this is a summary video for aqa gcc biology paper 2. the video gives you an overview of everything on the paper to allow you to do a last minute cram on the night before the exam if you're taking gcse combined science watch out for the pink headings whenever there's triple science content or use the timestamps in the description below so you know where to skip the first topic in paper two of aqa gcc biology or combined science is the homeostasis and response topic homeostasis is the name we give to the regulation of the conditions inside a cell or whole organism in order to maintain the optimum or best conditions for function in response to changes both internally and externally what this means is that the environment is changing constantly and for a cell to be able to work at its absolute best it must be able to overcome those changes many of these changes are controlled by negative feedback loops negative feedback works when a change in the environment is sensed and a response is created for instance maybe a hormone is released that hormone will be released until the point where that change in the environment has been overcome and then it will stop being released the three named examples of changes you need to be aware of for gcc biology a blood glucose concentration body temperature and water levels homeostasis pathways have three key parts firstly specialized cells called receptors detect a stimulus which is a change in the environment they pass this information to a coordination center like the brain spinal cord or pancreas which is able to decide what to do next the response is then carried out by an effector such as a muscle which may contract or a gland which may release a hormone or enzyme homeostatic responses may be either nervous responses brought about by the nervous system or chemical responses brought about by the endocrine system or a combination of the two put together the endocrine system works by releasing chemical messengers called hormones into the bloodstream and the changes it brings about happen slowly but they tend to last for a long time in contrast to this the nervous system relays information along neurons using electrical impulses it's much more rapid but the responses it brings about last for a shorter amount of time so it's good for an emergency response which doesn't need to carry on happening in the nervous system specialized receptor cells such as the retina cells from the eyes pass information along neurons or nerves as electrical impulses until it reaches the central nervous system the central nervous system or cns is the name we give to the brain and the spinal cord the cns coordinates the response and causes muscles to contract or glands to release a hormone between neurons there are gaps called synapses when an electrical impulse reaches the end of one neuron and needs to cross the synapse a chemical called a neurotransmitter is released this is able to diffuse across the gap and bond to the second neuron triggering another electrical impulse reflex reactions are very fast automatic responses of your body that don't involve the conscious part of your brain that means you don't need to think before you do them and you didn't need to learn how to do them you are born with reflexes they're often linked to keeping your body safe so things like snatching your hand away from a hot object or the pupil of your eye closing down if there's a very bright light you need to be able to describe how the body brings about a reflex reaction but this happens in more or less the same way for every single reflex firstly we start with a stimulus a change in the environment that the body can detect so for instance this could be a hot object that you're touching this is detected by a specialized cell called a receptor so your skin cells contain receptors for pain pressure and change in temperature and they detect that you're touching something hot the receptor generates an electrical impulse and this passes along the sensory neuron to the relay neuron which is in the spinal column this then passes the electrical impulse onto the motor neuron and this will pass it to an effector and the effector will always be a gland or a muscle in this instance it's going to be one of the muscles in my arm which is going to contract to move my hand away from the hot object the first required practical in biology paper 2 is about measuring reaction times to see how they're affected by a factor like caffeine or tiredness a partner drops a ruler which you try to catch and the distance travelled by the ruler before you catch it acts as a surrogate for your reaction time which you can later convert using a conversion table to increase the validity of the experiment you should always use the same hand for the test and the ruler should always be placed in the same position with the zero mark in line with the top of the hand before you start your partner drops the ruler without warning so you don't have an opportunity to anticipate them and give a false reading this experiment could be carried out by the same people before and after drinking a caffeinated drink or by different groups of similar individuals who had taken different levels of caffeine if you're going to take this approach you would need to ensure that the different groups contained participants with the same mix of ages and sexes and also with the same amount of experience with the test this isn't an example of a reflex reaction because it isn't an automatic response and it does involve the conscious part of the brain alternatively we can test people's reaction times using a computer program in which each time an object appears on screen the test subjects need to press a button as fast as they can this allows higher resolution data to be collected and is more likely to give valid data as there's no way the computer can indicate it's about to make an object appear however in order to use this method you need a computer and a program which might not be feasible if you're taking gcc biology or triple science you need to be able to name and describe the function of five brain tissues the main part of the brain is called the cerebrum and the folded outer layer of the cerebrum is the cerebral cortex this controls all the things you kind of think of as making us human our consciousness intelligence memory and language lower down at the back of the brain we have the cerebellum this coordinates muscular control for voluntary movements like running or catching a ball at the front of the brain stem we have the medulla and this is responsible for involuntary movements things you would do even if you couldn't think about them like your heart beating or your lungs breathing behind the bridge of the nose is the pituitary gland this is a master gland and it releases hormones like fsh lh and adh and the hypothalamus amongst other things is the site of the thermoregulatory centre which as the name suggests is responsible for controlling your body temperature scientists have worked out what different regions of the brain do by using mri scanning studying patients with brain damage or electrically stimulating parts of the brain however there are many challenges in studying brain function while patients with brain damage have allowed us to draw many conclusions a lot of people don't have damage to just one isolated area and this makes it difficult to identify which region is responsible for a particular symptom there are ethical concerns with studying someone's brain and also the brain is pretty tricky to access due to the skull many functions of the brain involve the coordination of several different parts and finally when the brain does malfunction there are a huge range of things that could be wrong there's infection tumors trauma or even the biochemistry and the same symptoms can be caused by anything from a bacterial infection to a bump on the head to your body not making enough of a particular hormone and all of these make studying the brain really tricky triple scientists also need to know about the different tissues of the eye the eye is surrounded by a protective layer called the sclera and the front part of this which is transparent is called the cornea as well as playing a role in protection the cornea also focuses about 70 of the light that comes into the eye this light then passes through a small hole called the pupil which is surrounded by a muscular ring called the iris the iris can contract and relax in order to control the shape and size of the pupil behind the pupil is the lens and this is going to finish focusing the light hopefully onto the retina the size and shape of the lens is changed by the suspensory ligaments and the ciliary muscles when light reaches the retina it's detected by two types of light sensitive cells rod cells which detect light intensity and cone cells which detect light color this information is then passed to the optic nerve the iris adjusts the size of the pupil in response to light intensity in dim light conditions the radial muscles contract and the circular muscles relax causing the pupil to be large and lots of light to enter in contrast in bright light the radial muscles relax and the circular muscles contract making the pupil much smaller and preventing light from getting in and damaging the retina the eye also adjusts in a process