell what does the cytoplasm do it's where chemical reactions take place what is the role of the cell membrane it controls what enters and leaves the cell what is the role of ribosomes it's where protein synthesis takes place I.E where proteins are made which organisms do not contain mitochondria looking more closely at the plant cell now what is the role of the cell wall first of all state that the cell wool is made out of cellulose and that it protects and supports the cell the vacu remember that's filled with cell sap which also helps to maintain the structure of the cell lastly chloroplast remember they're full of a green pigment called chlorophyll it gives leaves the green color and that's where photosynthesis takes place a couple of tricky words you may have come across is UK carots and procaryotes don't worry it's just a very Posh way of describing the type of cell we're talking about ukar are all animal cells as we know it and that's because they contain membrane bound organel such as nuclei mitochondria Etc so an animal cell like I said is an example of a eukariotic cell procariota here because they contain no membrane bound organal so they contain no nuclei which we know because they contain strands of DNA instead so specializ cells this is a nice topic I would get into the habit of drawing out each cell and then labeling it and then hopefully it'll be easier to learn than just a list of separate points so starting with the red blood cell clearly that transports oxygen around the body it does this because it contains a protein pigment called hemoglobin which binds to the oxygen forming oxyhemoglobin in order to improve its efficiency it has a very distinct shape so it is a biconcave dis shape which means it has an increased surface area to volume ratio so it can transport more oxygen and it has no nucleus to allow for more hemoglobin it's also extremely flexible allowing it to pass through the smallest spaces and along the narrowest of capillaries the muscle cell this is adapted so that it can contract and relax in order to move the muscles cells here are very long and contain protein fibers and the protein fibers can shorten when there is energy available which means that the muscle contracts the ciliated cell we find lining the trachea so we're looking at our respiratory system and remember the trachea is actually the windpipe so the cated cell contains Celia these are small hairs which waft and what they do is they waft mucus ladened with bacteria out of the Chia into the mouth where it can be swallowed and destroyed by the hydrochloric acid in the stomach and this is a really good defense system against microorganisms the motor nerve cell remember there are lots of different nerve cells this is the motor so it transports signals from the central nervous system to the affector so its real role is to conduct electrical impulses the long part of that motor cell is called the axon and that carries the electrical impulse don't forget that it is surrounded by a fatty sheath which we call the myin sheath and that increases the speed at which the impulses may be conducted they have lots of branched endings so that they can reach lots of other cells the sperm cell now remember these are made by the testes of males so the whole point of a sperm cell is reproduction remember it fuses with the ovam in fertilization to produce a zygote so its real role is reproduction now it has to swim through the vagina through the cervix through the uterus to the overd duct where fertilization takes place and it has a flagellum a tail to enable this it has a whiplash tail to help it to swim its middle section contains many mitochondria which makes sense because they release lots of energy required to power that sperm on its long journey in its head it contains an acrosome which is full of digestive enzymes which help to digest the outer layer of that egg so it can actually penetrate it and don't forget that its nucleus is hloy which means it contains only one set of chromosomes which makes sense because the ovam also contains only one set of chromosomes so when they fuse at fertilization a diploid cell is made which makes sense because we want our zygote to be deployed because it will then go on and become our baby so the ovam now we've already said it's involved in reproduction we said it contains a hloy number of chromosomes in its nucleus the only thing to notice here that it has a outer layer which is like a jelly coat that changes once the sperm has penetrated through moving on to plants now so the root hair cell has a very distinctive shape why because remember its primary role is to absorb water and mineral ions so it has an root hair which will increase the surface area for absorption and this absorption occurs by osmosis in terms of water and mineral ions are absorbed by active transport I've already touched on the xylm and the flo let's look at them in more detail now so the xylm transports water and it transports the water from the roots up the plant to the leaves to the shoots where it's required now it is made out of dead cells which form a continuous column the end of the cells has broken down so there's no cytoplasm and that means you effectively have a drain pipe to transport that water do notice that its walls are made out of ligin and that helps to strengthen the xylem and stop it collapsing the florum transports sugars when we look at the structure of the leaf and we look at the layers we know that is the palisade layer which is the Palisade misail and these are what your regular plant cells look like so do remember that they just contain lots of chloroplast which absorb sunlight for photosynthesis which means they make sugar or they make glucose for the plant now we're going to look at organization within organisms so we're looking at Key definitions The crucial thing here is to just learn one definition and then just use it as a template for all your other definitions so I'll explain what I'm talking about right now so if we start we look at a cell now remember cells are full of organal which I've just listed nucleus cell membrane Etc so what is a cell well it's a group of organal working together to perform the same function we're going up a step further so we're now looking at tissue what is a tissue it's a group of cells working together to perform the same function then we're going to look at organs so what is an organ it's a group of tissues working together to perform the same function and lastly what is an organ system it's a group of organs working together to perform the same function and lastly what is an organism well it's a group of organ systems working together to perform the same function now I need to list all the various organ systems within the body which I've always been really bad at remembering all of them so I'm going to try there's the digestive system there's the endocrine system reproductive system circulatory system respiratory system nervous system and excretory system but if we focus in on the digestive system for example we could first of all take the fact that the digestive system is obviously the system so what organs make up that digestive system that organ system well it's things like the stomach esophagus pancreas small intestine large intestine then we look can look at the tissues so for example in the stomach you've got glandular tissue which secretes Hydrochloric acid you've got muscular tissue which helps churn the food don't worry too much about this detail by the way I just want you to get the full picture so you're not thrown off if a question slightly strange in the exam and then you can obviously look at the cellular level within the stomach and the organ naels so it's a big hierarchy really so lots of people struggle with converting units and I wanted to give you a really straightforward way of doing this so let's have a look down here we've got lots of different scientifically approved units so we've got the Pico meter which most of you won't come across but I've just added it there for completeness sake then we have the nanometer here which is far more likely to come up micrometer millimeter which you'll be familiar with because you'll have that on your rulers meter which is obviously much larger than that you might have wooden meter long rulers in your science lab but you won't really come across them apart from there kilometers that's very straightforward because we know kilometers how many kilometers is it to the beach five and then lastly Mega meter here which you probably haven't come across so what I'm trying to show you here is you can use this simple expedient of timesing by a th to convert between the various steps so to get from millimeters to micrometers simply Times by thousand to get from micrometers to nanometers Times by a th000 it obviously works the other way around if you need to get from nanometers here to micrometers here divide by a th000 but I didn't want to make this diagram too complicated so as long as you know what you're doing you can obviously reverse it and I'm going to show you some examples right now so let's start by converting 5 m to micromet so let's have a look in our table and we need Times by a th000 twice and then just write out your answer now so it becomes 5 million micromet we're now converting 3 mm to micromet so we're going from here to here so we just need to Times by a th so we're just timesing by 1,000 WS next up converting 10 cm to nanometers this is more complicated because we've got centimeters which isn't included here so let's first of all convert cm to millim hopefully that's really straightforward for you because again you have a ruler it says 10 cm on it and you'll be able to work out from your ruler that 1 cm is 10 mm so therefore 10 cm is going to be a 100 mm and then we're just looking back at our little table thing and we need to see how we're getting from millimet to nanometers and we're timesing by 1,00 twice and let's just add some little commas to try and make that make more sense so that's 100 million nanom and now we're going to go the other way so we're converting 22 m m 2 mm so this time we need to divide by a th so 22 micromet is 0.022 millet so now we're going to practice what we've just learned and we're going to start by looking at question one on the right hand side the diagram below shows the general structure of an animal cell as seen under an electron microscope calculate the magnification of the image and show you're working so let's start by writing our formula triangle out that does not look like a triangle so it's I am which means that magnification equals the image size over the actual size the easiest way to do this is not actually measure the diameter of the cell you need to use this scale bar here we can see from the scale bar that its size is five micrometers so we're going to put that there as the actual size in terms of the image size you're going to use your ruler to measure the length of that line here I know it's hard cuz I'm doing on the iPad but let me tell you that it is 17 mm now the important thing with these calculations is to get all the units being the same so remember I just taught you how to convert so if you actually look back in the video you can see this but to get from millimeters to micrometers remember you times by a th000 so let's convert 17 mm to micrometers by adding 3s / it by 5 and you get a magnific which is 3,400 time as big the photograph shows parts of the cytoplasm of a cell the magnification of this image is 200,000 calculate the actual width of the organal X show you're working so as always using our triangle I am we're looking for the actual length so that's going to be image size over magnification so let's substitute in the magnification first of all cuz that's nice and straightforward you're going to use your ruler now to work out the width it's the width not the length of organal X so do that in millim and you'll get an answer which is 20 mm I like to keep my units in so I know what's going on we're converting that to micrometers as per usual so that becomes 20,000 ID 200,000 giving us a value which is 0.1 micromet now we're moving on to transport so let's first of all touch on the three types of transport so we're looking at diffusion osmosis and active transport so you need to know the definitions of these terms in great amount of detail now remember with diffusion it's the net movement of particles from an area of high concentration to an area of low concentration so that's the reason why you spray perfume in one side of the room where there's a high concentration of perfume particles and it moves across to the other side of the room where you can smell it that is by diffusion it is a passive process it does not require energy osmosis is very similar to diffusion however it involves the movement of water which is why our definition this time is osmosis is the net movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane now potential is just a really Posh way of saying concentration so someone where there's lots of water to somewhere where there's little water and do add that it's across a partially permeable membrane if there's no partially permeable membrane it's not osmosis it's just diffusion so notice when water leaves the stomata from that leaf that is by diffusion CU stas is a whole not a partic the permeable membrane lastly active transport as the name suggests it's an active process this means it requires energy the reason being is because it's the net movement from an area of low concentration to an area of high concentration so against the concentration gradient so we need to go into slightly more detail about how active transport actually works so remember that there are carrier proteins within the membrane these carrier proteins recognize the particle to be transported the particle is transported across the membrane using the Caro protein and this process requires energy from ATP particles then obviously released into the cell and lastly the carry protein returns to its original position let's touch on amoeba now remember LBA is an example of a protus this is a single celled organism which can use diffusion in order to obtain all the nutrients it needs so oxygen diffuses from outside that amoeba into the amoeba from an area of high concentration surrounding the amoeba to a low concentration inside the amoeba the reason why diffusion is appropriate is because because it occurs very quickly because the amra is single CED which means it has a large surface area to volume ratio and therefore the speed of diffusion is fast enough to allow oxygen in as and when it is required larger organisms which are multicellular have a much smaller surface area to volume ratio diffusion is not suitable it is too slow which is why they develop the need for circulatory system so we need to look at biological molecules starting with Organic comp compounds and organic means relating to the element carbon and we're including in our organic compounds carbohydrates lipids and proteins so starting with carbohydrates look at the name to work out which elements exist within it so carbo meaning containing carbon hydrated meaning containing the elements found in water so they contain hydrogen and oxygen also proteins also contain the elements nitrogen and sulfur and nucleic acids contain the elements phosphorus and also sulfur we look at carbohydrates we can divide them broadly into two groups these are monosaccharides and polysaccharides polysaccharides contain many sugars key examples here include cellulose which is the sugar found in cell walls and also starch which remember is the storage compound found within plants and glycogen which is found within animals and fungi so looking at proteins now so what is a protein well it's a chain of amino acids whose order has been determined by genes this sequence of amino acids determines the protein shap shape and the protein shape and structure give the protein its particular function so for example amino acids found within keratin which is a protein give its very structural support function whereas amino acids found in hemoglobin give it a very different role which is to do with the transport of oxygen looking more closely at DNA now so we need to first of all know what the structure of DNA is remember looks like a ladder we call this a double helix which winds itself up it's made up of a sugar phosphate backbone and remember that the sugar here is deoxy ribos why because DNA stands for deoy deoxy ribos nucleic acid so the sugar here is deoxy ribos there's a phosphate and sugar backbone and then linking the two backbones the rungs of the ladder are bases and remember the names of these bases adenine thymine ganine and cytosine looking more in depth the various names involved nucleotide a nucleotide is simply just three units made up of a deoxy VI sugar a phosphate and L A base so it could be either one of those bases I've just mentioned so Adine thyine cytosine or ganine sorry are you is that you I said it gu I got guine really but it sounds weird now he's saying it M's telling me that I'm pronouncing guine wrong my biology teacher said ganine and I don't know how to say it any other way apparently he says guanine H so he's like what an idiot um so we are need to now look at complimentary based pairing that's when the various bases pair up in a very specific way try and remember the shape of the letters match so guanine or guanine always pairs with cytosine because they're both curly in terms of the G and the C adamine and thyine always pair up and that's because they're the straight so use that to help you remember enzymes are key proteins which we need to know lots about that an enzyme is a biological catalyst this means that it speeds up the rate of a chemical reaction without being used up now an enzyme has a very special part on it called an active site and that's the biologically active part of the molecule and what happens is the substrate molecule binds to that active side it forms an enzyme substrate complex which then splits up to form the useful product that we're after now we need to just touch on enzyme activity so the two things you can alter is both the temperature and the pH so if you look at this graph you can see at low temperatures the enzyme activity is low the reason for this is all to do with chemistry it's to do with Collision Theory because at low temperatures enzymes have very little kinetic energy as do the substrate molecules so it means that the enzymes and substrate aren't coming into contact very often that means they obviously can't bind at the active site and so the reaction can't be catalyzed catalyzed catalyzed as we increase the temperature you can see the enzyme activity increases that's because those molecules are coming together more often and at 37° as is the case with most animals you will find the enzyme activity has reached its peak it is at its Optimum temperature the best temperature and that means the enzymes and substrates are coming together very frequently after this temperature and above this temperature we see a massive decrease in in enzyme activity and that's because the enzyme has become denatured never say the word killed they're not living they can't be killed you need to say they're denatured and what that means is that the enzyme active site has changed shape meaning that the substrate can no longer fit if we take a look at pH now you can see a very distinctive graph shape here and that's because enzymes have different Optimum phes and if the pH is either too high or too low around that optimum pH you'll find that the enzyme D Natures which is why you have that cone shape because let's look at the enzyme which has an optimum pH of s if you go to 6.5 or 7.5 the enzyme will denat and this is true for all enzymes some enzymes prefer different phes to other ones so proteases in the stomach for example because they're surrounded by hydrochloric acid they'll have an optimum pH of approximately three whereas throughout the rest of the digestive system you find a slightly alkaline optimum pH so of around eight which is why you can't take stom stomach proteas and put it in this one intestine and expect it to be okay right we're going to be talking about all things to do with plants starting with that key plant process photosynthesis remember photosynthesis is carried out in the chloroplast of plant cells they contain chlorophyll which absorbs that sunlight and actually carries out the process of photosynthesis and this is the method by which green plants make their own food so let's start by looking at the word equation for photosynthesis remember that it's carbon dioxide plus water forms glucose and oxygen this is why it's such a great process because of the huge volume of oxygen photosynthesis releases