The Whole of AQA Biology Paper 2. B2. 9-1 GCSE science revision



hello ello Polly kittens this da cuz everything he needs your second biology exam for a key a if you want to follow along everything we do in this video get all the student for any certification statements make sure there's nothing that you've missed out you can get that my free everything going over my website loads anticipation statements laziness pictures for you to feel it in as we're going through pages and pages and pages of keywords or biology crosswords to make sure you know all of those all of your units of physics are also in there good luck guys if it's anything you need just let me know homeostasis is the maintenance of a constants internal environments and keep your body functioning properly we need to control our blood glucose levels our water levels and our temperature the brain is the control center and that's going to be sending signals to various parts of the body for example to the pancreas which is responsible for producing insulin mmm affect his muscles are going to do things like moving for example shivering and then glands are going to be responsible for the production of other hormones nervous system is incredibly complex and is overlaid on our spinal and muscular system it consists of the brain spinal cord which today are going to make the central nervous system or CNS and all the neurons the receptors and effectors when you pick up stimuli that signal needs to travel from where you picked up so your fingers all the way up to your nervous system your central nervous system sometimes just stopping at your spinal cord and then coming straight back again that is going to be a reflex this is going to happen when you touch something hot so you move your hand away without even thinking about him other time something is going to happen the signal grabs your brain you'll think about it and then you'll decide to move the nerve cells involved in this I've a really long so this cell body here is incredibly long and this can send a fast electrical signal however when we come transfer a signal from one nerve cell to another nerve cell things slowed down a bit because they have to cross a synapse this is going to be a slow chemical signal as the chemical has to be released diffuse across the channel and then we picked up and then initiates another electrical signal here we have male and female an endocrine system the purity guard is in the brain thorry wood is in the neck you turn around when the kidneys pancreas is hiding behind the stomach ovaries are called a right hip level and then testes Hanalei the penis the testes produce testosterone which has the effects of growing muscles making the balls and penis drop and grow larger increasing the rate of hair growth East Asian is producing the / that is responsible for the maturation of eggs and the menstrual cycle the pancreas produces insulin which is important for creating blood glucose levels the adrenal glands produce adrenaline which is reporter for our fight-or-flight response the thyroid produces thyroxine which is important in regulating our metabolism the pituitary gland is very busy among other things it produces follicle stimulating hormone FSH and luteinizing hormone LH control of blood glucose is very complicated after a meal has been eaten a blood glucose levels start to rise this is picked up by the pancreas the pancreas produces insulin which is sent out into the blood the insulin in the blood stream is going to cause our body cells to start to remove glucose from the blood liver and muscle cells can take the glucose and convert it into glycogen and store it removing glucose from the blood will cause blood glucose levels to fall if blood glucose levels gets too low this is also picked up by the pancreas the pancreas will start to produce glucagon the glucose has previously been stored in muscle and liver cells starts to return to the blood the most complicated part of this is getting all the names right the stored form of glucose is glycogen glucagon will convert that into glucose and this returning the glucose will cause blood glucose levels to rise again there are two different types diabetes type 1 and type 2 in type 1 diabetes the pancreas doesn't work properly so it doesn't produce the right amount of insulin in that type 2 diabetes cells starts become insensitive to insulin symptoms for both are going to be a loss of whites and increased needle we being very thirsty blurry vision fatigue so being very sleepy and hunger treatment for type 1 diabetes is going to involve intern injections type 2 diabetes it's going to be controlling diet exercise one of the reasons periods feel so rubbish is cause your hormones are literally all over the place starting with follicle stimulating hormone it rises Peaks and its job is to make the small egg grow up to a larger egg and then be released luteinizing hormone is only active for a very very short period it's job is to release the egg Easter Jim builds up until it stimulates luteinizing hormone progesterone builds up slowly as it builds up the lining of the uterus and if there is no eight of his resident embryo implanted in it that would decrease and the lining of the uterus will break down there are a number of different methods or contraception some hormonal some non hormonal that will stop you getting pregnant but not all of these will protect against sexually transmitted diseases so is always very very important that you wear a condom this is a barrier method of contraception this will stop the sperm getting and the woman pregnant and it will also stop the nasties that occur in between transmit it from her to him or from him to her the pill and the coil IUD into trying device our hormonal methods of stopping getting pregnant they're going to stop the egg being released or the egg being implanted the diaphragm is a barrier method because it will stops entering the vagina but the semen will still be transferred into the vaginal entrance so that you can still get sexually transmitted diseases this way if you're sure that you don't want to have children even like those to be