called accommodation in order to focus light that arrives from near and far objects when light arrives from a far object the lens must be tall and thin so that the light is refracted less this is achieved by relaxing the ciliary muscles and tightening the suspensory ligaments when light arrives from a nearer object the lens needs to be short and fat so that light is refracted more to achieve this the ciliary muscles are contracted and the suspensory ligaments are relaxed myopic patients experience blurry vision because the light entering their eyes focuses before it reaches the retina this can be treated with a concave lens which causes the rays to diverge long-sighted patients find that the light focuses behind the retina and so this is treated with a convex lens which makes the light focus faster also both of these problems can be treated using laser eye surgery and lens replacement human body temperature is controlled by the thermoregulatory center or trc in the hypothalamus of the brain it contains receptors that are sensitive to the temperature of the blood and it also receives information from the skin sent in the form of nervous impulses when the body temperature rises too high this can be counteracted by widening the arterials close to the surface of the skin so that more blood passes through them this is a process called vasodilation as the warm blood passes through the arterioles more energy can be lost to the environment additionally it's possible for the body to start sweating more the sweat absorbs energy from the skin and evaporates and this cools the body down it's important that you understand that the body is sweating constantly but when you're hotter you sweat more when the body is too cold vasodilation is reversed in a process called vasoconstriction the arterioles constrict and therefore less blood can flow close to the skin additionally the muscle cells may start contracting when you shiver and this also releases heat energy and also hairs on the skin become erect in order to trap warm air the second system involved in homeostasis is the endocrine system which is the system of hormones hormones are chemical messengers carried in the blood until they reach a target organ where they bind and act there are six specific endocrine glands that you need to know the locations of in the brain just behind the bridge of the nose is the pituitary gland then your pancreas is part of your digestive system it's the small leaf-shaped organ that also produces a number of the digestive enzymes your thyroid is in the neck by the adam's apple and your adrenal glands are sat on top of the kidneys and then depending on your sex you have either ovaries or testes the pituitary gland is called the mastogland because it's a gland but it acts on other glands so the pituitary gland releases some hormones and they move through the blood to the other glands and act on them and then those other glands produce further hormones so we can have a kind of cascade effect your thyroid gland produces a hormone called thyroxine and this is responsible for your basal metabolic rate that underlying metabolic rate that you have all the time regardless of how much exercise you're doing or what you're eating and it's really important for growth and development so people that have an underactive thyroid gland often have difficulties with their growth thyroxine is controlled by a negative feedback loop so basically what this means is that the thyroid gland will produce it and then monitor until there's too much in the blood and at that point it will stop producing it and wait for the levels to come back down your adrenal glands make adrenaline which is important for times of fear or stress because it manages that fight or flight response it increases the heart rate and this is important because it means that your muscles and brain can get more oxygen and more glucose to do more respiration so that they have more energy it's really important that your blood glucose levels remain more or less constant both because you need a regular supply of energy and also because if they fluctuate too much it can cause damage to your cells your pancreas is responsible for both monitoring and controlling the level of sugar in the blood and it does this by using two hormones called insulin and glucagon when the blood glucose level rises too high the pancreas makes insulin and this causes the permeability of your cells to increase so that sugar moves into the cells particularly in the liver and the muscles and here that excess glucose is converted into a large storage polymer called glycogen if you're taking the higher tier then you also need to know about glucagon which is the hormone that works in reverse so when blood glucose levels get too low the pancreas makes glucagon and glycogen is turned back into glucose we can see this in action here blood glucose level rises so the pancreas is stimulated and it makes insulin which it secretes into the bloodstream this causes glucose to be taken up from the blood and stored in the liver and muscles so that blood glucose level falls then if you're taking higher tier you need to know that the pancreas will be stimulated again but this time it produces a different hormone it makes glucagon and this causes the liver to release glucose so the blood glucose level goes back up again linked to blood glucose levels are type 1 and type 2 diabetes type 1 diabetes is often diagnosed in much younger patients because it isn't caused by a lifestyle risk factor it has a genetic component and it often runs in families if you have type 1 diabetes then your pancreas stops making enough insulin and this means your blood glucose levels can go scarily high in order to be treated you have to take injections of insulin and without these you could even die it's diagnosed with the four t's because your blood sugar levels get so high the only way to get rid of that blood sugar is to urinate it out so you need the toilet constantly and also because you're urinating so much you need to drink constantly so you're thirsty all the time because so much of the sugar that should be going into your muscles as glycogen is being wasted and urinated out you're tired all the time because you don't have enough energy and you often lose weight as well in type 2 diabetes the pancreas is still producing enough insulin but because the insulin levels have been so high for so long the body cells stop responding type 2 diabetes is often associated with obesity which we can call a risk factor and in order to treat it we use a carbohydrate control diet and an exercise regime it's really important that the level of water in the blood is controlled because if it isn't then the red blood cells could either shrivel up or burst this process is called osmoregulation we naturally take in water when we eat and drink but then we lose some in an uncontrolled way by breathing out the waste products of respiration and by sweating and we lose some more in a much more controlled way from our kidneys in order for our bodies to remain healthy the amount of water that we take in and lose must be balanced each day if you're taking triple science then you need to link water control together with removing nitrogen-based waste as we digest protein this creates amino acids and these can't be stored in the body so they need to be excreted in the liver the amino acids are deaminated and this makes a toxic waste product called ammonia ammonia is quickly converted to urea and this is then filtered out of the blood by the kidneys unfiltered blood in the renal capillary consists of water glucose sultan's urea and also some really large molecules made of protein and also some blood cells under high pressure the water glucose sultans and urea are all able to pass into the kidney but the proteins and blood cells are far too large and they continue into the renal vein instead next the kidney undergoes a process called selective reabsorption we want to get back some of the water and some of the salt rather than having it pass into the urine and of course we want to rescue as much of the glucose as possible because that is a valuable source of energy but the urea all needs to be got rid of carefully controlled amounts of water and salt as well as as much of the glucose as possible pass back into the blood in a process called selective reabsorption the urea mixes with the remaining water and travels down the ureter to the bladder to make urine the precise amount of water reabsorbed is controlled by a hormone called antidiuretic hormone or adh which is made by the pituitary gland in the brain this increases the permeability of the kidney tubules and causes more water to be reabsorbed a person suffering from kidney failure can be treated using either dialysis or a kidney transplant in a dialysis machine a person's blood flows alongside a partially permeable membrane with dialysis fluid on the other side the dialysis fluid contains the same concentration of useful substances like salt and also potentially a slightly higher concentration of glucose this prevents glucose and salt from being leached out of the blood during dialysis however the dialysis fluid doesn't contain any urea so urea will gradually diffuse across the partially permeable membrane into the dialysis fluid where it can then be removed