in terms of the balanced symbol equation try and learn this sof by heart and remember that 6 is very important so you've got 6 CO2 plus 6 H2O forms C6 h126 + 62 now unfortunately there are lots of different factors which can act to reduce or limit the rate of photosynthesis and we call these limiting factors you need to know the definition of a limiting factor it's a factor which in a reaction is in the shortest Supply and a lack of this factor is the reason why rate of reaction no longer increases now in terms of photosynthesis there are three limiting factors you need to know about these are carbon dioxide light intensity and temperature so any one of these may act to limit how much photosynthesis can take place and we're going to talk about each of these in turn in a different situation so let's think about early morning we have a green plant and it's trying to photosynthesize in early morning but what could be limiting how much photosynthesis takes place well it's early morning so it's quite cold so obviously temperature is going to be a limiting factor here another limiting factor will most likely be light intensity because it's not as light early morning as it is at midday day so despite carbon dioxide levels increasing you will find that low light levels low temperatures limit the rate of photosynthesis the reason being is that in the morning low temperatures obviously mean low kinetic energy so all those enzymes involved in those chemical reactions involved in photosynthesis can't actually come together they don't Collide as frequently with their substrate molecules and that's all because of lth or kinetic energy if we take midday now we know that the temperature will have increased ined we know that the light levels will increase so neither of these things will be limiting factors the most likely limiting factor in midday will be Caron Dark Side levels and be sure that you can look at grass on all of these factors and make sure you understand what is going on let's quickly look at the role of diffusion in gas exchange in plants so remember that carbon dioxide is needed by plants in photosynthesis so it will diffuse into the leaf through through the stamata oxygen is released by photosynthesis so that will diffuse out of the leaf also by diffusion however don't forget that plants are living organisms so that they respire which is a bit confusing which means they need some oxygen obviously in order to carry out respiration so if you look at it over the course of the day you will find during the night because the plant can't photosynthesize because obviously there's no light it will just be respiring which means that more oxygen will enter the then will exit the leaf during the day photosynthesis tends to occur at faster rate than respiration so in this case more oxygen will leave the leaf compared with diffusing into the leaf so we know photosynthesis is the method by which plants make food and they make that in the form of glucose so what do they do with that glucose well remember that glucose contains carbon hydrogen oxygen so obviously contains components that can be used to make other biological molecules and this includes fats and proteins so that glucose is used to make fats and proteins it's used to make storage compounds such as starch which the plant can call upon in lean times and it's also used to make the sugar cellulose which is an important component of plant cell walls because it gives it its structural Integrity relating to the plant mineral ions luckily you don't need to know too much just learn the role of nitrates and magnesium so the mineral ions are present in the soil of around the roots of the plant and the plant obviously needs them to be healthy so it absorbs both magnesium and nitrates by active transport so against the concentration gradient and it uses the nitrates to build proteins and it uses the Magnesium to manufacture the chlorophyll found in chloroplast you need to know some deficiency signs so with magnesium clearly you won't be able to manufacture chloroplast or chlorophyll anymore so you see yellow leaves and if you've got a lack of nitrates you will see a stunted poorly grown plant so it's very short carrying on with the plant theme we're now going to look at the structure of a leaf and how it is adapted for photosynthesis let's make some generic comments at the beginning by stating that a leaf has a large surface area which is obvious so that it can absorb more light it's thin so the gases don't have to diffuse too far looking very closely now at the structure of the leaf you need to be able to label all those layers and discuss which each of them do and you need to be very specific here so we're going to start with the waxy cuticle the waxy cuticle is there to prevent transpiration and remember that transpiration is the loss of water from the leaf so a nice thick waxy cuticle prevents excess water loss next up we have the upper epidermis remember this is transparent and it allows light to enter the leaf you don't need to say anything more than that the layer beneath this is the Palisade misail misil is just a FY we same tissue the palis maphil is what your generic plant cell looks like so it's your rectangle Block it's crammed full of chloroplast so it contains lots of chloroplast for photosynthesis and this is where photosynthesis takes place under this you have the spongy misil the important thing to note here is the presence of plenty of air spaces which allow Gases such as carbon dioxide and oxygen to diffuse you'll also find the vein here and the vein contains the and the flum the xylm brings water into the leaf the flum transports sugar away from the leaf then we have the lower idamis not a lot to say here the next layer is the most important layer and that contains the guard cells and the stamata now the guard cells control whether the stamata are open or closed and the stomata allow carbon dioxide into the leaf and oxygen and water to leave the leaf balanced diet so what is a balanced diet well it's one which provides all the nutrients in the correct proportions which are needed to carry out life processes moving on to humans now we're looking at balanced diet so we need to look at the various nutrients that you need for a balanced diet their roles within the body the foods that they're found in and any deficiency diseases so let's have a look and start by listing these nutrients so we're looking at carbohydrates fats proteins minerals vitamins water and fiber I hope I've listed them all so starts with carbohydrates foods which contain lots of carbohydrates include things like bread and rice and pasta carbohydrates are an important source of energy proteins now now you find lots of protein in meat such as chicken and beef protein is important for the growth and repair of muscles now remember lots of people take protein shapes to the gym why because they're trying to build their muscles at the same time so that they like to take a source of protein so try and remember it from that point of view if you have a lack of protein you get a really horrible disease called quoco people are seem very distinctive all like stomach where your stomach comes out super far and that's the symptom of quoco fats foods which contain a lot of fat include dairy foods such as butter and cream I'm just giving you a few examples it's not exhaustive now fats are a very concentrated source of energy and they provide insulation I.E they help to keep you warm moving on to some specific examples of vitamins so vitamin C you find this in citrous fruits such as oranges and lemons vitamin C is important for the repair of tissues so it helps to stick together the cells in the lining of your mouth and if you don't have enough vitamin C you get a disease called scurvy which was um Infamous in the 1500s when sailors used to go out to seea they never got enough oranges and lemons and then you'd see very characteristic mouth bleeds so scurvy is the deficiency disease and the way way to get rid of that is by eating lots of oranges and lemons vitamin D now now vitamin D is important for strong bones you find it in fish liver oils which is gross I hate cold liver oil but it's also manufactured by the action of the sun on the skin so you can get a lot of vitamin D sunbathing but obviously not too much don't get burnt that's not a good idea either and lack of vitamin D leads to rickets in children now we're going to move on to minerals such as iron iron is found in red meat and spinach it's important for healthy blood it's a really important component of hemoglobin which is found in red blood cells lack of iron leads to anemia which is when you feel really tired and exhausted all the time and lastly calcium calcium is a mineral which is important for strong teeth and bones it's found in dairy products such as milk lack of calcium will also lead to rickets last two things fiber so fiber is essential to help food move through your digestive system without fiber you're liable to get constipation vegetables and fruit contain a lot of fiber and water water we know we need to survive without it we would die very quickly and that's because it supports all the chemical reactions that take place in our bodies and just be aware of a deficiency in energy and protein is known as marasmus and that's when you see muscle wasting on limbs now an important side not is to notice that we need a balanced diet full of all these nutrients in order to stay healthy but obviously our requirements will vary depending on our age so older people will need less food less of each of these nutrients compared with teenagers for example pregnant women they'll need more because they're supporting the growing fetus teenage girls will need more iron because they've started their periods people who exercise will need more protein to help them with the growth and repair of their muscles and lastly pregnant women will need more dietary energy compared with people who are not pregnant so it's a bit of a Common Sense part of the specification but just be aware that there are differing requirements now we need to look at digestion let's first of all discuss the definition of digestion which is that it's the breakdown of large insoluble molecules into small soluble ones the reason being that we need to take our food into our mouth and we need to break it down into teeny tiny pieces change its structure so that it can be absorbed through the walls of the small intestine so that's what we're on about when we're talking about digestion so there are various enzymes you need to be aware of firstly amalay and notice the enzymes tend to end in ASE so A's amalay is made in the salivary glands in your small intestine and your pancreas and what amalay does is it catalyzes the breakdown of starch into glucose now we need to look at proteas this is more straightforward because as the name suggests it breaks down proteins so protein is the substrate and it breaks down proteins into amino acids these are the products and proteases found in your stomach in your small intestin and your pancreas slightly more detail on proteas enzymes then so we know these break down proteins however there are two you need to know the name of and that is pepsin and Trin pepsin is simply the proteas found within the stomach whereas Trin is found within the small intestine the last enzyme you need to be aware of is lipase lipase breaks down lipids or fats as they're more Lo your name and lipids are broken down into fatty acids and glycerol so do try and remember that's the most complicated one now I've already told you about chemical digestion which relates to enzymes entirely because that's totally altering the structure of the food molecule we need to also look at mechanical digestion which is a far more physical process that involves just chopping that food up into smaller pieces but doesn't alter the structure of that food so if we you think about where mechanical digestion takes place it will be in the mouth your teeth chew it'll also be in your stomach where your muscular walls turn that food up and break it up into smaller chunks so the teeth right we need to be able to name all the teeth and talk about what they do remember the teeth are very important in mechanical digestion they actually alter the size of the food to make it more easily digestible by enzymes so let's name our various teeth so the front teeth here are known as the incizors their job is simply to to cut or slice food the canines which in humans has become hugely reduced but in animals like dogs you see that they're very long and pointed this grips the food so it holds it in place then you have larger teeth behind that which we call the pre molers their job is to crush and chew the food and then the larger teeth at the back they're the MERS they provide the Grinding Service surface to actually grind that food up so so what causes teeth tooth decay so very painful when we have cavities now that's all to do with the bacteria because obviously the bacteria feed on any excess food in your mouth which is why it's so important that you clean your teeth properly so the bacteria stick to your teeth and they make that plaque which the dentist can sometimes scrape off the bacteria respire and while they're doing this they produce an acid and it's actually that acid which RADS away your teeth so particularly the enamel and the dentine of your teeth so how can we actually protect our teeth well clearly we need to eat diet low sugar because we know sugar speeds up the rate of Decay we need to brush our teeth regularly and ideally after a meal rinse to remove any excess food that might be stuck between your teeth and I've even read that you can eat crunchy vegetables cuz they effectively help remove that food too so we'll start at the mouth so I've already said we've got physical digestion from the teeth chemical digestion comes from Amal which digests starch into glucose the food that then passes down the food pipe which we're going to have to call the esophagus and peristalsis is a process whereby the muscular contractions of the esophagal wall force that bolus that ball of food down into your stomach here muscular contractions of the stomach lining help churn the food you've got the secretion of hydrochloric acid this has two jobs it breaks down the food and also destroys pathogens and that's the reason why you don't get sick all the time if you eat some slightly dodgy food sometimes the Fuji vant is so dodgy that you still get sick but for the most part you'll find your stomach acid will destroy those pathogens remember a pathogen is a microorganism which causes disease proteas is secreted that breaks down proteins into amino acids at this point the stomach empties and the food flows into the small intestine well there'll be further peristaltic contractions I don't know if that's the exact version of the word peristalsis it's similar enough which force the food along we've got more enzymes being added here lipase protease and amalay and note that they'll have a differing optimum pH from the proteas in the stomach they'll have a much higher optimum pH we need to mention bile now now bile is an interesting substance I think it's green it's made in the liver you must remember that it's stored in the ghl bladder and it's released into the small intestine and it has two main Jobs first of all is an emulsifier and what that means is that it breaks up large fat droplets into smaller fat droplets why because it creates much larger surface area because small droplets have a much larger surface area than large droplets and that means that lipas can work more easily on the lipid molecules on the fat molecules but if you can't be bother to write all that just say that it multiplies it second role is to neutralize stomach acid it brings up the pH to an alkaline pH approximately 7 or eight and what that does is it means that those enzymes that have been released into the small intestine don't get denatured by all the acidic food coming along so that's B's two main jobs to emulsify and to neutralize so at this point we've done lots of digesting our food molecules are very small they're very soble which means they can now pass through the walls of the small intestine into the bloodstream they often ask you what the adaptations are of the small intestine lining so you're going to talk about Vine primarily so remember V are these structures shaped like this and they provide a very large surface area for absorption and that's also maximized by the presence of micro this video is so um detailed it's making me lose my voice so yeah micro help increase the surer further you've got a short diffusion distance you've got a plentiful supply of blood capillaries and you've also got the presence of Lacs which are for fat absorption so the small intestine is extremely adapted for for its role going into more detail to do with the microvillus therefore so we know it increases the surface area for absorption the epithelium is one cell thick which provides a short diffusion pathway goblet cells produce mucus like in the trachea and what this does is protects the lining of the small intestine good blood supply from within the micro to transport those digested food stuffs away from the small intestine to elsewhere in the body and lastly the L transports fatty acids and glycerol so once all that food has been absorbed and you've just got the leftover undigestible food it passes into the large intestine and here water is reabsorbed into the blood lastly the feces because we're now at the feces stage that's the fancy word for poo the fees are stored in the rectum before they pass out of your body via the anus we call this egestion the removal of feces from the anus not to be confused with excretion you do not excrete feces you e Gest them excretion has a different definition it is the removal of waste products of metabolism and just to touch on a couple more definitions ingestion is the taking in of food into the body and metabolism is the rate at which chemical reactions take place in the body let's look at transport in plants so we're going to start by looking at two vessels two tissues you need to know lots about that is the zym and the floam make sure you can label these both inside the root at cross-section and inside the stem note that in the root the X matches with the xylm which is why the X in the middle of the root is xylm that's a nice way of remembering whereas the circles around that X are the FL inside the stem it's slightly different the outer layer of tissue is the flum the inner layer is the xylm try and remember this because the flum transports sugar and aphids are little insects which bite into that stem in order to steal some food so they're biting in so that they can reach that flow and they take the food so the FL is on the outside of the stem so looking more closely at the RS as I've already told you FL transports glucose and it transports it from the leaves where it's made in photosynthesis to other parts of the plant so to Growing regions such as flowers in the tops of stems and to storage regions such as the roots and that's where it's stored to starch xylm transports water this time and mineral ions from The Roots where it's absorbed through the root hair cells up the plant to the leaves in various places so this is an important thing for you to note xylm only transports water upwards flow and transports both up and down the Plant in terms of the structures because is transporting water and minerals ions it needs to be very strong and notice that it's made out of dead cells which are stacked on top of each other so there's no organes in there obstructing the flow of water there's also lignin which helps to reinforce those walls further Flo has a different structure just list some keywords here don't talk too much about it it has C plates tubes and it has companion cells and those companion cells contain lots of mitochondria so that they can release energy so that Sugar can be actively transported in and out of the FL we're now going to look at how the mineral ions enter the plant so I think I've already told you this that they enter by active transport they enter against the concentration gradient the reason being is there's far fewer mineral ions in the soil compared with what's inside the plant the plant is greedy it wants as many mineral ions as possible so because it's against the concentration gradient from a low concentration in the soil to the high concentration in the plant it absorbs it using active transport into that root hairell looking at how water is absorbed again through the root hael this is by osmosis so it's from an area of high water potential in the soil to an area of low water potential inside that root hair cell lastly how does water move up through the plant well just to give you a bit of chemistry background here remember that water leaves the leaf at the stomata by transpiration so as the stomata open the first droplet leaves but because water molecules are all attracted to each other due to the presence of hydrogen bonding this forms a continuous column within the xylm so it's a huge chain of water molecules so as one leaves the stomata another one is drawn up from below and we call this transpiration stream you need to know about how the rates of transpiration may be increased and decreased so transpiration let's remind ourselves it's the loss of water vapor from the surface of the leaf I.E through the stamata so we're looking at how that water is leaving the leaf so how might we increase the rate at which that occurs and I always say think about washing drying outside what sort of conditions would you want for your washing to make it dry nice and quickly so first of all we want it to be dry and the same here this increases transpiration rates when it is dry why is this and that's because because there are very few water molecules in the air surrounding the leaf there's far more water inside the leaf therefore water will diffuse out through the stomato very quickly when it is dry if we look at when it's humid so when there's lots of water in the a it feels really yucky on your skin there's a lot of water in the air surrounding the leaf lots of water in the leaf there's not a lot of difference between the water molecules inside and outside of the leaf so diffusion is going to occur very slowly when it is humid next next up what's going to make our washing dry nice and quickly high temperatures we know this in hot countries our beach towels dry nice and quickly same with transpiration increased temperature leads to increased transpiration this is because the water molecules have more kinetic energy and therefore they can simply diffuse faster out of the leaf next up we want wind for our washing and again windiness will increase transpiration rate the reason being that the wind blows those water molecules away from the surface of the leaf effectively increase in the concentration gradient so diffusion will occur nice and quickly and then the last point which has nothing to do with washing drying is Sun so when it is sunnier you will find that there is more transpiration the reason being that because it's sunny the plant wants to photosynthesize a lot so it opens its tomato in order to leten that carbon dioxide which is needed for photosynthesis and clearly because the tomato is now open water can automatically leave so what is the actual purpose of transpiration why is it a good thing because at the end of the day we're just seeing water leaving the plant which seems like a bit of a waste firstly the water flowing in the xylem helps to support the plant it keeps it upright and this is why when the plant doesn't have enough water it starts to wilt it just doesn't have enough water to make its cells tured secondly it cools the plant thirdly it provides a method for delivering mineral ions around the plant and number four IT Supplies water for photosynthesis this let's now look at transport in animals now we're going to talk about the circulatory system so we need to look at the heart I've already talked a little bit about multicellular versus unicellular organisms the reason why organisms such as ourselves humans require circulatory system is because our surface area to volume ratio is too small and diffusion is too slow so we need a circulatory system which actually acts to transport oxygen around our bodies so that's the reason why we have a circulatory system the heart forms the epicenter of our circulatory system it is the pump which delivers oxygen around our bodies and you've got to know detailed information about how this actually happens so we're going to divide the heart into four do remember that we switch over the left and right sides when we're looking at a diagram why because we're picking up the heart and pting it into to our bodies so it is the opposite way around if you actually think about it so the four chambers are the left atrium right atrium they form the top two Chambers left ventricle and right ventricle form the bottom two Chambers now do remember that pulmonary means relating to the lungs so if you have used the word pulmonary it means that blood must be flowing either to or from the lungs so we're going to start by picking up oxygen in the lungs it's going to be delivered to the heart to the left atrium via the pulmonary vein remember that veins bring blood to the heart arteries take it away so the pulmonary vein delivers oxygenated blood to the left atrium the left atrium contracts forcing blood into the left ventricle do remember that the valves open here and they are the bicuspid valves they open to allow blood to flow from the Atria to the ventricles the left ventricle contract forcing blood into an artery this is the aorta it is the main artery delivering oxygenated blood around the body so that blood goes and delivers oxygen the oxygen is removed and used by respiring cells clearly the blood will now be deoxygenated and it needs to return to the heart so it can be pumped on further to the lungs so it's going to return to the heart via a vein the vein is the vnea and it's going to take blood into the right atrium the right atrium contracts forcing blood through the tricuspid valves into the right ventricles the right ventricle contracts forcing blood into an artery this arter is clearly going to be flowing to the lungs so the blood can be oxygenated and this is why it is the pulmonary artery so that's our overview of blood flow around the body let's notice a couple of things things about the heart firstly that the walls of the ventricles are thicker than the walls of the Atria why because they need to pump a much higher pressure to deliver the blood much further after all they're delivering blood to both the lungs and the rest of the body all the Atria are doing is pumping to deliver the blood slightly lower a couple of centimeters lower into the ventricles why is the wall of the left ventricle thicker than that of the right again it's a distance thing blood from the left ventricle is going all around the body blood from the right ventricle is simply returning to the lungs your heart is here your lungs are here it's not too far why do we call this system a double circulatory system well that's because the blood passes twice into the heart for every once it travels around the body simple organisms such as fish have a single Loop so the blood just keeps passing from the gills to the heart around the body round and round and round um they're not as efficient as at oxygenating their bodies as we are you've got to know quite a lot about the various vessels that travel around the body just remember the arteries carry blood away from the heart and do remember that pulmonary means relating to the lungs and that hepatic means relating to the liver renal means relating to the kidneys so renal failure kidney failure hepatitis disease of the liver so these words if you do know what they mean it really helps because then when we're looking at what's the name of the vessel supplying the liver well it's hepatic it's coming from the heart which means it's an artery so it's the hepatic artery what is the name of the blood vessel entering the kidneys well it's coming from the heart so it's an artery it's going to the kidneys so it's renal so it's the renal artery the vessels leaving the organs well these have obviously got to return to the heart to become oxygenated so they're going to be veins so the vessel leaving the liver will be the hepatic vein just note the hepatic portal vein that's just um the name of the vessel which shunts blood from the digestive system to the liver and that's the only weird one you need to know about looking at coronary heart disease now the coronary arteries coronary means relating to the heart so the heart has its own special network of vessels which supply the heart with its own supply of oxygen it can't actually obtain its oxygen needs from the blood flowing through it has to have its own special set of vessels we call these the coronary arteries and they're famous because this is how people get heart attacks they get blocked they get obstructed and it does mean that oxygen can't reach the heart muscle so part of it dies which is what a heart attack is so first of all what factors increase your chance of getting coronary heart disease so that could be a sedentary lifestyle so lack of exercise could be your diet eating diets high in fat and sugar it could be inheritance so genes some people are just more susceptible than others because of genes that they receive from their parent parents it could be diabetes diabetes and coronary heart disease are very closely linked stress as well people shouldn't get too stressed cuz that can put a strain on their heart too in terms of what happens in coronary heart disease how heart attack might occur what you find is that fatty deposits get offloaded in the walls of the coronary arteries this obstructs the blood meaning that less oxygen can reach those respiring cells because they're not receiving enough oxygen they have to anerobic respire remember that produces lactate which solely poisons the muscle cells and then eventually there isn't enough oxygen so the heart dies and those cells die let's look at how a heart rate increase is brought about during exercise for example so clearly when you exercise you're going to produce more carbon dioxide why because your muscles are respiring more so carbon dioxide Flows In The Blood and it is detected by both the aorta and the coted artery this sends impulses or messages to the brain particularly the medulla part of the brain and specifically the accelerator nerve now that accelerator nerve causes an increase in heart rate so that more oxygen can be delivered to your muscles and so that more carbon dioxide can be removed looking now at the structure of arteries veins and capillaries so let's start with the arteries they have a narrow Lumen remember the Lumen is the hole in the artery it's like the hole in a straw so it's narrow this clearly means that blood is going to be forced through at a high pressure because it's at a high pressure it means that the walls of the arteries need to be very thick to withstand this pressure be nice and detailed here and state that they have thick muscle and elastic fiber walls looking at veins now in veins blood travels at much lower pressure this is because veins have a much wider Lumen the walls therefore need to be much thinner so they have thin muscle and elastic fiber walls they contain Valves and these valves prevent the back flow of blood because that blood sometimes travels so slowly it's liable to start backing up we don't want that to happen so the valves force it to move on in the right direction capillaries now capillaries SE are the tiny vessels that supply all our cells with oxygen they are one cell thick and this enables a very short diffusion distance and they have an extremely narrow Doom we're going to start by looking at the components of blood that will be red blood cells white blood cells plasma and platelets now remember plasmid is that liquid which actually acts as a suspension it carries these various cells around the body what sorts of things are transported in plasma these are going to be our products from digestion so things like glucose amino acids so soluble products there'll also be hormones being transported there'll be Ura from the liver which needs to be taken to the kidneys so it can be excreted and carbon dioxide platelets these are small fragments of cell they clot the blood at the sight of a wound so they're very important in forming scabs they convert soluble fibber enen into insoluble fibrin and that forms the mesh work which seals the wound looking more closely at red blood cells we need to look at those structure of our blood cells so we can see how they're so well adapted for their function they have a biconcave dish shape this means they're donut shaped and what this does is it maximizes the surface area to volume ratio ensuring that they can transport as much oxygen as possible the absence of a nucleus also means that there's more room for oxygen and do mention that they contain a pigment called globin remember ion is needed for hemoglobin production I mentioned that earlier in balanced diet and that hemoglobin binds to oxygen forming oxyhemoglobin next topic white blood cells and the immune system so let's first of all discuss how we prevent pathogen entry in the first place so remember our skin axle as a barrier our hydrochloric acid in our stomach helps to destroy pathogens our tears prevent pathogens entering our eyes and also your eyelashes but what happens once those pathogens actually enter our body enter our bloodstream clearly we can't stay ill forever and ever and ever so there are mechanisms in place which actually act to remove those pathogens the two mechanisms you need to know about are white blood cells and they are the phagocytes and the lymphocytes so starting with the phagocytes remember that they engulf or ingest pathogens by enclosing them inside a vacu and then digestive enzymes are secreted which destroy the pathogen the second type of white blood cell is the lymphocyte the lymphocyte is far more complicated and it works by recognizing the antigen on the pathogen it secretes lots of antibodies which destroy that specific pathogen and in this way the pathogen is destroyed now it has various modes of action which help to increase the pathogen destruction first of all it labels the pathogen making it easier for the fosite to recognize it and therefore engulf it it neutralizes any toxins produced by the pathogen and it also causes the bacterial cell to burst open on occasion lastly it makes the pathogens stick together with the answer relating to the lymphocytes notice that I use lots of keywords antigens antibodies for example try and include as many keywords as possible just shove them in your answer because if you look at mark schemes they'll be underlined as being worth a mark each so it's worth writing them in anyway don't just keep repeating yourself you need to insert lots and lots of keyword words here so how does the structure of an antibody allow it to work remember antibodies are made from white blood cells and they're involved with fighting pathogens and the immune response so remember that each antibody has a specific binding site The Binding site has a specific shape and therefore this can recognize very specific molecules and remember molecules which bind to the antibodies are known as antigens lastly vaccinations vaccines so obviously when you're going on holiday somewhere tropical you might need to go to the doctor to get some vaccines now what these are is they're injections containing either a dead weakened or attenuated form of the pathogen that means it contains the pathogens antigens now when there antigens enter your body clearly your lymphocytes are going to be set off and they're going to produce antibodies which actually respond to those pathogens and some of those lymphocytes turn to what's called memory cells those memory cells and rain in your body and therefore if you become infected at a later date with a much larger amount of that pathogen there are memory cells already in place which can secrete antibodies very quickly much faster much sooner and in a much larger quantity and what that means is that pathogen can be destroyed before it can take a hold of your body so the whole point of vaccination is to inject a harmless version of that pathogen so that if you accidentally become infected at a later date it can be destroyed before it can take hold so let's look more closely at some vaccinations which are made so dead pathogens are used to immunize against hooping cough we used a weaken form of the pathogen to treat measles and also tuberculosis and then lastly we just inject the antigens themselves when we're treating influenza look more closely at digestion then so we know that's the removal of feces from the anus now feces which are incredibly watery we know is diarrhea which is very very unpleasant how do we treat diarrhea well there's not an awful lot we can do we do tend to recommend oral rehydration therapy and that contains a mixture of water and mineral salts and this is to prevent the dehydration which is associated with diarrhea because obviously if you're losing lots of water feces you're not taking in enough water so that needs replenishing chalera is a disease which is a full it is diarrhea to the extreme now this is caused by bacterium and what happens is that bacteria produces a toxin this toxin increases the loss of chloride ions in the small intestine which leads to a really strong osmotic effect within the gut causing massive amounts of water loss this causes diarrhea dehydration loss of salts from the blood and I know this sounds mad but it can even lead to death chora is a major cause of death in developing countries moving moving on to the breathing system so we are looking at our lungs and all the vessels relating to that so we're going to start with our mouth it leads down to our windpipe which we're going to have to call the tracha the tracha branches to form two Brony further branching occurs which is the bonches and that ends in lots of airs which we call alvioli and they're surrounded by a network of blood capillaries now if you actually think about it it is very much like a tree because the traa is represented by the trunk the big branches are the Brony smaller branches of the bronchol the alvioli are similar to the leaves so do bear that in mind now we need to talk about how those Brony and bronchial are kept clean that's due to the presence of two types of cell the Goblet cell and the ciliated cell the Goblet cell first of all secretes mucus that mucus is good because it traps bacteria pathogens and it stops them from entering your lungs this is when the cyia come in because remember they have have hairlike projections which waft and they waft that mucus which is covered in bacteria up to your mouth where it can be swallowed and destroyed by your stomach acid now what is ventilation well that's simply taking air into and out of your lungs let's look in great depth now at an inhalation so a breath in so first of all the external intercostal muscles contract the ribs move up and out the diap contracts um what this means is that it flattens and together all these processes increase the volume within your thorax because there's an increased volume clearly the pressure will decrease because the same amount of air is now present in a larger volume and this means that air will be sucked into your lungs causing your lungs to inflate now we want to take an exhalation we want to breathe out so the opposite takes place this time the internal intercostal muscle mus contract the ribs move down and in the diaphragm relaxes this has the effect of reducing the volume inside the thorax the pressure increases relative to the pressure outside the body and therefore air is sucked out of your lungs and your lungs deflate a small thing on looking at the composition of gases in your lungs clearly air that you inhale will contain more oxygen than the air you exhale why because the whole point of breathing in is to get oxygen into your lungs so it can diffuse into your blood and then be taken around your body for respiration respiration obviously produces carbon dioxide which is why when you breathe out the air contains more carbon dioxide than the air you breathed in looking more closely the alvioli because this is where gas exchange takes place where oxygen moves into the blood carbon dioxide leaves we need to look at the adaptations of alviola for gas exchange so clearly they have a very large surface area they are thin which gives you a short diffusion distance for that oxygen and carbon dioxide to move across they are moist which helps the gases to dissolve and I can't think of anything else so that is the adaptations of avioli done the next topic we need to tackle is respiration both aerobic and anerobic respiration remember it's the process carried out in mitochondria which releases energy so what is this energy used for well it's used in cell division it's used to build up large molecules from small molecules it's used in active transport and it's used to contract our muscles let's look at the equation for aerobic respiration now so you need to take oxygen into the body you need to add that to glucose an arrow and then what's produced is carbon di oxide and water and energy is released again you need the balanced symbol equation here and