it's not necessary for the dialysis fluid to contain protein because the protein molecules are too large to move through the membrane some patients are able to receive a kidney transplant and this can either come from a live donor who's chosen to give up one of their two kidneys or from someone who's recently died maybe in a car accident and their kidneys were still functioning normally the new kidney is surgically connected near to the bladder and the old kidneys are left in their original position one big advantage of transplants over dialysis is that the kidney is able to work continuously so there isn't a requirement to visit the hospital multiple times a week for dialysis however there's a major risk of rejection whether white blood cells will attack the new kidney in order to try to avoid this before the transplant patients must undergo tissue typing where we try to match a donor and a patient so that their cells have the most similar possible antigens and their white blood cells won't attack the new organ transplant patients also take drugs called immunosuppressant drugs in order to make their white blood cells work less efficiently but this does make them more susceptible to other diseases during puberty the levels of reproductive hormones like estrogen and testosterone begin to rise and this causes the development of secondary sexual characteristics like breast growth and facial hair growth in females the main reproductive hormone is estrogen which is produced in the ovaries and in males is the testosterone which is produced in the testes and stimulates sperm production the menstrual cycle is controlled by four different reproductive hormones firstly follicle stimulating hormone or fsh is produced by the pituitary gland in the brain and this causes an egg in the ovary to mature then luteinizing hormone or lh stimulates ovulation where the egg is actually released lh is also produced by the pituitary gland estrogen and progesterone are both involved in maintaining the uterus lining and these are produced in the ovaries at the start of the menstrual cycle as progesterone levels fall the lining of the uterus is shed follicle stimulating hormone causes an egg to mature and also stimulates the production of estrogen this causes the uterus lining to regrow ready for a fertilized egg to implant estrogen inhibits fsh and it promotes lh and when lh is produced this leads to ovulation high progesterone levels maintain the uterus lining and if pregnancy occurs progesterone levels will remain high so that the uterus lining remains intact contraceptives can be split into hormonal methods which use progesterone and estrogen or synthetic versions of those hormones in order to inhibit the release of fsh and lh or non-hormonal methods which work by preventing the sperm from reaching the egg in choosing a method of contraception you need to consider the reliability so how likely are you to get pregnant the availability would you be able to get that method of contraception when you wanted it any health implications for instance estrogen-based methods increase the risk of blood clots and therefore if you already have a clotting disorder a doctor may be unwilling to prescribe you an estrogen-based method of contraception any ethical or religious views and finally the economics how expensive is that method of contraception if you're taking higher tier you also need to be able to describe the use of sex hormones in fertility treatments fertility drugs contain follicle stimulating hormone and luteinizing hormone which together stimulate egg maturation and ovulation some women may be able to conceive naturally after receiving a dose of fertility drug if this is not successful then the woman may undergo in vitro fertilization she takes the same fertility drug and then the eggs are harvested and they're fertilized in a laboratory instead after they develop into embryos several embryos may then be implanted back into her uterus although fertility treatment does give women with fertility problems an opportunity to have a baby it's stressful both emotionally and physically and the success rates are low as a result of this we tend to implant multiple embryos at the same time but this means that if multiple embryos implant successfully it can lead to multiple births and having twins or triplets is much more risky than a single birth plants need to be able to respond to stimuli in their environment and if you're taking the triple science exams you should be able to describe how this is achieved unlike animals plants don't have a nervous system or a bloodstream and the chemicals they produce do not move around the organism like animal hormones instead they tend to act quite locally plants use hormones to coordinate their growth in response to light which is called phototropism and gravity which is called geotropism the hormone that helps with this is called auxin in the shoots auxin promotes cell elongation and growth and in the roots this is inhibited when a shoot first germinates the distribution of auxin is more or less even but when the shoot is exposed to light the auxin on the light side breaks down or moves away from the light so there's more on the shaded side this side of the shoot will grow faster and the cells will elongate this causes the shoot to bend towards the light in what's called positive phototropism in roots the same process causes the root tip to grow away from the light which is negative phototropism in the shoots and the roots auxin collects on the lower side of the tip in response to gravity since auxin slows root growth this means that the lower side of the root will grow less and the root will turn towards the center of the earth this is positive geotropism in shoots auxin promotes growth and so this causes the shoot to grow away from gravity which is negative geotropism gibberellins are another important plant hormone used to promote seed germination and ethene is a third example of a plant hormone which is produced by ripening fruit it's the reason that if you put ripe bananas next to other fruit then they ripen too often fruit that's going to be sold in supermarkets is picked before it's ripe so that it has a harder skin and it's less likely to be damaged when it's being transported and then when it reaches its final location it's sprayed with ethene to make it ripen for the triple science required practical you should have investigated the impact of either light or gravity on some newly germinated seedlings in order to do this you would probably have grown seedlings in two identical petri dishes and placed maybe one of them on a brightly lit windowsill and the other in a dark cupboard or put them at different angles the independent variable would be the fact that you're changing in this instance probably the light intensity the dependent variable would be the thing that you're observing so probably how tall the seedlings grew or whether they grew towards one side or the other it's important to control variables such as using the same species of seed usually mustard or cress sowing them all on the same day making sure that there are the same number of seedlings in each petri dish and giving them the same amount of water and either a nutrient medium or cotton wool plant hormones also have several uses in gardening and in farming auxin can be used as a weed killer by promoting uncontrolled growth so a weed uses up all its resources and then dies it can also be included in rooting powders and tissue cultures ethene as we've said can be used to make fruit ripen at exactly the right time and gibberellins can be used to end seed dormancy promote flowering or increase fruit size the second unit in paper two of gcc biology is inheritance variation and evolution and the first thing we need to know about is the different types of reproduction in sexual reproduction there are gametes or sex cells these are formed by meiosis the gametes in animals are sperm and egg cells and in plants they are pollen and egg cells the nuclei from the gametes fuse in a process called fertilization this will make genetically unique offspring even if both gametes come from the same parent don't forget some organisms are able to sell fertilize and reproduce sexually with themselves but this is not the same thing as asexual reproduction because it still involves gametes and fertilization the offspring will be different to each other and different to the parents because the alleles will be combined in different ways asexual reproduction by producing runners like a strawberry plant or spores like many fungi does not involve gametes or fertilization and it produces clones which are genetically identical to each other and their parents if you're taking triple science then you should be able to evaluate the advantages and disadvantages of each method of reproduction as many organisms can do both strawberry plants can produce flowers for sexual reproduction but also make clones asexually using runners daffodils can reproduce asexually with their bulbs as well as sexually with their flowers and malarial parasites reproduce asexually in the human host but sexually inside the mosquito fungi can also reproduce asexually using spores as well as sexually the reason for being able to do both is that each method does have its advantages and situations where