it's again all the sixes I hope you've noticed that photosynthesis and respiration are the same equation just reversed so in terms of the Bal SYM equation you're looking at C6 h126 plus 602 AR 6 CO2 + 6 H2 plus energy in a square bracket if you so wish now aerobic respiration involves the use of oxygen and that's the type of respiration that we carry out ordinarily now sometimes we have to carry out anerobic respiration which tends to be when we've exercised and when we can't take enough oxygen into our bodies and this involves the incomplete breakdown of glucose and we find that lactate is produced instead now lactate is pretty poisonous it's what gives our muscles cramp and we need to remove that lactate so we have to take in more oxygen which we call the oxygen debt in order to break down that lapate to ensure the glucose is completely broken down now there are two places where anerobic respiration takes place that you need to know about so I've already mentioned one which is in your muscles so I've given you all that information about the oxygen debth it's when you can't take enough oxygen into your body and that's because you've been doing something pretty strenuous like sprinting you also need to know about anerobic respiration in yeast remember that yeast is a type of fungus and yeast anerobic respires and it breaks down glucose into ethanol plus carbon dioxide and these are very useful industrial processes because remember the carbon dioxide is used to help bread rise and that the ethanol is used in beer making moving on to excretion so both in plants and humans obviously when we're talking about humans we'll be really looking at the the kidney let's start by looking at the definition of excretion it's the removal of waste products of metabolism from the body looking at excretion in humans what sort of substances are excreted first of all sweat from the skin Ura from the kidneys carbon dioxide from the lungs do note that feces are not excreted they are digested and I already touched on this in the nutrition part of this video so remember with the kidney we have the nephron this is when you take the kidney and you zoom in and you see that there's a Bowman's capsule followed by the proximal convoluted tubal the loop of Henley the distal convoluted tubule and then lastly the collecting duct so let's have a look first of all what happens at the Bowman capsule that is a process of ultra filtration ultra filtration is when small molecules are filtered out of the blood into the Bowman's capsule such molecules include Ura sodium and chloride ions glucose and water and remember that these are forced out under pressure so how does the structure of the bonus capsule and the blood vessel flowing into it the gulus actually Aid this ultra filtration the reason is is because the blood vessel entering the Glarus is wider than the one leaving this creates a huge amount of pressure which actually forces those small molecules out of the blood into the Bowman's capsule which molecules don't enter the B's capsule well that's proteins why because they're too large to pass through the basement membrane now we've end Ed the proximal convolu tual we need to know what happens there the process of selective reabsorption occurs here now this is when all glucose some ions and none of the Ura is removed from the proximal convoluted tubal back into the blood this is occurring against the concentration gradient so it requires energy now we're moving on to the collecting duct cuz we now need to look at Water reabsorption and this is all to do with osmo regulation now osmo regulation is the control water content in the blood and obviously sometimes we drink lots so we need to wee a lot sometimes we drink very little so our wee will be very very concentrated and small in volume and now we're going to look at the mechanisms involved in controlling the amount of urine we produce so let's start when we've not had very much to drink so overnight for example on a hot day clearly our bloodstream will contain little water that passes in the blood to your kidney specifically the collecting duct and it basically tells the collecting duct to be more permeable to water so it adds lots of channels into the collecting duct which enables lots of water to leave the collecting duct and be reabsorbed back into the blood this means that there's far less water left over to create urine so in this situation urine is very yellow it's concentrated and low in volume let's look at the opposite effect so when we have had lots and lots to drink makes the walls of the collection du less pal water water meaning that more water stays inside the collecting duct and that less is available to be reabsorbed this means that there is more water flowing from the collecting duct to the bladder and therefore resulting urine is high in volume not very concentrated and very pale in color just to touch on the name of some key vessels The Vessel linking the collecting duct to the bladder is known as the Ura The Vessel taking urine out of the body so from the is known as the urethra and if they ask you in men what two substances does the urethra transport out of the body that would be both sperm and urine definitely not water some people in the past have written water that is really silly that is not the answer looking at the general structure of a kidney you can see the outermost layer is known as the cortex the middle layer is known as the medala and then the Ura passes out and then we've obviously got the renal artery and the renal vein supplying and removing blood we're talking about the nervous system here so let's start by looking at again what is a stimulus it is a change in the environment now that change in environment is detected by various sense organs and you need to be aware of their names and what they're actually receiving information about starting with the ey that receives light energy the ear receives sound energy and kinetic energy the muscles in your skin receive kinetic energy your tongue receives chemical energy so your nose it also receives chemical energy why because that's chemicals in food and that's what you smell and then lastly your skin receives kinetic energy and heat energy so there are two types of communication you need to be aware of the nervous communication and hormonal communication so hormones are chemicals which travel in your blood they send signals and messages to I parts of your body whereas the nervous system involves the use of electrical impulses so let's have a quick comparison between the two first of all nervous system is much faster than the hormonal system clearly electrical impulses will get to their location much faster than hormones traveling in the blood the nervous system involves very localized responses so the electrical impulse will be locating a very specific effect to muscle whereas the hormonal system has far wider spread effects the the nervous system responses are shortlived whereas the hormonal system involves much longer lived responses and the last thing which I've already mentioned but just to really point out to you the nervous system involves electrical impulses whereas the hormonal system involves the use of chemical Messengers so we're going to take the nervous system in Greater detail now so let's first of all look at what a stimulus is so that's a change in the environment and obviously that causes the response the nervous system brings about do be aware of of what the central nervous system is that consists of both the brain and the spinal cord let's go through all the steps involved in a regular nervous response one which does not involve a reflex action so I'm going to use picking up a book as an example so first we need to listen to stimulus which is seeing or viewing the book this is picked up by receptors and these receptors will be in your eyes your photo receptors on your retina they'll send electrical impulses along your sensory nve onto your central nervous system electrical impulses then pass along your motor neon to your affector and this will be muscles or glands and in this particular case it will be muscles which will contract to pick up your book remember an effect is either a muscle or a gland so a muscle responds by Contracting a gland responds by secreting hormones don't forget the role of the sinapse so the sinapse is the gap between two neurons and this is where a neurotransmitter is released so the neurotransmitter diffuses across that synaptic gap that synaptic CFT and binds to the post synaptic membrane so your electrical impulses change to a chemical or a neurotransmitter and then change back to an electrical impulse at a sinapse looking now reflex actions remember these are faster and they are involuntary so they do not involve a conscious part of your brain and it tends to be in response to something painful so taking putting your hand in the oven and accidentally touching one of the shelves which is hot this would trigger a reflex action so the stimulus system time would be the high temperature from the oven tray your receptors would be on your fingers which would receive that information about it being too hot electrical impulses would then flow again flow along your sensory neuron to your relay neuron this time so we're not involving the conscious part of our brains the electrical impulse passes along the motion to your affector which will be a muscle in your finger which contract to remove your hand or your finger away from that heat source right we're going to look now at the eye you need to know lots about this it's a very important sense organ so I'm going to start by running through its various structures and their roles so first of all light enters the eye and it hits the cornea so the cornea's role is to refract the light to bend that light as it enters the eye the light then has to pass through the pupil so the pupil's role is simply to allow light into the eye the size of the pupil however is controlled by the iris and that is the colorful part of your eye mine's brown other people's are green or blue and the iris has circular and Radial muscles which will actually help it control the size of the people we'll go into that in slightly more detail further on so now light has entered the eye it now hits the lens the lens's role is to refract that light further in order to focus it on the retina the retina contains photo receptors these are cells which are sensitive to light and they are called rods and cones rods are sensitive in very dim light and Cones are sensitive to color then we have the optic nerve and that converts those light signals into electrical impulses which can be carried to the brain where they can be computed then we have a blind spot the blind spot is simply the place on the back of the eye where the optic nerve leaves the eye because clearly there can't be any photo receptors where you have the optic nerve the FIA is a place that is very concentrated with cones so it's very good for seeing color we need to look a bit more now at the lens so I've already told you that lens the lens focuses light onto the retina it does this by a process of accommodation so accommodation is all about focusing light from different distances away so that an image can be formed on the retina so let's look at what happens when we're looking at an object far away so when it's far away it's going to be the light is going to be coming into your eyes fairly parallel which means it doesn't need refracting very much therefore the lens needs to be thin in order to do this the cery muscles relax and the suspensory ligaments are Tor and this means you have a very nice thin lens so it doesn't refract the light too much looking at an object really close to us now the light rays are going to be coming in at far greater angle therefore the lens needs to do far more work in order to focus light onto the retina in order to do this the lens needs to be fat so in this case our CER muscles contract and our suspensory ligaments slacken off meaning that our lens is nice and fat so that's the way in which we focus on light at different distances away we now need to look at the pupil reflex so the pupil changes its diameter dependent on light levels so if there's lots of light the pupil needs needs to be narrower and that's to prevent damage to the retina because too much light entering the eye will damage the retina if we're in a dim or dark room the pup obviously needs to be nice and wide in order to allow as much light into the eye as possible we can use this response as an example of a reflex action so previously I told you all the steps involved in a reflex action and we're just going to use those steps but we're going to apply them specifically to this example so I'm going to use an example which is that we have walked into a very bright room so the stimulus will be lots of light the receptor will be the rods and cones on your retina then the sensory neuron will pass along the optic nerve to the brain and there will be a relay neuron then we have a motor neuron which is also passing along the optic nerve and it will end in an affector and in this situation the effector is the muscles which you find in your iris so your circular and Radial muscles and you'll find that your circular muscles will contract and your radial muscles will relax and that will act to narrow or constrict the pupil now looking at a separate hormone which is adrenaline remember that is the fal flight hormone it's released in bucket loads when we're under conditions of stress and it's good to imagine a really angry cat when you're thinking about the effect that adrenaline has on your body so this cat's hairs have stood on end and that's because it wants to appear scarier to its opponent its pupils have dilated and that's to allow more light into its ey so it can see more clearly it heart rate not that you can see this but adrenaline has caused its heart rate and breathing rate to increase why the heart rate increases to deliver blood faster around your body your breathing rate increases to allow more oxygen into your body for respiration blood is diverted from your digestive system to your active muscles and your arm arms and your legs and that's so you can either fight or run away if needs be so yeah try and remember the cat at least for the hair standing up on end and the pupils dilating another thing to do with homeostasis we're looking at blood sugar so how do we decrease our blood sugar levels after we've eaten well we release a hormone called insulin now insulin is secreted from the pancreas and it causes glucose to be converted from its Sol soluble form into glycogen which remember is insoluble and that can be stored in the liver let's look at the role of the skin now so first of all the skin acts as a barrier and that actually helps prevent pathogen entry because we often have viruses and bacteria landing on us but because the skin is such an amazing intact organ it does actually prevent those microorganisms entering our body it's also waterproof which is why you don't swell up when you go swimming it forms a very tough outer layer just generally to prevent you from physical harm if you knock into something it's a sense organ for pressure touch and pain and lastly it controls our heat loss how by either sweating or the hair stand up in order to trap some insulating air close to our bodies let's now look at what happens when we're too hot and too cold so we're looking further at the homeostasis topic which remember is all about controlling a steady internal environment within our bodies so let's start by looking at when we are too hot well first of all an uncomfortable thing happens which is that we sweat the reason being that when sweat evaporates it acts to cool the body face the dilation occurs and that's the arterials in our face they dilate they become wider what that means is that the blood flows closer to our skin and therefore heat can be radiated more easily and also when we're too hot the hairs lie down on our body on our arms and that's just so that less insulating air is trapped close to our skin because remember air is a good insulator it keeps you warm so by making our hairs lower it means we're kept less warm so if we're too cold clearly our hairs will stand up on end so that more insulating air is tra close to our skin and that actually acts to keep us warm we shiver the reason being that that muscle contraction releases heat energy lastly the opposite of Vaso dilation occurs Vaso constriction the arterials in our face constrict they narrow bringing blood away from the surface of our skin so less heat is radiated let's look at how blood sugar levels are controlled and we need to know lots of hormones and the effect that they have on blood sugar we're going to take two scenarios so first of all after a clearly your blood glucose levels will increase because you've just eaten it's important that we reduce those blood glucose levels so the pancreas remember which organ does this so it's the pancreas releases the hormone insulin and that insulin travels to the liver and causes it to convert soluble glucose into an insoluble compound known as glycogen and as you can see blood glucose levels will therefore have decreased after exercise or when you haven't eaten for a period of time clearly your blood sugar levels will have decreased so glucose levels have decreased the pancreas again is involved and it releases a hormone this time called glucagon and please notice the spelling of glucagon and iogen they're incredibly similar sounding words and it's so essential you spell them correctly because I know there'll be a point in the mark scheme being like reject if they've spelled it wrong so make sure you take pains to learn that spelling correctly this time the glucagon travels to the liver and it causes the insoluble glycogen to be converted back into soluble glucose which then gets released into the blood and subsequently you see an increase in blood glucose levels which is all good now famously a disease when you don't control your blood sugar levels appropriately is called diabetes and there's type one and type two type one tends to be the one you get as a child and we call it early onset for this reason and it is inherited so you get it through your Gene so you inherit it from your parents and here you'll have to do insulin injections because effectively your pancreas isn't producing enough insulin in terms of symptoms so how you might know that you have diabetes first of all you'll get excessive thirst so you'll want to drink all the time as a consequence of that you'll produce lots of urine because you've taken on so much water and liquid you get increased hunger sweet smelling breath and the biggest giveaway is if the doctor tests your urine and there's glucose in the urine that can be an indicator of diabetes because really we know that the glucose should have been reabsorbed in the proximal convoluted tubal of the kidney so glucose in the urine would indicate that there's something wrong so we're going to take plants first of all and we're going to look at tropisms first of all what is a stimulus and that is change in the environment so what sort of stimuluses do plants need to respond to clearly they need to respond to the amount of light and they actually also respond to gravity so we call a plant's response to light a phototropism a plant's response to gravity is known as geotropism so how do organs of a plant react to various tropisms so let's take phototropism first of all clearly a stem shows positive phototropism why because it grows towards the light Roots show negative phototropism because they grow away from the light let's look at gravity now Roots obviously show a positive geotropic response because they grow down in the direction of gravity whereas stems show a negative geotropism because they grow away from Gravity looking more closely now at how these changes are brought about to the stem and The Roots we need to understand the role of orins so what are orins well they are plant hormones let's now explain how a plant stem may bend towards the light towards the sun cuz you do see particularly sunflowers Bend towards the sun that's because the orins concentrate on the side furthest from the light source this causes cell elongation on that side so the cells get longer and therefore the plant then bends towards the light they do like to show you various experiments and an important part of this will be the kopti which are these really boring little ceilings now note that they are serial seedlings and they are simple plants used to investigate tropisms so do be aware of how they respond if you Cho their tops off if you put a mic sheet in between the top of the stem and the bottom of the stem if you use eggar jelly you do need to know different responses lastly the role of a cinat this is another boring piece of equipment so a Clin is a device used to remove any stimulus so for example it negates the effect of gravity or negate the effect of sunlight drugs a scary topic because if drugs are misused they can cause lots of issues but the one thing to notice is that drugs aren't all bad I think people tend to think of heroin cocaine ecstasy Etc when we talk about drugs yes indeed these are drugs but remember there are plenty of therapeutic drugs things like paracetamol aspirin morphine and these have all been proven to really help human health to alleviate symptoms produce pain relief so so it's not that all drugs are bad it's just that you need to remember that a drug is actually just a chemical which affects the body and there's so many different categories of drug one very important category includes the antibiotics crucially these are given to you if you have a bacterial infection so they're used to kill bacteria and they do this by damaging the bacterial cell wall meaning that it bursts and can no longer replicate they do not work on viruses this is commonly misunderstood people go into the doctors with a cold andex antibiotics but unfortunately for them these colds are caused by a virus its name is Rhino virus and if you ask for antibiotics the doctor simply won't give them to you because it will not have any effect whatsoever increasingly though we're seeing antibiotic resistant bacteria which is incredibly alarming so antibiotics are being given to treat these bacterial disease where historically it would have killed all the bacteria but you're finding the bacteria are surviving and the antibiotics are having no effect and this is all due to Natural Selection because some of those bacteria mutate and some of these mutations mean that the bacteria is no longer affected by the antibiotic clearly these bacteria Will Survive they'll reproduce and before long you end up with an entire colony of bacteria which is resistant to an antibiotic which is becoming a real concern it's incredibly scary so how can we reduce the chance of antibiotic resistance first of all complete your course and what that means is if your prescribed antibiotics you must finish the course you mustn't just stop taking them the moment you start feeling better so if the course is 3 weeks long then you started feeling better after 2 days doesn't matter you need to complete the course and secondly you should only be prescribing antibiotics when essential so historically pigs and things used to be given antibiotics even when they weren't sick just to stop them getting sick in the first place and this was responsible for lot of the resistance strains that we see today so you need to know that antibiotics don't work on viruses um and that's not just because they don't have a cell wall in the way that bacterial cells do but it's also because viruses work in a very different way to bacteria so they actually infect their host they get inside the cell and so they're incredibly hard to spot by either the immune system and the antibiotic we are now moving on to reproduction so we'll start by looking at the difference between sexual and asexual reproduction hopefully sexual reproduction is nice and straightforward clearly you need two parents and it involves gametes remember the gametes are eggs and sperm because these are sex cells so the sperm and egg meet at fertilization the first cell formed is known as a zygote and then it divides by mitosis to form your multicellular organism and clearly due to the production of gtes these Offspring will be genetically varied which is a really important thing to note with sexual reproduction is that it produces genetically varied Offspring so if the environment changes it means that some individuals will be better adapted whilst others will be less well adapted and that's where natural selection comes in but we'll come across that later on in this video with asexual reproduction you only need one parent it's a much quicker process you end up with genetically identical Offspring and this is why it's good when conditions are unchanging it's a great way of quickly producing large numbers of identical Offspring which we call clones there is no gametes no fertilization and no zygote is formed some key definitions now so fertilization that's obviously the joining of an egg and a sperm a zygote is formed and remember it under go mitotic cell division so lots of mitosis takes place to form two cells four cells8 cells 16 cells so if they ask you how a 32 cell embryo is formed spam egg gamet make sure you include lots of key words join at fertilization a zygote is formed it divides by mitosis to form two cells four cells 8 cells 16 cells 32 cells and that's how you get lots and lots of marks by not writing very much by including key words such as gtes mitosis Etc so in order to look at reprodu in Plants we obviously need to look at the structure of a flower you need to know the names of the different parts of the flower and that know that the flower is separated into both male and female parts so the male part consists of the anther and the filament so the filament is actually the thing that supports the anther whereas the anther contains the pollen grains and they're essential because they're the male gamt in a plant the stigma and the style and the ovary are the female parts of the plant the collective n for them is the carpal and everything else is just extra detail that will actually help attract an insect or will help with the wind pollination aspect of sexual reproduction in plants so now we know about the structure of the flower that will help us understand what pollination is fertilization etc etc so we're now going to look at seed formation it's important that you know every step involved in this because you could be asked to five marker on this so first of all pollen from a male anth will land on the female stigma a pollen tube will grow down the style and digestive enzymes will help break down the wall of the ovary at this point the pollen will meet the ovil which is the female gamet and fertilization takes place the ovil then goes to form the seed the ovil wall forms the seed coat and lastly the ovie wall will form the fruit so make sure you list those last steps involved but first of all let's understand what we mean by the term pollination you've got to be super specific here so remember that the male gam in a plant is pollen the female gamt is the egg but all pollination is is transferring that pollen to a separate plant so your perfect definition here is that pollen produced on the anther which is a male part of the plant is transfer to the stigma which is the female part of the plant on a second plant and the perfect definition will pop up now so you can see exactly what you need to write self-pollination obviously is the name suggest that's when the plant does it itself so that's where pollen from a single plant will land on the stigma of the same plant fertilization now so remember Fertilization in humans is all to do with sperms and eggs fusing this time as we talking about plants it's about the pollen fusing with the egg looking now at the difference between insect and wind pollinated plants so let's when we're talking about the insect pollinated one think about all the ways in which these flowers these plants make themselves appealing to Insects so first of all they have bright large colorful petals these are flag light structures and they literally draw the insects attention so they're like right come and pollinate me secondly they have a nectar the nectar is essential because that's actually why the insect is visiting the plant in the first place it's not doing the plant a favor it doesn't give her a damn about the plant it's simply trying to obtain the sugar from that nect which is why insect pollinated plants have a nect they have enclosed stigma and anther and what that means is that the insect is forced to rub against the pollen or the stigma when they enter the plant to find the nect Tre so they're more likely to pick up the pollen they have a strong scent so that the insect can smell them and that's everything I can think of looking now at a wind pollinated plant it's going to be very different from an insect pollinated plant largely because it's the wind blowing that will actually blow that pollen away to a separate plant which is why it makes sense therefore that the anther are very exposed so that when the wind blows the pollen will literally blow off the plant and be carried by the wind elsewhere they tend to be dull colored have small petals no scent for the same reason because the wind can't see these things cuz it's wind so there's no need to have flag like petals there'll be an absence of anory again because the wind doesn't need sugar they have small petals small pollen grains feathery stigma um just list these all out and you'll be fine next up we need to look at germination so first of all what is germination this is obviously what happens when you plant a seed and it effectively pops out and starts growing but you need a detailed answer so first of all the seed coat bursts the radical is the name for the small root that appears and that starts to grow downwards a small Sho will appear and obviously that starts to grow upwards and the seeds food store is used up because the plant can't photosynthesize until it grows its first leaves in terms of the conditions needed for photosynthesis remember the pneumonic wow standing for warmth oxygen and water so all these things are needed in order to enable a seed to germinate moving on to the male and female reproductive system in humans now and there's a new emphasis for you guys on the various roles of different components of the reproductive system so let's start with the female reproductive system so starting from the beginning you've got the vagina the entrance to the uterus is the cervix and then branching off the uterus you've got the Fallopian tubes or the OV ducts lastly ending in the ovaries so what is the role of the ovaries well it's to manufacture eggs the role of the fallopian tube is to deliver eggs to its entrance so that's where fertilization takes place uterus is obviously where the zygote in beds it develops into an embryo into a growing fetus and it supports the embryo through the placenta the cervix is simply the entrance to the uterus and the vagina is a passage leading out of the woman and it's where the penis inserts to deposit semen during sexual intercourse and lastly the urethra it's not really to do with the female reproductive system but do remember it's a separate tube and it transports urine out of the body so it links to the bladder please don't think that a woman urinates out of her vagina lots of people seem to be very confused on this no there are two separate passageways moving on to the male reproductive system now so we're going to start by looking at the testes or testicles these manufacture sperm and also the hormone testosterone they link to the urethra via the sperm duct the sperm duct is simply a tube which transports semen from the testes to the urethra the urethra is a tube which links the sperm duct to the outside of the body and in men it transports both seen and also urine and then lastly there are some glands such as salal vesicles some of you may not need to know this the prostate gland and these just contribute fluid to the semen so that it's not just made up of sperm lastly the penis it passes urine out of the body and deposits semen inside a woman's vagina now let's be sensible about the topic and know being silly now we describ desing the passage of sperm in the female so clearly I just said the sperm is deposited in the vagina it swims through the cic into the uterus and lastly it swims all the way to the entrance of the overd duct or the floan tube where fertilization actually takes place so the swim has a very long way to swim the role of the placenta remember this is a huge organ which actually supports the growing fetus so it provides the fetus with oxygen digested nutrients such as glucose and amino acids to help it to grow and it also removes waste products such as Ura later on in pregnancy it takes over the role of producing the hormone progesterone and progesterone is a good place to link because we now need to look at the various hormones involved in the female reproductive system so we're going to start with FSH now FSH is produced in the P gland and it stands for follicle stimulating hormone and that's a really good way of actually helping you know what it does so its role is to stimulate the follicle the follicle is the egg so it role is to mature the egg in the ovary LH is also made in the py gland it is lutenizing hormone and its role is to cause ovulation now ovulation is the release of an egg from an ovary next up estrogen estrogen is produced by the ovaries it's responsible for secondary sexual characteristics in females so those are all the changes that occur during puberty such as breast development hips widening pubic hair armpit hair all those sorts of things sexual drive develops its other role is to inhibit FSH so actually slows the production of FSH which makes sense really because if you've already had an egg released you don't want to be maturing any more eggs because presumably you're going to be fertilizing that first egg and it's last and very important role is to repair the uterus lining so it causes it to thicken in preparation for a fertilized egg progesterone now progesterone is produced by firstly the Corpus Lum the Corpus Lum is just the leftover HK effectively when the egg is ovulated it's the leftover structure that produces progesterone later on in pregnancy the placenta as I've already told you takes over the roll and its role is to maintain the thickness of that uterus lining without a thick lining a woman will miscarry because it really needs to be thick in order to support the growing fetus and then because we need to mention men testosterone its role is to support the development of secondary sexual characteristics so again the puberty changes this includes pubic hair armpit hair widening shoulders bigger muscles voice breaking or deepening sexual drive develops spun production occurs now a fairly unpleasant topic which is to do with STI so these are sexually transmitted infections and as the name suggests it's an infection transmitted by bodily fluids through sex good examples here include HIV herpes is another example you could also have chlamidia or gona I have no clue how to spell those so I'm not going to write them here this is becoming an increasing problem so STI is being transmitted by people and it's something which needs to be prevented and there's lots of ways in which STI can be prevented whilst people can still have sex so that includes obviously wearing condoms so that barrier method not only prevents pregnancy but also prevents STI there's testing so that's a way of just checking to see if you have an STI so you don't continue to have unprotected sex and carry on spreading it it's also good to have some knowledge of partner sexual history so they so you can work out the likelihood of them having an STI I realized this would be a very awkward conversation to have but it's all about knowledge and information the more you know um the more you can protect yourself and things like worldwide education programs so HIV is very prevalent in Africa and a large part of the problem with stopping it spread is the fact that people don't understand that it is spread through unprotected sex so it's all about educating people so they know what's happening and then lastly you can provide things like antibiotics vaccinations and antiviral drugs just to help treat the STI so going into more detail about HIV remember that stands for human immuno deficiency virus which later can become AIDS which is an incredibly serious disease now I've already told you it's spread by unprotected sex obviously that needs to be with an infected person and sadly it can actually be spread from mother to child across the placenta or through milk so feeding their child and then syringes so drug users are at risk of getting HIV because obviously if they share syringes which is a very disgusting practice anyway but if you share a syringe with someone with HIV their contaminated blood will obviously be injected into you and so that can cause the SP of HIV that way so really really unpleasant so what does HIV do well I've already told you it can lead to AIDS now AIDS is so scary because it damages the immune system and remember the immune system is all to do with fighting pathogens so fighting bacteria and viruses and what it does is it actually reduces your white blood cell count and specifically it reduces your lymphocytes are responsible for producing antibodies so when you're infected with HIV the number of antibodies you can produce seriously decreases we need to start by looking at some key definitions such as genome and that is the entire DNA belonging to an organism so we're focusing on on the nucleus of a cell remember that the role of the nucleus is to control the activities of the cell and it does this because it contains lots of genetic material So within the nucleus we know that there are chromosomes there are 46 chromosomes which is a diploid number because remember there range is 23 pairs remember half the number of chromosomes is known as aoid number however I digress I don't really want to talk about that now so the chromosomes are made up of DNA you need to know the definition of a gene a gene is a section of DNA which codes for a particular protein looking at the difference between RNA and DNA the main difference here is the sugar involved so RNA has ribo sugar as opposed to DNA's deoxy ribos and lastly there's a change in base there's no thyine in RNA you've got to learn that this time it's urasil so adenine pairs with uracil in RNA and cytosine and guanine still pair up RNA is single stranded compared with DNA's double strand so we don't see a ladder with RNA we just see one side of the ladder effectively let's move on to looking what a codon and anticodon is so a codon is just a fancy way of describing three bases which are found on the MRNA molecule and they correspond to a single amino acid so remember protein synthesis is all about making new proteins it's about sorting out the arrangement the sequence of amino acids so they can actually produce a particular protein and we're going to talk about how those amino acids line themselves up in the correct order AKA protein synthesis mRNA are messenger RNA because it carries the message from the DNA and now needs to leave the nucleus so it leaves via nuclear pore and attaches itself to a ribosome which we find within the cytoplasm hence the summary definition of ribosome's role is that it carries out protein synthesis so the MRNA attaches to a ribos and this is where translation begins so there are t tRNA molecules within the cytoplasm and they have complimentary anticodons so they'll have the three bases which compliment B pair up with the MRNA exposed bases and on the other end of that TRNA molecule will be an amino acid and effectively the TRNA brings the amino acid to the MRNA the codon will match up with the anticodon and we have our first amino acid in place then the next three bases on the MRNA will be red and a different TRNA molecule will bring probably a different amino acid along because if there are different bases it will correspond to a different amino acid so the second amino acid has been brought and they attach to each other using a peptide bond so that is the start of our protein chain um it keeps going and keeps going and eventually a stock codon will be reached and that's just three specific bases which correspond to no amino acid whatsoever and that will signal the end of that growing protein chain don't forget that hloy means containing one set of chromosomes so in humans that is 23 diploid means containing two sets of chromosomes in humans that is 46 let's look at mitosis and meiosis now so remember they're both types of cell division but they're used for making very different things so meiosis is used to make gametes so that means it's used to make sperms and egg mitosis is a completely different type of cell division you need to learn that it's used in cloning asexual reproduction and the growth and repair of cells so for example if you damage yourself you cut yourself it will be mitotic cell division which replaces those cells if you're caring at asexual reproduction so something like a strawberry Runner producing baby strawberry plants that will involve mitosis the reason being is that it creates genetically identical Offspring I don't think you really