it's better to do sexual reproduction introduces variation and this is good if uncertainty lies ahead if you produce four different offspring it's likely that one of them will survive whatever the world throws at it this also allows for faster evolution because conditions will favor a particular set of characteristics on the other hand if your environment isn't changing and you're already successful in it then it's likely that clones of you would also thrive so asexual reproduction could be better this is why aphids reproduce asexually throughout the summer while the weather isn't really changing but revert to sexual reproduction to produce offspring for the next year asexual reproduction also doesn't require a mate which allows you to colonize new habitats and the process itself is often faster too so it's more time efficient you need to know about two types of cell division for paper one we talked about mitosis which happens in all body cells and allows them to make more body cells for growth or for repair it starts with dna doubling and then the cell divides once so there are two diploid cells made these cells are identical to each other and identical to the cell they were made from meiosis we only talk about in paper two and it happens in the reproductive organs so the testicles and the ovaries it makes sex cells also called gametes so that's pollen egg cells and sperm cells depending on whether we're talking about plants or animals the dna also doubles at the start just like it does in mitosis but then the cells divide twice so rather than producing diploid cells with the same amount of dna as the parent cell it produces haploid cells and four of these the cells are different to each other and also different to the original cell because they have half the amount of dna that the cell started with more so than probably any other unit biology unit 6 contains a lot of vocabulary that you really need to know the definitions for we routinely see in exams that students understand the biology but because they're not using the right term or they're not able to define it properly they're not getting the credit so i would really recommend that you have each one of these on a flash card and just memorize it a gene is a length of dna that codes for a particular combination of amino acids and those amino acids all in a chain go together to make a protein the different variants of that gene are called alleles so for instance you could have a gene for hair color and then there's a blonde hair allele and a brown hair allele the actual alleles that you have your dna sequence is called your genotype and then the phenotype is the expressed characteristics what can we actually see or observe that happens because you have those particular alleles if you have two alleles that are the same as each other then you're homozygous whereas hetero means different so heterozygous individuals have two different alleles and then finally recessive and dominant are the number one terms that students understand but can't define so an allele is recessive if the characteristic that it codes for will only be expressed in a homozygote whereas an allele is dominant if the characteristic that it codes for will be expressed even in the heterozygote if you think about the hair colour example if you have one brown hair allele then it doesn't matter if the other one is blonde that brown hair allele will still show up it will still be expressed whereas the blonde hair allele will only be expressed if it's accompanied by another blonde hair allele in a homozygote the genetic material of a eukaryotic cell like a human cell is contained in the nucleus the genetic information is made out of a chemical called deoxyribonucleic acid or dna for short dna is an incredibly long molecule made of two connected chains that form a double helix sort of like a spiral staircase made out of a ladder these long pieces of dna get wound up into tiny structures called chromosomes when we talk about the genome of an organism we mean the entire genetic material of our organism the sequence of every single gene and also the intermediate pieces of dna that don't code for proteins the whole human genome has now been sequenced and this is going to have real importance for medicine in the future the human genome project was a massive undertaking by scientists in many different countries it ran from 1986 although it officially launched in 1990 up until its completion in 2003 the scientists sequenced 3 billion bases of dna from 100 anonymous volunteers to allow them to search for genes linked to different types of disease understand and treat inherited disorders and also to trace human migration patterns from the past if you're taking the triple science exams then you also need a little bit more detail about the structure of dna dna is a polymer a very long chain of repeating units called monomers and the monomer that dna is made out of is called a nucleotide and it has three parts firstly we have a pentose sugar which just means a sugar with five carbon atoms in it called deoxyribose attached to each deoxyribose molecule are two things a phosphate group and a base the phosphate group and the sugar together make a sugar phosphate backbone and that's what forms the sides of the ladder of dna the nitrogenous bases are responsible for giving the actual code of the dna there are four different nitrogenous bases adenine cytosine guanine and thymine and they always pair together in the same way adenine always pairs with thymine and cytosine always pairs with guanine this means if the dna is damaged it can be repaired by referring to the other strand the dna bases are read in groups of three and these are called triplet codons so each section of three bases gives you the code for one particular amino acid proteins are synthesized using dna as a recipe which tells the cell what order the amino acids should be put in there are two steps transcription and translation if you imagine an explorer finding a new piece of language carved on the wall of a cave they would need to first write it down and copy it out that's the transcription and then they would need to take it away and work out what it said that's the translation in transcription a copy is made of the gene that's going to be expressed this is made in the form of a molecule called mrna or messenger rna rna is another nucleic acid and it's quite similar to dna but mrna is only single stranded it uses a slightly different sugar called ribose rather than deoxyribose and also it uses slightly different bases but it's used to make a copy of the dna which is locked in the nucleus which can then leave the nucleus and go out into the cytoplasm in the cytoplasm it interacts with ribosomes and the ribosomes are going to read the bases in sequences of three and we call those a triplet codon so you read three bases and that tells you to recruit a particular amino acid this is done using a molecule called transfer rna or trna changes to the dna called mutation are happening constantly either spontaneously as cells divide and make copying errors or as a result of exposure to mutagens like uv light or carcinogens in cigarettes many mutations have no impact at all on the proteins our bodies make either because they happen in a non-coding region which doesn't actually contain a gene or because there's redundancy in the codons used what this means is because there are 64 possible combinations of three bases but then there are only 20 amino acids that our bodies need to make sometimes there's more than one code for a particular amino acid for instance agg and aga both code for the amino acid arginine so if the third letter is changed from a g to an a it won't actually change the protein at all if the protein is changed this can have a real impact for instance an active site of an enzyme is a really precise shape to allow it to interact with a substrate and if that's changed at all then the enzyme might not be functional anymore some mutations may not affect the shape of a protein but they may affect how much of it there is because the mutation may have occurred in a region that is responsible for controlling how much of that protein is made for genetics it's quite likely that you're going to be asked to either draw from scratch or fill in the gaps in a genetic diagram like these ones often called a punnett square there are two genetic disorders that you need to know about so we're going to use these to work through these examples but you could also be told about a new genetic disorder that you haven't heard of and ask to use that information to fill in another punnett square cystic fibrosis is a disorder that affects the membranes and it causes them to produce lots of sticky mucus so this can lead to difficulty breathing because of the membranes in the lungs and also problems with the digestive system because of the membranes in the small intestine in filling in this genetic diagram we're going to pick one letter to use for the gene and then we're going to use a capital letter to show the dominant allele and a lowercase letter to show the recessive allele it's normal to use f for cystic fibrosis but it doesn't matter if you're using another letter however i would recommend that you try to pick a letter that has a distinct difference between the capital and the