need to know this but some teachers like to just chat slightly about the different stages involved in mitosis and meiosis I'm really only going to give you their names and the first stage is prophase the second second stage is metaphase then anaphase and finally Tila phase but this is a revision video and I'm not willing to talk about it anymore at this point because I don't think it's necessary for lots of you so let's look at the differences between myosis and meiosis I always do this as a table because it allows me to make a direct comparison so look at the number of cell divisions first of all that will be one cell division in mitosis two cell divisions in meiosis the number of daughter cell now so that's the number of cells produced once this cell division has taken place in mitosis you're looking at two daughter cells in meiosis you're looking at four daughter cells I've already touched on the sorts of cells that I've produced but just to recap mitosis produces genetically identical daughter cells meiosis produces genetically varied daughter cells which makes sense if we're using mitosis in cloning that's genetically identical we're using meiosis in making gametes it makes sense that we want asp and egg to all be different to each other and do notice that the gametes will contain aoid number of chromosomes whereas the daughter cells produced by mitosis will contain a diploid number so differentiation is the process whereby cells become specialized for example nerve cells now a stem cell is a cell that has the potential to divide many times without being differentiated we're going to talk about genetics now so we need to know the definitions of lots of very key important terms and then I'm going to show you how to do Pit squares and pedigree analysis so let's start by looking at what a gene is a gene is a section of DNA which codes for a particular protein now there are different genes which control different traits so for example eye color now different forms of the same gene we call alals so you must learn that definition so if we take eye color for example different Al for eye color could be blue or brown you must now know the meaning of the word genotype the genotype is the alol an organism has so for example when we're talking about blue eyes it's two small bees if we're talking about brown eyes it could be Big B little B so when you ask for genotype you must provide letters the phenotype is different this is the physical appearance of a particular trait so if you asked for the pheny type of this eye color the answer here is blue so the genotype would be little be little be the phenotype would be blue eyes so be very aware of that distinction next up we need to know the meanings of homozygous and heterozygous homo means same so it means having two of the same Al whether that's two big bees or two little bees it doesn't matter as long as they have the same case so they both need to be upper or they both need to be lowercase and that is the meaning of the word h zygus heterozygous means different so that means containing different Al so in the case of I color that would be a big b and a little B now a dominant trait requires simply the presence of one Ali for it to exhibit itself in an individual so Brown is an example of a dominant trait because you can have two big bees or two a big be and a little be and the trait will still appear recessive requires the absence of the dominant alel so a recessive trait could be blue eyes cuz you need two little bees for example a blue-eyed mother and heterozygous Browne father decide to try for children what is the probability that the children will have blue eyes so let's work out what we have here first of all blueeyed remember blue is a recessive trait which means that her genotype must be small B small B we've been told that the father is brown eyed which means he could be Big B small B or Big B Big B but the fact that he is heterozygous tells us that he must be Big B small B and not Big B Big B so I'll show you how to lay out your answer and this is the method you should always use so start by writing mother and father at the top and we know how much I love tables so you're going to write in your table phenotype genotype and lastly gamy remember these are sperm and eggs so the phenotype this is the physical appearance we can see from the description that the mother has blue eyes and the father has brown eyes the genotype so these are the AL that each parent has I've already written these out so it's small B small B big little be the gamt just split these up because this is saying what the exit sperm will be so just write out what you vote on the genotype layer but put circles around them to show that they're gamt because here are the sperm and the mothers are eggs and now we need to do the punet square so mother father I don't know why my iPad sometimes undoes what I've done already so she's small B small B he's Big B little B that's cross them so big b small B Big B small B small B small B and therefore both of these will have blue eyes both of these will have brown eyes so as a percentage likely Hood it's 50% will have blue eyes and 50% will have brown eyes cystic fibrosis is a recessive disease a car mother and a car father decide to try for children what is the probability that the child will have cystic fibrosis so it's recessive which means to have the disease you need this genotype small C Small C it doesn't matter what letter you use to assign by the way but I'm using C here because of cystic fibrosis a carrier mother and a carrier father that automatically tells me that this is their genotype and you must learn that they're effectively heterozygous if they are carriers so we've worked out their genotypes so we're ready to do the genetic cross by writing mother and father at the top again phenotype genotype and gametes in the T T the phenotype is that they are both carriers their genotype we know is heter so it's Big C Small C this means that half of her eggs will be Big C half of them will be small C and the same with the sperm make sure you really show a difference in the size of your letters here and now it's time to do the punet square so this child is big c big c so they'll be healthy this child is Big C Small C so they'll be carriers but they'll still be healthy same for this one and lastly this child here will have cystic fibrosis so they have a 25% chance of having a child with CF so let's now look at how we inherit our sex and remember this is all to do with chromosomes so women have two x's and men have an X and A Y and that is the pair of chromosomes which dictate your sex so let's literally have a quick look as to why 50% of the population or approximately 50% are male 50% are female so let's start by writing mom and dad as per usual we're going to write phenotype so what do they look like well the mom's obviously female the father is male the Gen type you're going to use the sex chromosomes here so she'll be XX he'll be XY the gamt so obviously every EG will be X sperm we can either be female or male sperm and then if we look at the cross Let's cross the mom up here the dad down here and you see this situation which shows 50% % are XX so they're female 50% are XY so they're male although we know based on that evidence that the man's sperm determines the sax of the child and the chromosomes so the XX or the XY contain lots of genes associated with the development of sex organs you might not know that they have lots of other roles which might not be to do with sex at all and they they code for characteristics which are completely unrelated to sex so the sex chromosomes also carry genes that code for characteristics unrelated to sex and a very famous example of this is color blindness so that's whether you can see in full color or not and because it's carried on the X chromosome so a sex chromosome we say weirdly that color blindness is Sex Link let's look more closely at color blindness as a Sex Link characteristics and a very well known one is red green color blindness which is when you can't tell the difference between the color red and the color green and it's carried on the X chromosome only and when we do our crosses just so you know in order to have color blindness you need to have a small C so if if you're a guy to have color blindness you need to have a x small C the Y you're not going to have a c on it because remember I already told you that it's carried by the X chromosome only as a female to have color blindness you need to have two small C's if you have a big c and a little C then you're just going to be a carrier and if you have two Big C's then you're going to be completely normal so let's do a question to try and make this a bit more straightforward so we're going to cross a carrier woman and normal man so using our normal way of writing out our crosses so we've got a woman and a man the phenotype first of all well we know the woman is a carrier the man is normal the genotype as you look at my crosses up here she needs to have a small C and A Big C in order to be a carrier and he's normal which means he must have a big c attached to the X and remember the Y chromosome doesn't carry any genes for color blindness so we leave that as it is so the gamt the woman's eggs will either be Big C or small C and the man's span will either be Big C or just a y which will obviously code for a male sparm now let's do the cross so this so this first Offspring will be just a normal Offspring the second Offspring will be a carrier of color blindness this male offspring will be normal and this final male offspring will have color blindness so let's write them out 25% of The Offspring will be male and have color blindness and that's due to their combination of alos which is X small c y 25% will be male and they'll be normal because they have X Big C Y 25% will be female and they'll be normal and 25% will be female and they'll be carriers With The Big C Small C co- dominance is when both Ali are expressed in an individual the example here we use is red snapdragons so we've already looked at codominance but they're very interested in the cie exam board in how it works from a blood group point of view so there are four different blood groups they are a b a b and O so you need to learn those you also need to learn the genotypes which represent each blood group and from a codominance point of view remember that we have got to write them in this very specific way which is we choose the base letter and then we have a superscript show showing the Alo for the particular blood group and that will be more clear once I start drawing them out so for a the potential genotypes are i a i a or i a i o for B you're looking at IB IB I IO for ab you're looking at I a and IB and for o you need i o i o just make sure you're clear that that's an or and now let's have a look at an example so you can actually see it in practice so let's look at an example to make it nice and straightforward so we're drawing a genetic diagram to explain the inheritance of blood group in the Smith family Mr Smith has the genotype I a ib and Mr Smith has the genotype IO iio so using my method from before we're going to lay it out as a table so Mr Smith Mrs Smith start with our phenotypes so what blood groups do they have well according to my previous slide I a ib will obviously be blood group AB for Mr Smith Mr Smith has Io Io which means her blood group is O so what are their genotypes well happily that's been given to us in the question that's just i a i b for Mr Smith i o i o for Mrs Smith so the gametes we just need to separate those Al and draw circles around them to show that this is the potential alios for his sperm and her eggs will all be IO now let's do the Panet square and just cross them and then from the previous slide we know what each of the child's phenotype will be so IO I a that's 50% of The Offspring and they'll have blood group a and IO I is the other 50% of potential Offspring and they'll have blood group b so now we need to look at pedigree diagrams and the best way to do this is by showing you an example always use this approach and do notice these are supposed to be really difficult so don't worry too much if you're finding it too much question three Thal hyperia FH is an inherited condition caused by dominant Al that is key people with the condition have high levels of cholesterol in their blood increasing the risk of dying from blocked arteries the diagram shows the pattern of inheritance in several generations of a family with familial hyp Chia so do notice with a pedigree diagram that the squares are always the men in the family you'll know this from the key the circles always represent females and in this case from the key we can see that the gray shaded boxes are suffers of FH whilst the white boxes or circles are non-sufferers so person a is heterozygous for FH use this information to complete the table so let's start by labeling the genotype of f of person a and we are going to use the letter d i mean it doesn't matter what letter you use but I'm going to use the letter D because you can easily see the difference between a capital D and a small D so labeling their genotype this is what they look like so big D small D so what is the question actually asking how many people have the genotype which is homozygous recessive so homozygous recessive homozygous meaning the same case recessive meaning lowercase which is why we're looking for small D small D here homozygous dominant Asus meaning the same dominant meaning that they're both Capital so that's what we're looking for now we're going to work out what the pedigree diagram tells us first of all I'm going to look at all the people without FH so all the people that are either white circles or white squares because they don't have the disease I know therefore that they are small D small D so I can just label all of their genotypes straight away and now we need to count them to work out the number of people with the genotype homozygous recessive once I've done that I can see that it is 11 now we're getting slightly more difficult by looking for the Big D Big D so homozygous dominant so we need to infer things from the pedigree analysis first of all look at woman C so she got her genotype from parents A and B now B is homozygous recessive which means they must have passed on a small D she has the disease which means she must have a big D so this is her genotype e has the same issue but they're a man so they're going to be Big D small D person G inherited a small lowercase Ali or from D they have the disease which is why they're capitalized and the same goes for person J and then looking at no o well they inherited a small D from their mother they have the disease which is why they have a big D so actually looking for people with big D Big D the answer here is zero person G and H have three children all who all of whom have FH what is the probability of g& having three children who all have FH this is a crazy amount of work for one Mark cuz the only way I can see of doing this is to draw a planet Square so we're going to do a planet Square for g&h using my layout I already described so we're looking at the phenotype genotype and gamt from the key we can see the person G has FH H is therefore healthy from the key we've already labeled their genotypes so we can just copy that directly across and then separate these out to see the gamt now just simply do a cross and it's these two here that will have FH now what is 50% as a probability well it's 0.5 and the question asks the probability of all three children having FH so remember when we're talking about probability we have to multiply together our probabilities Pop That your calculator and you'll get a value which is 0.125 n hey did you come in oh you're all soggy why is it why isn't it focusing you're so soggy is it wet out there super soggy so how is variation within a species brought about cuz we know the human race isn't full of billions of people that all look the same that is brought about by a combination of things first of all genetics and secondly environmental factors so two identical twins regardless of the fact they have the same genes if you move them to opposite parts of the world it's very likely they'll have different heights different masses different slightly different skin color and that's due to the environment they experience that could be lots of sun one of them could eat more one of them could do less exercise you're right are you too muddy you're powering aren't you this makes a change let's look at continuous and discontinuous variation now and hopefully you've met these two words in math so you already have a clue a little bit about what they mean now continuous is all to do with having a range of values and it results in a range of phenotypes which fall between two extremes so for example your height so taking people in your year you'll have the shortest person in the year which let's pretend they are 120 cm tall the tallest person might be 2 100 cm tall I don't know if I'm making up silly numbers by the way in the UK for some reason we described height in terms of feet so I'm 5'4 in which is really silly because we use the metric system for everything else whereas discontinuous variation results in limited phenotypes with no intermediate values and we've already met a really good example which is blood groups you're only one type of blood so you could be a you could be B you could be a b or o but you're not a combination of all four the same could be said with something is silly as tongue rolling the general thinking here is that some people can roll their tongues some people can't and you can't kind of do it halfway and be aware that this is all to do with genes which you should know from doing the genetic cross what is the mutation it's a rare random change to the genetic material of an organism so a mutation can be brought about by a number of things things like ionizing radiation exposure to UV light x-ray exposure and various mutagens which are just chemicals which cause mutations and you find those in things like cigarette smoke now the crucial thing with mutations is what they do is they alter the DNA of an organism we've already looked at protein synthesis so if you think about it if you alter the DNA of an organism what that will do is it potentially Alters the sequence in which amino acids are assembled and therefore it can alter the end product so the end protein which is produced proteins are responsible for phenotypes so our physical appearance so mutation can therefore cause an alteration in our phenotypes now not all mutations cause this alteration because sometimes a mutation occurs where the DNA although it is changed it doesn't actually alter the order in which the amino acids are assembled so you end up up with the same protein here it's more of a common sense topic but I do know that some of you struggle with it so I don't want to ignore it right adaptation that is to do with organisms and them having characteristics which mean that they are better suited for a particular environment I'm going to take it from a animal that lives in a cold environment an animal that lives in a hot environment and we're also going to have a look at plants so let's just dive straight into looking at things like polar bears and arctic foxes right what you will find is first of all they have white fur why for camouflage so they blend into the surroundings they have something like a polar be I'm going to actually use that they have large feet why to stop themselves sinking into the snow because if you have larger feet then you have a larger area to spread their weight over it's the same reason why skis work is because you just don't sink in as much right what else do they have they have small ears why because they need a small surface area here because they want to minimize their heat loss to the surroundings as obviously it's very cold and they want to keep warm they'll have a thick layer of fat for insulation they'll have thick fur for the same reason to serve heat if they ask you stuff like oh adaptations for catching prey then you need to talk about sharp teeth for tearing into flesh long legs so they can run fast but they don't usually ask that it's more of adaptations to their environment if we take an animal in a hot country something like a camel that lives in a desert again they have large feet so that they don't sink into the sand they have large ears to increase the surface area to maximize the amount of heat that they can lose because obviously they don't want to overheat under the hot desert sun you'll find that they have Long Island lashes which will prevent sunand getting into their eyes they have thin fur thin layer of fat to minimize the amount of heat that they maintain right lastly let's look at the cactus now the cactus um obviously again lives in the hot environment it stores water in its stem it has spines rather than leaves and what that does is it prevents water loss by transpiration they have shallow extensive Roots um I hope that makes sense to you basically their Roots spread out a very long way meters and meters away from the actual plant and what that means is if it rains then what can happen is that the plant can absorb as much of that water even if it's really far from them very short topic now on Evolution and natural selection so first of all your definition for evolution it states that many organisms which are alive today and many more which are now extinct first evolved from very simple life form that first evolved over 3.2 billion years ago so that's basically saying that Evolution states that we all evolve from small life forms like bacteria which became multicellular which became more and more complicated they became reptiles they became birds and then they became mammals and then we came about so that's really what evolution is stating natural selection links very nicely with this remember this is Charles Darwin's theory now he stated and I do just want you to learn this as a five M answer off by heart he stated that there is variation within a species due to mutation which is what I've just discussed So within a species that is variety this means that some individuals within the species are more likely to survive because they are better adapted because they're surviving they're likely to reproduce so produce Offspring and those Offspring will inherit those favorable genes so before you know it you have many generations that go past and they've all inherited this favorable Gene making them more likely to survive and I'm now going to bring up that perfect answer for you natural selection can be seen pretty much everywhere on Earth including bacteria so we're just going to describe how bacteria may become antibiotic resistant and it does link to Natural Selection so what happens is you have a colony of bacteria you give them an antibiotic and due to mutations some of those bacteria are stronger they are resistant that means they are not killed by the antibiotic so what happen Happ s is all the other bacteria are killed leaving Behind These very strong antibiotic resistant bacteria they soon replicate and before you know you've got a colony of bacteria which is no longer treatable using antibiotics and that's why everyone's so scared about antibiotic resistance and what it means for our future medicine now selective breeding so remember this is when humans use animals or plants with desired characteristics they force them to breed and then they repeat this process process over many generations so before you know it you have animals with desired characteristics so if we're looking at animals let's for example look at the dairy industry so dairy cows clearly a good animal here will produce a lot of milk so at humans to make sure you point out that it's humans they select a dairy cow that produces a high yield of milk they mate her with a bow it's quite hard to determine the bow cuz obviously they don't produce milk but they'll make her with a bow and then her carbs are like to produce more milk the female carves because of their high yield mother then you take those carbs and you keep repeating the process until you have lots of carbs and lots of cows that produce lots of milk and you can do the same with plants so you can selectively breed plants to be a particular color so you pick flowers that are a particular color you force them to cross-pollinate and then before you know you FL a load of plants with your desired characteristics such as petal color ecology now not my favorite topic mainly because it's full of disgusting definitions which all seem to be very similar and all sound the same so let's start by looking at definition of environment that is the total non-biological components of an ecosystem so we're looking at the soil and the water for example the habitat is the place where a specific organism lives Now population be very specific with your key words here this is all the organisms belonging to a particular species which you find within an ecosystem what is the community this is the population of all species found within a particular ecosystem now what is a producer cuz remember producers start all food chains and food webs this is just a plant which photosynthesizes to produce its own food a consumer is an animal which eats other animals or plants what is a decomposer it's an organism which decays dead material and helps to recycle nutrients Define a parasite this is an organism which lives within another organism causing harm to that organism and feeding off of them what is a predator it's an animal which kills and eats another animal gosh these definitions do keep coming what is biodiversity that's the variety of plants and animals found within an ecosystem what are biotic factors these are living factors so these are fact these are living factors which affect organism's lives so it could be other animals competing for food competing for nesting sites bringing disease and pathogens to other organisms abiotic factors are non-living factors which affect organisms such as soil PH temperature of water carbon dioxide availability number of daylight hours Etc looking more closely now at pyramids of numbers and pyramids of biomass so remember a pyramid of numbers simply shows you the number of each organism at each trophic level so trophic level is just the stage in a food food chain so for example a pyramid of numbers could start with grass the grass could be eaten by rabbits so that will be the next here and lastly you'll have foxes but we don't like using pyramids and numbers because often they end up looking a really strange shape and not being pyramidal at all and that can be due to the producer only being one organism such as a tree that will be very small in comparison to the number of sparrows living on it which is why you end up with very funny shaped pyramids so we use pyramids of biomass cuz that actually shows the mass of living material available and therefore the oak tree for example will appear much larger and therefore the pyramid will be the correct shape I'm just going to talk you through a couple of food web questions just so you know how to answer those the diagram shows a food web from a habitat us information in the food web to complete the table the first one has been done for you this has been drawn quite horribly so rather than looking at where the layers are you'll need you're going to need to count the arrows and make sure you remember things about what a producer is and what a primary consumer is so starting with the number of organisms which they've done for us which is annoying because that's the easy question just count how many different organisms there are there R rates so we do agree with them the number of different types of plant you're looking for the producers here so what here is a plant well you can see from the picture even if you don't know what a cattail is but it's a cattail and Marsh Grass so the answer here is two the number of animals so these are the animals which form anything from the primary second secondary tertiary consumer level so the animals therefore are grasshopper Cricket shrew frog snake and Hawk and if you count those up you'll get six number of primary consumers so remember they appear straight after the producers so we've got an arrow leading to the cricket and the grasshopper which is why the answer here is two number of food chains God this is more difficult so food chain one will be Marsh Grass grasshopper shrew Hawk food chain two is the same but includes the snake before the hawk so that will be the second one food chain three is the Cattail Cricket shrew Hawk food chain four will be the same but include the snake and then food chain five will include Cattail Cricket frog snake and Hawk so that was pretty tricky but the answer here is five the plants in this food web make the food for some of the animals to eat give the name used to describe these plants I've already mentioned that a lot that is a producer the hawk catches and eats its prey give the name used to describe the hawk in this food web so I told you earlier in my definitions that something that catches and eats something is a predator a pesticide can be used to kill the grasshoppers in this habitat describe the effect that killing grasshoppers would have on the number of shrews so we need to have a look oh right right so the Grasshoppers are eaten by the shoes so clearly if we reduce the number of grasshoppers the number of shoes will reduce because there is less food for them describe the effect that killing grasshoppers would have on the number of Marsh Grass plants so if we have fewer grasshoppers we can see that they won't be as eating the Marsh Grass as much which means that the Marsh Grass population will increase why is so little energy passed from one organism to another so for example from the producer to the primary consumer so let's take grass the producer and a rabbit as an example remember the rabbit is the primary consumer the issue here is that only part of the grass is digestible much of it passes out of the rabbit as feces some of the grass isn't eaten so the rabbit won't even eat the roots I don't know if that's true but it can be a reason the rabbit moves it keeps itself warm it respires it adjusts I've already mentioned this it poos so these are all ways in which energy is lost within a food chain in fact 90% is lost at each stage of the food chain if they ask you where all that energy originates from remember that is the sun now there's a greater push at the moment for people to become vegetarian and vegan which means eating no animal produce whatsoever and it's not just because it's much kinder to the animal it's not just because it's much kinder to the animal animal it's all to do with energy flow so taking grass and say we feed it to a cow and then the cow is eaten by a human well you know from food chains and the ecology topic that over 90% of energy is lost at each stage of the food chain and so the more stages the more trophic levels you have in a food chain the more energy that will be lost so if you can cut out that c stage and go straight from grass to human I know humans don't eat grass but let's say we pick peas for example then we don't lose 90% of the energy at the stage before most of that energy will go straight from the peas to the human so it's a much better and much more efficient way of eating is if we all became vegetarian and far less energy would be wasted let's do the carbon cycle now I do like this topic if you just learn it as a list of steps it's far easier than learning it as the whole cycle unless you're very artistic kind of pictorial person because I really struggle in that way but I find learning this list of steps works well every time so we're looking at how carbon is cycled in our atmosphere and within living organisms so the place I like to always start is carbon dioxide in the air so what happens to that carbon dioxide in the air well it gets absorbed by green plants in photosynthesis and and it is used to make glucose those green plants then respire because they're living organisms and that releases carbon dioxide back into the atmosphere so here's the first step of CO2 moving in CO2 moving out the plants are eaten by animals and so that carbon that was part of the plants becomes parts of part of the animal body and then the animal respires again releasing carbon dioxide into the atmosphere lastly plants and animals inevitably die and then this is where decomposers come in they break down down that dead material and they respire again releasing carbon dioxide so we can see carbon dioxide went in in the first place with green plants photosynthesizing and then it left via respiration by plants animals and microorganisms do notice that combustion which is burning of fuels and things also releases carbon dioxide into the air now the nitrogen cycle again start in one place and allow your answer to feed in from that so I like to start with nitrates in the soil so remember those nitrates get absorbed by active transport into the root hair cells of the plants nitrates are important in the plant manufactur of proteins so the nitrogen in the air becomes locked up in proteins within the plant the plant is eaten by animals and therefore the nitrogen moves from that plant into the animal and then both the plants and animals die and microorganisms become important again so the the ones you need to know about are nitrifying bacteria and they convert the ammonium within the dead matter from nitrites to nitrates so nitrates have been returned to the soil nitrogen has been returned to the soil do notice there are some really annoying bacteria called denitrify bacteria and what they do is they take nitrates in the soil and convert it back to nitrogen in the air so they're not very popular with Farmers because after all the farmer wants lots of nitrates in the soil they don't want nitrogen being released into the air because there's plenty of nitrogen in the air so that's why D nitr bacteria are particularly frustrating the last thing to notice is nitrogen fixing bacteria which we find on root nodules so small bumps on the roots of leguminous plants legumes are a family of plants which include peas beans and clover so they're super good to plant because they provide a lot of nutrients to the soil the reason being that the root nodules containing nitrogen fixing bacteria they convert nitrogen gas in the air to nitrates so effectively they make the plant its own supply of fertilizers so that's really great because by planting Clover or peas or beans you're basically fertilizing the soil so say the farmer regularly plants wheat as their cash crop they might choose to crop rotate and plant Clover every four years just to add a nice input of nitrates to the soil so now let's look at the factors which affect population growth and we're going to use an example of cows so there's a population of cows and they want to increase their number so what factors would affect how quickly they can increase their numbers well first of all food supply if there's not much grass available then there isn't a lot of food for them to eat so obviously they won't be able to grow and they will starve predation is a Super Key point if there are lions around and the lions eat the cows I'm talking about in Africa by the way I hope you don't think I'm signing really silly with this example then clearly that will limit population growth because you have fewer cows because they have been killed and eaten by the Lions and disease is a very important factor too other cows might introduce pathogens to our original cow population the Lions themselves could introduce pathogens so disease has always been a huge way in which large numbers of people or animals have been killed so for example malaria has been responsible for millions of human deaths the same is true for typhoid cholera tuberculosis Etc however more recently these diseases have been under control when we're concerned with the growth of the human population so over the last 250 years if you have a time on the x axis human population on the Y AIS and we've seen it just go extremely high in just the last 50 years alone and that's s to do with things that we've just discussed so disease medicine has meant that many people who would have previously died are surviving there's improvements in water supply and cleanliness really so not just having more water but making sure it's clean to do with that is sanitation so making sure that our waste is dealt with appropriately and cleanly and we have better food supply however this astronomical increase in human population has huge environmental and social implications it's led to global warming due to the enhanced Greenhouse Effect and that's all due to burning fossil fuels deforestation is going on an awful lot cutting down trees to make more space for animals to feed also to give us building materials for our houses and we're seeing an ever increasing destruction of the ozone layer due to CFCs in our fridges and Aerosoles so these are all impacts of a massive increase in our population the expectation is that the human population will reach an incredible 9 billion people by the end of this century and that is crazy 9 billion people need feeding so how we managed to provide so much food how are farms generating so much food both from an animal and crop point of view so let's look at these different factors so we've improved productivity by using Machinery so in the old days when they used to use ox and plow increasingly modern technology sees us using machinery and what that can actually do is help remove Hedges and if you remove Hedges then you have larger fields and therefore more space to grow crops and animals a large part of productivity to do with growing crops is how fertile the soil is so we can increase the soil's fertility by using fertilizers often NPK ones which remember contain lots of nitrogen phosphorus and potassium which are all needed to encourage healthy root growth prevent yellow spots help build plant proteins Etc coupled with this is the use of pesticides and this includes both insecticides so killing insect pests which feed Upon Our crops as well as herbicides which are weeds effectively that compete for nitrates in the soil for sunlight for water Etc so if we can kill the weeds and we can kill the insects which feed Upon Our crops we can increase the amount of crops we produce and then selective breeding which is all about humans picking animals and plants with desirable characteristics and what that means is the end result is better so from an animal point of view that could include picking cows which are good milkers so produce lots of milk and you keep crossbreeding good milking cows with balls and then eventually you end up with a whole population of cows which produce loads of milk which is obviously great for the farmer from a plant point of view it could mean picking plants which are resistant to disease maybe they're hardier so they don't get get killed by frosts which is a big problem in the colder countries and then the biggest reason for improved efficiency is monoculture so historically Farms were small and mixed so they contained various animals and crops and plants monoculture is the tendency to pick a single crop so let's look at both the advantages and disadvantages of monoculture because with all of these things they're always good and bad points so starting with the good points you can selectively breed plants so what I was just saying you can selectively breed plants with ideal characteristics and you can match them to the type of soil you have to make sure you're maximizing growth and because you know your plant so well you know its exact mineral and water needs so you know to avoid deficiency diseases and then lastly in terms of the Machinery you use if you buy a very specific kind of tractor for a particular type of wheat then you know it can quickly Harvest and we call this specialized harvesting techniques however with the good comes many bad points and as is the way when you grow lots of the same plants close together you increase the chance of disease and a disease that can particularly affect plants is the tobacco mosaic virus and that can easily spread from one plant to the next because you've decreased the biodiversity so you've decreased how many types of plant there are you end up affecting the wildlife as there's less food for Birds less food for butterflies etc etc as you often end up with Fields containing the same type of plant this leads to a loss of genetic variation and remember with this comes problems with natural selection because if the conditions change you find that you don't have a population of plants with enough genetic variations so they're more likely to die out and lastly you see damage to the soil as the minerals get leeched away due to the same plants being present we've already said that we can remove Hedges and create larger fields and that's due to specialized machinery and now we need to look more closely at that and look at the advantages and disadvantage vages of the removal of Hedges and these should be nice and obvious so the most obvious reason you would remove a hedge is to provide more space to grow crops another obvious point is that Hedges provide shade and where they're shade you're going to have less light so less photosynthesis by your crop plant Hedges often provide shelter for animals such as rabbits and rabbits are very destructive forces as far as the farmer is concerned their