lowercase because if your examiner can't tell whether you're saying something is dominant or recessive then you won't get credit for it in this question we've been asked to draw a punnett square that shows the likelihood of two heterozygous parents having a child with cystic fibrosis the letters at the top and down the left hand side show you the alleles are carried in their gametes and then in the four squares we show the genotypes of the offspring you can see that we've just taken the alleles from the gametes and matched them up in this instance because cystic fibrosis is a recessive disorder it's only the offspring who has two recessive alleles who inherits the disorder so between these two heterozygous parents there is a one in four chance that they have a baby with cystic fibrosis the other genetic disorder that you need to know about is polydactyly and this is a disorder that causes developing babies to grow extra fingers and extra toes before they're born it's caused by a dominant allele and that means you only need to inherit that allele from one of your parents in order to be born with the disease in this question we've been asked to draw a genetic diagram showing the likelihood of one parent who has the disease and is heterozygous having babies with another parent who doesn't have the disease having a child that also has polydactyly as you can see here the chances are 50 in humans sex is determined by one pair of chromosomes out of the 23 total pairs and these are called the x and the y chromosomes if you are looking at a carrier type under a really powerful microscope then an x chromosome is a similar size to the rest of the chromosomes but the y chromosome is absolutely tiny over thousands of years it shrunk and shrunk and shrunk until pretty much all it codes for is sex determination in the vast majority of cases human males have x y chromosomes and females have xx chromosomes this means that the sex of a baby is down entirely to the chromosomes it inherits from its father's sperm the woman's egg always contributes an x chromosome this means that overall there's a 50 chance of a baby being born as male and 50 female embryo screening is a technique used by doctors with prospective parents who are worried that their baby is going to have a particular genetic disease that runs in their family it can be used to look at a very early stage of pregnancy often when the embryo is formed in a petri dish as part of ivf to see whether that embryo has this particular genetic disorder that the parents are worried about the point of doing this is to try to make sure that we're not bringing babies into the world that are going to really suffer from a disease also often the cost of treating these disorders and trying to keep a baby with the disorder alive can be really high so there's an economic argument as well often when this is done the parents will undergo ivf and produce a lot of embryos and the leftover embryos can be donated for scientific research or sometimes for treatment for instance where stem cells are needed there are some downsides though obviously there are some big ethical issues if you've got a number of embryos and some have the disorder then they're going to be rejected and ultimately destroyed and some people are okay with that because we're just talking about a tiny bundle of cells that can't feel pain but some people believe that life begins at conception and would not be okay with this there's the potential for people to have designer babies so some people are worried that parents would want to screen their babies for say blue eyes at present that's not possible in the uk you can only even screen for sex if your family has a disease that's really closely linked to the sex chromosomes so say it might be easier to identify male embryos and discard them than actually screen for the particular gene on the sex chromosome causing a disease you can't just use embryo screening to identify male children because you really want a son there's also an implication here that the babies that would have the genetic disease are undesirable and there's a risk that by using embryo screening we're kind of saying that people who are born with that disorder are somehow less good and that could lead to prejudice also the embryo can't consent because they're just a ball of cells so that's another ethical issue too embryo screening tends to be quite an expensive process and also if you're doing the version of this where you screen the baby while it's inside the mother's uterus rather than while it's still in a petri dish then there's a risk of miscarriage and also there's a risk of false positives so you could tell a woman that the baby she's carrying has a genetic disease and she might decide to terminate that pregnancy but there's actually a tiny but non-zero chance that you're wrong and she's now terminated a healthy pregnancy instead this is a prime example of an area where you might be given an evaluate question and you should know that in gcc science anywhere that you see the word evaluate you need to compare and also write a conclusion so for instance thinking about the two genetic disorders we've looked at polydactyly and cystic fibrosis you might be asked to evaluate whether it would be appropriate to use embryo screening for either one of those diseases and so you might want to think about things like well how much suffering is a child actually going to go through cystic fibrosis is a life-limiting illness it's not necessarily going to shorten your lifespan anymore because we've got a lot better at treating it but it is going to involve some pain and some hardship and needing to take certain drugs whereas polydactyly may not be a huge amount of fun and maybe you might get bullied for having some extra fingers but amputation is always an option and it's not really going to affect your quality of life so you might want to say that in the case of embryo screening parents might think about using it although they might choose not to for all the other reasons we've identified but for polydactyly it might be less appropriate because at the end of the day you're still going to have a healthy child they just might have some extra fingers and toes in order for you to understand evolution and adaptation it's important that you first understand the necessity of variation if you have an army of clones then it's not possible for any evolution to occur because there's nothing for selection pressure to act on variation is the differences between individuals of the same species and it can either be genetic environmental or a combination of the two genetic variation comes about because of mutation which is happening all the time both spontaneously every time your cells divide and also because of mutagens like uv light or carcinogenic chemicals most mutation has no effect on the phenotype but a small number of mutations do and most of those are deleterious which means they have a bad effect in gcc biology the term evolution refers to a change in inherited characteristics over time as a result of natural selection and it may result in the formation of a new species if two populations of one species end up becoming so different to each other because of evolution that they're no longer able to interbreed and produce fertile offspring we now believe that all species evolved from simple life forms that first developed more than three billion years ago natural selection begins with changes in the genome brought about either by mutation or by sexual reproduction leading to novel combinations of alleles this means that individuals of a particular species will show variation for a particular characteristic a selection pressure can then act on this this might be the likelihood of being killed by a predator or access to a particular food source the individuals that are best adapted to that environment are most likely to survive and crucially to breed successfully in doing so they're able to pass on their alleles and therefore the next generation of that species will have more of that particular successful characteristic for instance pre-industrial revolution white peppered moths were well camouflaged on silver birch trees and on the rare occasion the mutation led a black moth to be born it was quickly seen and eaten by a predator however when the factories started producing lots of black smoke and the trees gradually became darker the darker moths had an advantage they were able to survive for longer because they were camouflaged and to breed and pass on their alleles within just a few years there were far more darker moths because the dark moths had been able to have more babies however when the industrial revolution finished and the trees reverted to their original colour so did the moths another really good example of evolution by natural selection is the evolution of antibiotic resistant bacteria bacteria are able to evolve faster because they have short generation times and a higher rate of mutation and additionally because they only have one copy of each gene any mutation is much more likely to affect their phenotype antibiotics are molecules made by fungi or synthetically in a lab which can be used as drugs to kill bacteria although not viruses normal bacteria are susceptible to antibiotics which means that if you take the drug then quickly all the bacteria are killed however some bacteria can mutate and become resistant and this makes them much harder to kill you start taking the drug the susceptible bacteria will quickly die but the resistant bacteria are able to live on for a little bit longer at this stage lots of people think that they're better and they stop taking the antibiotic this just means that now there's less competition from the susceptible bacteria the resistant bacteria can reproduce freely and make the most of the resources but if the patient had carried on taking the antibiotics then eventually all of the bacteria would have been killed to prevent this from happening it's important to use antibiotics as little as possible you should never prescribe them for a viral infection because antibiotics don't kill viruses and if somebody has a mild infection that they're going to get over on their own then you shouldn't really give them to them either if a doctor prescribes you a seven day course of antibiotics it's really important that you take all seven days worth of drugs and don't just give up after four or five because you feel better we tend to try to avoid using the same antibiotics for humans and for animals and where possible we use narrow spectrum antibiotics which only work on a few specific species of bacteria maintaining hygiene with regular hand washing is also important and when someone does have an infection with an antibiotic resistant bacteria for instance mrsa then we try to keep them in isolation to prevent that infection from spreading selective breeding is the process of breeding plants or animals for particular desirable genetic characteristics for instance we might want to breed cows that produce more milk or plants that have particularly large or beautiful flowers we start with a mixed population that shows variation and identify the individuals that have the desired characteristic we breed these together and then from the offspring select the best individuals we then breed those together and repeat this for many generations until the entire population showed the desirable characteristic genetic engineering is an even faster and more efficient way to develop a population that all have a particular characteristic rather than taking two parents that have the characteristic and breeding them together and hoping that the offspring will have it we can take the gene and directly insert it into an individual this also means it's possible to transfer genes from a completely different species plant crops have been genetically engineered to produce bigger fruits or be resistant to diseases and bacteria have been genetically engineered to produce human insulin to treat diabetes if you're taking the higher tier of gcse combined science or gcse biology then you need to be able to describe the process firstly restriction enzymes are used to isolate the required gene from the organism where it's originally found so in this instance restriction enzymes are used to cut out the human insulin gene from the human genome the gene is then inserted into a vector such as a bacterial plasmid and this can then be inserted directly into the cells the genes are transferred at an early stage of development so that the whole organism develops with the desired characteristics despite being very expensive and quite hard to do gm technology has a major advantage over selective breeding in that it's extremely precise because we're only transferring specific genes that we already know the function of however it does have some drawbacks one major use of gm is to make crops resistant to herbicides chemicals that kill plants this means that rather than carefully spraying herbicide just on the weeds around your crops you can spray it onto the entire field without killing your crop however if the crop goes on to breed with a weed to produce a hybrid these new weeds could be resistant to the herbicide too another way gm is used is to make crops that contain cry protein which is toxic to insects that try to eat the plant but harmless for humans this prevents you needing to spray insecticide on the crops to stop things from eating them however some people are concerned that this could still have an impact on other insects like pollinators because gm technology is so new there's been limited research into its impact on human health which makes some people nervous about eating gm crops even though we know the function of the small number of genes have been transferred modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders the next part of triple science content is all about cloning which is used to produce a population of genetically identical individuals now just to be clear because a lot of people seem to be confused by this cloning doesn't involve genetic modification and it doesn't kill any of the organisms involved it just allows us to produce a large number of identical organisms there are four techniques you need to know about cuttings and tissue culture are used with plants and then embryo transplants in adult cell cloning or fusion cloning are used with animals when you take a cutting you remove a small section of the plant that involves some meristem cells or stem cells and then use rooting powder which contains plant hormones to make those stem cells produce roots and these can then be planted out tissue culture works in a similar way but we have an even smaller amount of tissue often just a few cells and they're grown on a nutrient agar rather than in soil embryo splitting often confuses students because it's very much the odd one out in terms of cloning because it does involve sexual reproduction and it doesn't produce offspring that are identical to the parents they're just identical to each other so embryo splitting starts with sexual reproduction between two parents and they produce an embryo and as that embryo begins to divide it's split apart basically artificially making a whole bunch of twins each one of those twins is then put into a host mother or a surrogate mother who will carry them to term so what we're left with is one herd who are all identical to each other but all slightly different to their parents because they've been made through normal sexual reproduction adult cell cloning is the type of cloning that was used to clone dolly the sheep if i want to clone my white sheep up here the first thing i do is remove one of its body cells it's somatic cells then i take an egg cell usually from a second animal and i remove the nucleus from that egg cell i put in instead the nucleus from the body cell from my white sheep then i use an electric shock to start that embryo dividing and then i can put it within a host mother or a surrogate mother who will carry it to term when she gives birth the clone that she gives birth to is identical to my white sheep that i started with natural historian charles darwin published his theory of natural selection in 1859 in a short book called on the origin of species his ideas were seen as controversial because they challenged creationism and he lacked the evidence to back up his theory and also because the mechanism of inheritance i.e genes wasn't discovered for another 50 years or so this led to cartoons mocking him like this one in which his ideas were simplified and critics said he was claiming that humans were no different to apes jean-baptiste lamarck was another scientist who proposed that changes that occur in an organism's lifetime can be inherited but we now know that this is not usually true another scientist who wrote about natural selection and collaborated with darwin was alfred wallace he particularly wrote a lot about speciation and he realized that most speciation happened when there was some kind of geographical barrier splitting one population into two for instance a new river might form and this might lead to two populations on either side of the river that couldn't interact and couldn't mate with each other over time as different mutations appeared in the different populations and they evolved separately from each other they might become so different that they could no longer interbreed and at this point we would have two new species in the mid-1800s an austrian monk called gregor mendel carried out breeding experiments on pea plants and he realized that whatever was being passed on wasn't blending together it could be separated back out and so it was possible for traits to skip a generation he called the material being passed on units later in the 19th century chromosomes were observed during cell division and then in the early 1900s scientists observed that the chromosomes and mendel's units behaved in similar ways in terms of inheritance and this led to the idea that the units now called genes were located on the chromosomes in the mid 20th century watson and crick used research from rosalind franklin to work out the structure of dna and the mechanism of gene function when we say that species has gone extinct we mean that every single individual has died out and they are not coming back species might go extinct because of new diseases new predators and here we include humans and hunting a new competitor that's better at getting the food source than the species that's going extinct natural disasters like volcanoes temperature change and also the cyclical nature of speciation