Burrows destroy land and the rabbits eat the crops again a big no no from the farmer's point of view and then lastly they often need trimming redigging replanting so they need a lot of Labor in order to maintain them disadvantage then so what are the bad things concerned with removing Hedges these are mostly environmental so first of all Hedges act as wind breaks so without Hedges you have no wind breaks which leads to the erosion of soil increasing the leeching of nutrients Hedges also provide a great ecosystem Hedges also provide a great habitat for many animals for many bird species so we lose nesting sites and coupled with that is no shelter for small mammals and then lastly the leaves which fall from the hedges may be cycled into the soil adding nutrients so we have no nutrient cycling if we remove our Hedges so how does using fertilizers increase crop yield well the addition of fertilizes to the soil replaces leeched or lost nitrates and mineral ions from the soil because remember fertilizers are very rich in nitrogen nitrates and those nitrates are used by plants to build proteins what is a pesticide remember it is a chemical which kills pests so anything which feeds off plants will be counted as a pest killing pests obviously reduces their damage to the crop and it also helps to increase crop yield issues though there's lots of issues with using pesticides firstly that they can be very expensive they're persistent which means it takes a while for them to decompose so on you apply them to your soil you've got to be aware that they may hang around for many many years and the problem here is that they can often kill animals which aren't even pests which is really really bad because these are innocent animals getting killed by the pesticides because the pesticide does not discriminate correctly so what happens here is it kills other animals some of these animals get eaten by large animals so we're talking about food chains here and this is called bioaccumulation where the pesticides become stored in these animals and then as this pesticide Works itself up the food chain we call this bi magnification and the famous case study of this is DDT which was used to eradicate malaria and typhoid in the second world war and there are still areas of the world where DDT is killing huge amounts of Flora and FAA and that just means animals and plants deforestation so geographers you ought to know a lot about this remember this is the cutting down of trees why do we DeForest well it provides more land for animal rearing so Farms it provides more land for crops to be grown it provides building materials used in houses and that's everything I'm going to say because I can't think of anything else and then what effect does deforestation have on the environment well it's got some horrendous effects and you can talk quite in depth about these effects firstly by cutting down trees what you're doing is you're releasing an awful lot of carbon dioxide into the air which is obviously going to enhance the Greenhouse Effect and contribute to global warming cutting down trees means that animals habitats are destroyed there's nowhere for them to Nest anymore if we're talking about birds or for animals to hide in the undergrowth if we clear the land you get leeching of nutrients because remember those tree roots hold those nutrients those nitrates in place without the trees you end up with the rain falling on the ground washing away the nutrients into streams and rivers meaning that the whole land remaining is Barren and infertile and tied to this is soil erosion where because of the rain falling you get widespread flooding and landslides and really thinking about it the whole of the water cycle is disturbed because there's less transporation occurring which means because less transporation is occurring due to lack of leaves meaning that less clouds form less rain and you get a whole disruption to the weather found over forested areas let's now look at human impact on the environment and we're going to start with utation which is an effect brought about when farmers use too much fertilizer on their land and when sewage this is disgusting washes into rivers and streams and lakes so do remember fertilizers and seage contain a lot of nitrates so what happens is the plants use those nitrates to build proteins and they grow extremely quickly because they' grown so quickly they end up dying the reason for this is due to lack of light basically they they block all the light for each other and they die because they can't photosynthesize my not one the death of the plants obviously provides lots of food for decomposers and microorganisms so they grow hugely in number because they're feeding on this dead material because they're aerobic respirers they use up all the oxygen in the water courses and this means there's no Oxygen available for aquatic animals and they die and that's how leeching of nutrients of fertilizers and surage can end up with death of all aquatic animals within water courses so remember a non-biodegradable plastic is a big problem and that's because the nonbiodegradability of it means that they can't be broken down using microorganisms because biodegradable means breaking down using microorganisms and these sit on our landfill for hundreds if not thousands of years and you need to look at their issues both on land which is terrestrial and also in our oceans which we call Aquatics so what issues might arise by non-biodegradable Plastics being deposited here so terrestrially believe it or not the Plastics can block water channels meaning that the water can't drain away and sits in the soil which we call water logging and if there's too much water in the soil it actually leads to a decrease in the amount of oxygen available in the soil thus decreasing the soil's fertility meaning that plants can't grow as well both on land and in water they can be consumed by animals and if that ends up in the animal's stomach it won't move anywhere meaning that the animal can't eat any longer so they're liable to starve going into more detail about their deposition in landfill weirdly when Plastics are placed into rubbish heaps so in landfill sites they actually block the passage of oxygen and oxygen is often needed by bacteria to break down waste so it actually inhibits the breakdown of other waste and lastly if we try and get rid of them by burning them you often find with incomplete combustion that soot is produced and if that soot is deposited in the air it can really affect both our and other animals breathing the greenhouse effect now we the greenhouse effect is very famous we're always talking about it because of environmental change do you remember this is due to human activity or we think it's due to human activity so burning of fossil fuels which releases carbon dioxide other greenhouse gases include methane do remember sources of methane so some of that comes from the digestion of B Vine animals such as cows effectively when they farten B that's disgusting they release lots of me rice Patty Fields the microorganisms that are found in rice Patty Fields contribute an awful lot of methane to the atmosphere and remember the other two greenhouse gases you need to know about are water vapor and nitrous oxide so there are four greenhouse gases carbon dioxide methane nitrous oxide and water vapor so what effect does this increas in greenhouse gas have on the environment what you find is that the whole of the Earth's atmosphere heats up and this leads to widespread melting of the polar ice caps this means much more water is added to our seas and oceans and consequently you get a rising sea level this floods low-lying land so towns and cities close to the coast and it will automatically lead to loss of biodiversity because animals have less habitat less places to live in and you can see Extinction of some species we also are seeing a KnockOn effect with extreme weather huge storms typhoons Etc this is all a result of enhanced Greenhouse Effect and Global warm in we now need to look at the conservation topic it's not difficult but it is a matter of Ro learning many things including the definition of a sustainable resource so the crucial thing about a sustainable resource is that it doesn't run out as the name suggests and what that really means is that this re source is produced as rapidly as it is used why is there therefore push to conserve fossil fuels and that's because of the manner in which fossil fuels are made remember they take millions of years to make they come from the bodies of dead sea animals and plants which required a huge amount of pressure and high temperature and because of these unique conditions needed and the time frame they're just going to run out we burn them they will run out and they will not be replaced so crucially they run out and they are non-renewable looking at resources which can be maintained this sounds very strange but clearly resources such as forests where we get wood from which is building material and fish stocks are things which can easily be maintained and controlled fish grow nice and quickly they can be fed very easily as long as it's a high protein diet and you can produce lots of fish in this way more random information you need to know is to do with the names of materials which can be easily reused so used again and again or recycled which means putting them through manufacturing process that enables them to be used again in a different form and such materials include paper glass plastic and metal now we need to look at how our dirty water may be made safe so remember this dirty water if it contains human Wast is known as sewage and that needs to be taken to a treatment plant where it is later recycled and then that water can be used again once it's been cleaned filtered had chlorine added it to it to kill the pathogens why do organisms become extinct which means the permanent loss of a particular species or at least become endangered which is when there's a huge loss in numbers of a particular species well that's due to all sorts of things so one thing that's very hot at the moment in the news is climate change so when we talk about the greenhouse effect being enhanced and we talk about global warming and the melting of polar ice caps remember that causes loss of habitat for polar bears Etc leading to their possible Extinction if they've got nowhere to live other forms of habitat destruction include deforestation which I've already mentioned which is the chopping down trees many animals make their homes within Forest if you cut down the forest there'll be nowhere for them to live and more actively if we hunt animals to kill for either their flash or their Furs that's obviously going to lead to potential extinctions General pollution so as we burn more fossil fuels more acid rain is produced which can damage trees again damaging the habitats of these animals things like lyen very specific species of lyan if the SO2 levels so sulfur dioxide levels are too high certain types of lyan can't grow and lastly if you introduce foreign species and in Britain there's been a real issue with gray squirrels which have come over from America and effectively they've out competed our native red squirrels leading to them becoming an endangered species so we've talked about the miserable side which is to do with why animals become extinct but how can we conserve endangered species so how can we actually improve the numbers of these endangered species first of all by monitoring them by providing protection for them so whether that's giving them nesting sites or pre helping prevent predation we can educate people as to their behavior to prevent them actually leading to the endangerment of these animals something which is more active is a captive breeding program where we capture these endangered animals we give them a nice environment to live in lots of food so they increase the number and then we release them back into the environment and if we're talking about saving plants we have seed banks where we store large numbers of plant seed for growth at a later time another definition you need to be aware of is sustainable development and this is all to do with providing for the needs of the human population without harming the environment how can fish stocks and forests be sustained so we already talked about them as potential sustainable resources but they're not going to sustain themselves how are we actually going to increase the number of trees within our forest increase fish stocks well clearly by restocking so that means adding more fish to the original amount educating people is always a good answer so to prevent over fishing to prevent deforestation and providing quotas which is all to do with controlling the amount that people allowed to either cut down trees or to fish the next thing we need to look at is why species are so so at risk if their population drops why does that ultimately sometimes lead to their Extinction and that's because if you decrease the population clearly you have fewer individuals which means when they breed you have less chance of genetic variation and remember that's crucial for evolution and natural selection to occur so if you have less Chan of genetic variation then it means you're less likely to have Offspring which can survive in adverse conditions and as such you get into breeding and fewer healthy offspring are produced so we're very interested in conservation programs why do we carry out conservation it's pretty obvious it's to prevent Extinction of species like I said not a difficult topic just lots to learn is so that we can protect vulnerable environments so our ecosystems are maintained our nutrients are cycled appropriately within the carbon and nitrogen cycles for example Le and lastly remember we get loads of our pharmaceutical drugs come from our forest from our tropical rainforest if we cut them all down we're not actually going to be able to produce our drugs that we need similarly food and also our fuels because remember biofuels come from cutting down trees so we'll just call that generally resource provision right looking at microorganisms involved in food production so primarily yeast so how is yeast used in bread making don't forget that yeast is a fungus when it's forced to respire an aerobically it breaks down glucose or respires glucose into carbon dioxide and ethanol that carbon dioxide is very important in bread making it creates bubbles which actually helps that bread dough to rise looking at the role of yeast in beer making so the anerobic respiration of yeast remember that produces ethanol I've just told you that and ethanol is an alcohol so that's where the alcohol found in beer originates moving on to fermenters so what is a fermenta well it's a vessel which contains microorganisms which are involved in fermentation reactions so let's describe the structure of a fermentor and how it is optimized to ensure as much of the product is produced as possible so first of all we control the temperature and that's the through a cooling jacket because microorganisms when they respire produce a lot of heat and if too much heat is produced then they can D to the enzymes and actually kill themselves so the cooling jacket has cold water flowing around it which helps to remove excess heat from the fermentor coupled with this you have temperature and pH monitors because obviously you need to determine if the temperature is too high you need to determine if the pH is too Alkali or acidic so it's it's important that we keep watch on the fermenter we also have stirring paddles to mix up the contents and that ensures that the nutrients and heat are evenly distributed you often have an air Inlet not always but sometimes and that's to allow oxygen into the fermentor for any microorganisms which respire aerobically and lastly nutrient Supply because obviously the microorganisms need something to respire genetic engineering now this is quite a complicated topic it is choca block full of key scientific words but if you learn them off by heart you should be fine so remember we genetically engineer things like insulin so insulin is a hormone produced by our pancreas and it's responsible for lowering our blood sugar levels after we've eaten and for type 1 diabetics they find that they don't produce insulin so they really struggle to maintain their blood sugar levels which is where genetic engineering comes in because in the olden days they used to obtain Pig insulin so used to chop into pigs remove the insulin and not only do you have major ethical issues with this but obviously the insulin wasn't particularly fit for purpose because it came from pigs so it was important that we found a way of producing insulin from humans and so that's where genetic engineering came in and when we're talking about genetic engineering we're talking about about using bacterial cells because bacterial cells contain small rings of genetic information called plasmids which we can manipulate so that you can insert the insulin Gene and force the bacteria to produce lots of insulin so let's go into great detail how that is done so we obtain the bacterial cell and we cut open the plasmid using a restriction enzyme which acts as a pair of biological scissors then we use a restriction enzyme to cut the insulin Gene away from the rest of the cell and we insert that insulin gene into that bacterial plasmid using a ligate enzyme and we stick it together and that's why we say it has sticky ends once we've done that we're ready to put the bacterial cell into a fermental and it's been done many many times and then I've already mentioned the fermenta you need to provide it with the optimum conditions to the right temperature the right pH the optimum amounts of oxygen and nutrients Etc and before you know your bacteria has made huge amounts of insulin don't forget a few key words here concerning genetic engineering once that plasmid has a different Gene inserted into it we call it a recombinant plasmid which means it's been recombined so it's been changed and don't forget also that the bacterial cell the plasmid is acting as a vector which means it transports biological material from one place to another we can also genetically modify plants so that they can have desired characteristics this could include being Frost resistant so that stops them dying when Frost hits in Winter it could be to extend their sha life to stop them going off so that they have a longer sh life and are more fit for human consumption after many days you might actually want to make plants resistant to weed killers this sounds really strange because why would you want to make a plant resistant to weed killer but think about it a farmer applies the weed killer by the way the best name for weed killer is herbicide side meaning kill herb meaning to plants so the farmer applies the herbicide he or she wants to kill the weed however some of it will inevitably fall on the plant that they're trying to grow and obviously you don't want that to happen because it will actually kill the plant you're trying to grow so if you can make that crop plant resistant to herbicide then that's great because you apply that herbicide or weed killer it kills the weeds and your actual plant that you're after stays alive and continues to grow you can also genetically mod modified plants so that they can actually have house benefits one of the most famous examples of this is golden rice so when poor countries grow lots of rice unfortunately rice doesn't have a huge amount of nutritional value so what you can do is genetically modify it so that it contains vitamin A and therefore when people eat that Rice they they get a huge amount of vitamin A in their diet and that stops from getting night blindness this is something you should remember from the balanced diet topic of the specification so golden rice is an excellent example where genetic modification has been used really well and then the most strange example of genetic modification is when we talk about tobacco plants and these have been modified so they actually produce hepatitis antigens therefore have a potential vaccine against hepatitis so this is like crazy science but just remember that tobacco plants may be modified to produce hepatitis vaccines so we've already touched on this we've given lots of examples of genetic modification in Plants just to reiterate the advantages and to throw in a few more you can have increased salt tolerance right I hope you found my video helpful Guys these are so difficult to make but I know you guys really like to just sit and watch the whole thing in one so please give me a like like this video if you found it helpful it is a good incentive for me to continue my work and don't forget to sub um back soon with another video bye