which means that one species doesn't exist anymore because it's evolved to become a new species in studying extinct species the fossil record is really important and it's really useful when we're thinking about evolution because the age of the fossil can be determined by the age of the rock which correlates with how deep it is so the deeper in a rock we find a fossil the older that species probably was and the longer ago it was alive when we say fossil we mean the remains of an organism that have been preserved usually in rock but sometimes in ice or in amber usually over millions of years most of the fossils we have are of the rocky type and they form when an organism dies and then layers of sediment so mud and sand form on top usually under the sea and then because there isn't a lot of oxygen bacteria can't decay that organism so over a long time the hard parts like bones and teeth are replaced with minerals and so we're left with a rock that has the shape of a bone or the shape of some teeth left in it and this explains why we don't really have many fossils of soft bodied organisms which includes most of the very early life forms it's also possible to have fossils of prints or of burrows or other traces classification is the science of putting species into groups based on their shared characteristics and you need to know about two systems the old-school taxonomic hierarchy system and also the three-domain system as proposed by woes in 1990. in the three-domain system we have eukaryotes including animals plants and fungi then the true bacteria and finally the archaea which truthfully are as different from true bacteria as they are from us but according to aqa their primitive bacteria usually found in extreme environments we call these types of archaea extremophiles literally things that like extreme environments like high temperature or high levels of salt in the traditional taxonomic hierarchy system we started out with five kingdoms animals plants fungi bacteria and protoptyster which includes slime molds and plasmodium which causes malaria each kingdom is then split into a number of phyla so for instance for humans our phylum is called the chordates and this involves anything that has a spine and a spinal cord phylla are then split into classes classes into orders orders into families and then families into genera and species the last two of these categories are used to create a species binomial name now you might have heard this called a latin name before because a lot of binomial names are in latin but lots of them aren't and we should really use the proper name for them so this is made out of the genus and the species and the genus has a capital the species doesn't and there's a space between them so the binomial name for humans is homo sapiens and this system was developed by carl linnaeus the final unit in paper two of biology is unit seven ecology an ecosystem is the interaction of a community of living organisms so the biotic factors with the non-living or abiotic parts of their environment in order to survive and reproduce organisms require a supply of materials from their surroundings and from the other living organisms that are there animals and plants may compete in trust specifically which means within their own species or inter specifically with other species for both biotic and abiotic factors where a species is able to survive and thrive will be a combination of both the biotic and the abiotic factors for instance an animal species may not be able to survive in an area where there's a superior competitor taking all the food but then also where it lives could be controlled by something like the temperature being too hot or as a plant you might not be able to survive in an area that doesn't have sufficient light so you can't do photosynthesis or where there aren't enough mineral ions in the soil when we talk about interdependence we mean the way that different species interact with each other in order to be able to survive so for instance insect a might be a pollinator like a bee that drinks the nectar of plant c while it's pollinating it and then mammal b might eat the fruit and plant c needs both of those animals because even though they're feeding on it without them it wouldn't be able to make fruit because it wouldn't be pollinated and it wouldn't be able to spread its seeds a stable community is one where all of the species and environmental factors are in balance so that population sizes remain fairly constant over time species become adapted to the environments they're living in and here we're talking in evolutionary time scales so we're not saying that one bear grows a thicker coat because the winter is cold we're saying that over thousands of years the bears with the thickest coats survive best and reproduce more and pass on their alleles and so bears as a whole develop thicker coats you may be asked to describe how animals and plants are adapted to different environments such as how plants growing in the desert have small leaves and fused tomatoes to avoid water loss as well as large root systems to absorb maximum water when it does rain or how animals living in the arctic have white fur for camouflage feeding relationships in an ecosystem can be represented by food chains which can be put together to make a food web like this one in each food chain the direction of energy transfer is shown by the arrows every food chain begins with an organism that can synthesize molecules containing energy and we call these organisms producers most producers are green plants or algae making glucose by photosynthesis producers are then eaten by primary consumers which we can also call herbivores and then primary consumers are eaten by secondary consumers and secondary consumers by tertiary consumers we also can say that anything that kills and eats other animals is a predator and anything being killed and eaten is a prey in a stable community the numbers of predators and prey rise and fall in cycles if you're taking triple science then you should be able to talk about food chains and food webs in terms of their trophic levels and these are just how many different organisms there are in the same food chain so if we take one food chain as an example our first trophic level would be the algae the producer and then the second trophic level is the zooplankton and then the third trophic level is the big fish and the fourth trophic level is the seal it's very unusual for a food chain to have more than four trophic levels the seal and also the herring girl in this food web can be described as apex predators because they don't have any predators of their own as a triple scientist you should also be able to describe food webs in terms of pyramids of biomass which literally show the mass of living organisms at each level the energy for the food web or food chain originally comes from the sun and plants and algae are able to lock up about one percent of the available energy by doing photosynthesis then between each trophic level approximately 10 of biomass is transferred the vast majority is lost either because of food waste so for instance a predator doesn't actually eat all of its prey it's lost as feces or also large amounts are lost from doing other activities so if you think about all the energy that you take in today most of it is going to be used with you moving around or just keeping your heart beating it's not being used to gain weight and put on muscle mass the ecology required practical centers around measuring the population size of a common species such as clover usually in response to an abiotic factor like light moisture content or ph to estimate the population size you use this piece of equipment which is called a quadrat it's a square frame and it often has divisions inside to help you to estimate what percentage of the quadrat contains the plant you're sampling depending on your exact investigation you may be comparing two separate locations or looking at a transect which is a long straight line where an abiotic factor changes gradually if you're comparing two locations you use random sampling at each location to ensure you have a fair representation split the area into a grid using coordinates and then use a random number generator to tell you which squares to sample for instance square b1 and c5 at each location you sample the coverage of the plant using the quadrat and you also take a reading of the abiotic factor such as a light reading with a light meter or measuring acidity with a ph probe if you're looking at a factor that gradually changes such as moisture content as you get closer to a river then instead you use systematic sampling you use a long tape measure to make a line called a transect and then you put down the quadrat at regular intervals along the way say every five meters again at each location you survey percentage cover and your abiotic factor there are some opportunities in here to test your math skills and these usually involve working out the area either of the whole sample site or the quadrats that have been surveyed these are usually quite easy calculations to do but also easy to make silly mistakes with so do check your working materials are cycled through ecosystems as part of both biotic and abiotic processes you could be asked about the water cycle which provides fresh water for animals and plants or the carbon cycle which contains biotic and abiotic processes the total amount of carbon in the atmosphere in form of carbon dioxide is increased by respiration from animals plants and microorganisms as they break down glucose and release carbon dioxide it's also released by decomposition in which microorganisms break down dead plants and animals and then release carbon dioxide into the atmosphere as they respire and mineral ions like nitrates into the soil carbon dioxide levels are also increased abiotically by the combustion of fossil fuels meanwhile carbon is removed from the atmosphere by photosynthesis in which green plants and algae absorb carbon dioxide and make glucose they then store this as starch or use it to make fats proteins and cellulose carbon dioxide is also removed when it dissolves in oceans and forms into carbonates which are locked up in sedimentary rocks and also by the production of fossil fuels and peat carbon can also be transferred between plants and animals when animals eat plants microorganisms play a vital role in agriculture by causing decomposition or decay this releases carbon dioxide into the atmosphere and mineral ions like nitrates into the soil where they can be used by plants decomposition such as in compost heaps occurs fastest when it is warm with sources of water and oxygen if there's insufficient oxygen available then methane gas may be produced which is a greenhouse gas and can also be used as a fuel called biogas many remote communities have biogas generators which they feed with domestic waste to allow them to create enough biogas if you're taking gcc biology then you would have done the milk required practical which is meant to be about decomposition even though it really isn't decomposition it's just another optimum conditions for enzymes working practical you start with tubes of milk lipase enzyme and sodium carbonate and these are put into a water bath at a particular temperature and a thermometer is used to ensure that the tubes have all reached that temperature before they are mixed together then as the lipase enzyme breaks down the fats in the milk fatty acids are released and the ph is lowered you can measure this using a ph probe and you can see how long does it take for the milk to reach a particular ph the experiment can then be repeated with tubes at different temperatures the faster the ph falls the closer to optimum temperature the enzyme is if a ph probe is unavailable then you can still achieve valid data by using a ph indicator that changes color but this is much more subjective than using an instrument in this experiment your independent variable is the temperature that the tube's at your dependent variable is how long it takes to reach whatever ph you've chosen or to see a color change and the control variables will be the volume of milk the volume of lipase the volume of buffer and also the concentration of the enzyme it's important that you're saying volume because just amount is unlikely to get you the mark biodiversity is all about having the maximum number of species possible in an ecosystem and the reason that we care is that this makes the ecosystem much more resilient and able to resist change for instance if a disease causes a particular plant have reduced numbers and it's the only food source in an ecosystem that many herbivores may die and this has a knock-on impact up the food chain however if there are several other plant species then the herbivores may be able to survive for a year by eating those instead while the population of the first plant recovers there are lots of things that we as humans can do to protect and preserve and encourage biodiversity including running breeding programs for rare species in zoos and in nature reserves protecting and regenerating rare habitats reintroducing hedgerows around fields rather than just having large prairies of monoculture reducing deforestation recycling more and also conserving peat bogs unfortunately there's also plenty that we as humans do to harm the environment including polluting the water with sewage fertilizers and toxic chemicals the air with smoke and acidic gases and the land with landfill and leaching toxic chemicals too we also reduce the amount of land available by building on it quarrying or mining it farming it and dumping waste there for landfill and we've carried out large-scale deforestation not just because we want the wood but also because we want the space for cattle and rice fields or for growing crops for biofuels carbon dioxide methane and water vapor are all examples of greenhouse gases which are molecules that will trap infrared radiation causing earth to warm up having a little bit of them is a good thing because it keeps our temperatures stable and also high enough that we can actually live on earth but unfortunately we now have too much of them and this is leading to global warming these greenhouse gases form a blanket around the earth and it's possible for small wave radiation like visible light uv gamma and x-rays to get through this but when that radiation reaches earth the earth absorbs it and then re-emits it as a longer wavelength wave like infrared radiation now that infrared radiation is too large to easily pass back through the blanket and although some of it does get through some of it is trapped and warms up the atmosphere and earth's surface the rising temperatures caused by this are leading to lots of serious consequences as the ice caps melt sea levels rise and this can lead to flooding and other extreme weather events like droughts and hurricanes polar habitats are being lost and with them many species are going extinct food security is a term used to describe having enough food to feed a population and it's a major concern of governments around the world a country's food security could be threatened by any number of factors including an increasing birth rate which means that there simply isn't enough food for the number of people in the country changing diets particularly moving towards more consumption of meat which is incredibly energy inefficient it's possible to feed far more people on a vegetarian diet than one in which people are consuming meat every day also there are new diseases that affect farming and environmental changes like droughts which lead to crop failure and famine the cost of agricultural inputs like mpk fertilizers can be prohibitive and make it really hard to produce affordable food and also conflicts like civil wars can affect the availability of food and water trying to meet the food security needs of a country can lead to some questionable farming practices including factory farming in factory farms animals are given very little space in order to minimize energy losses from them moving around a factory farm chicken may spend its entire life in a cage the size of a piece of a4 paper they're also kept in warm conditions so they don't use energy shivering and trying to keep themselves warm and they're fed a high protein diet in order to help them build muscle mass a similar mentality has led to significant overfishing which governments are now trying to rectify by regulating the size of nets that fisher people are allowed to use so that they don't destroy all the tiny baby fish that aren't big enough to breed yet and by introducing quotas where there's a maximum amount of fish they're allowed to catch and if they catch more than that they won't be paid for them finally biotechnology and biotech has lots of applications both in food security and also elsewhere in our lives mica protein is protein derived from fungi and it's often used as a meat substitute by vegetarians a fungus called fusarium is grown in order to produce the microprotein that goes into things like corn and it's grown on glucose syrup as an energy source and in an aerobic environment so it has plenty of oxygen from there it can be harvested and purified another food related thing we can do using biotechnology is to fortify nutritionally poor foods rice is a great source of carbohydrates but lacking in vitamins and if you're deficient for vitamin a then this leads to night blindness and other serious medical problems with your vision but many peasant farmers throughout the world don't have access to red and orange vegetables containing vitamin a and live almost entirely on plain rice by transforming rice with three genes two from an orange daffodil and one from a bacterium scientists were able to develop golden rice which is orangy yellow in colour and can make and store beta carotene which your body can then use to make vitamin a this has helped the people who eat this rice to avoid serious health problems in the days before genetic modification diabetics had to treat themselves using insulin taken from pigs and cattle and although the hormone is quite similar in other mammals it's not identical and so it doesn't work quite as well nowadays of course we've genetically engineered bacteria to make the human insulin protein for us so it's very cheap and easy to produce large quantities without any concerns for animal welfare thank you very much for watching and i hope you found that a useful summary of all the content in aqa gcc biology paper 2. good luck for your exams and if you did find it useful don't forget to like and subscribe you