sterilized you could have a sex me you have your tubes tied which will mean that no sperm will get from the testes out to the penis or for the woman no a core will be released around 1 in 6 people will find themselves in the unfortunate position where they can't have children naturally about half this due to male related reasons and half this is due to female related reasons as you can see only and one of those people and last year 2016 we did IVF and this is my massive bump so the obvious advantages for IVF are you get the baby out of ended and and if you've been in a situation where you can't have something that you really really want you know it's very very sad and a picture made how is quite a lot so having a baby is gonna be good for people that want to have the baby that mental house however the disadvantages are you have to take a large large number of drugs for a very very long period of time and that these have very nasty side effects as well as the daily injections which leave you horribly braised and you there are long-term consequences for these because taking these IVF drugs increases your chance of various different types of cancer it is very it's very very expensive I had to have it twice that's twice as expensive doesn't always work there is about a 40% success rate with IVF with each round of IVF costing a minimum 5,000 pounds we the food since exists right here with a large number of drugs like today a good day by day it's a very costly time-consuming painful process mitosis will lead to two identical daughter cells whereas meiosis will later four different daughter cells you can remember mitosis those two t because you have the DNA mitosis Easy's of things like growth or repair well as mices is used for sexual reproduction so these are going to be gametes in mitosis we are going to end up with diploid cells and in meiosis we are going to end up with hack right sense haploid cells having half the number of DNA as the original cell in women the gametes are eggs and in men the gametes are in a plant we have eggs still and that is in the stigma and then the male gametes in plants are pollen and that is on the statement in meiosis we are going to have two divisions so our chromosomes will line up they will sort themselves down the middle there will be a little bit of crossing over going on so they will swap chunks of their chromosome to increase the genetic diversity they will divide into two then they will line up and divide into two again and you'll notice that each of the cells have half of a number of DNA as the parent cell asexual reproduction is very common in the porn world strawberry plants boil plants and in bacteria and fungi you are going to get a genetically identical population as these are dividing by mitosis so all of your cells are going to be the same let us just pause for a moment luckily be useful pictures and then we can start again gene is a stretch of DNA the case for a characteristic genome is all the genes in a body all of the genes that you have a gamete is going to be a sex cell so in humans is a sperm or other egg chromosome is bundled up DNA alleles are different versions of genes Domino means you'll need one gene to express characteristic recessive means you need two identical recessive genes to express characteristic homozygous measure genes the same heterozygous major genes the difference genotype is what genes you have phenotype is the collection of characteristics that you have we can work out the chances of a disease or a phenotype being passed on but doing a genetic cross these were things I think should be laid out very formally Umbro populates a mothers genotype big R little R mother's feeling tribe is a carrier for this phenotype big R little R father's phenotype a carrier mother's gametes oh now we can meet some mother's gametes over here oh and the father's down here and then fill in these ones down and these ones across so the mother oh then this one down oh the father this one of course and then the father this one across then of the spring are going to have dominant dominant today can it be homozygous or non suffer two of the potential offspring or half the potential offspring are going to be heterozygous in a carrier and then out of the offspring one in for them has chance of being a double homozygous recessive and being a sufferer polydactyly it's a condition where the people get one two three four five six little adorable baby fingers and it is dominant so here we have a mother who has two homozygous recessive and five fingers and a he has a dominant and recessive and has six fingers we can feel in the genetic cross mother mother mother father father father and we can see somebody who has these dominant disease if they have one gene they'll pass it on a fifth or that officer has a 50% chance of also having polydactyly cystic fibrosis is a recessive disease so as we saw in the first example if we have two parents that are carriers there is a one in four chance of an offspring having at the disease if only one parent is a carrier then there are chunks of the baby having my sister of aces or virtually nothing apart from for any mutation and transfer them being a carrier or 50% if your family has a known genetic disease or if you have a child that had a genetic disease you could opt to have IVF and before your embryo was implanted back into you you could have it's screen so embryo screening or pre-implantation genetic diagnosis the advantages to this are that you can test the embryo so it only put back healthy embryos so that chant saw the baby born is going to be healthy and is going to survive or you can have an embryo implanted which could help be a match a genetic match for a sibling already born the disadvantages of this is that embryos are going to be created and destroyed and some people have religious objections this no chromosomes are in the nucleus and you have 23 heads so that is 46 in total I say 23 pairs because you're going to get one copy from the mother and one copy from your father so you'll have 2 cups of chromosome 1 2 cups of chromes into two cups of chromosome 3 2 comes to chromosome 4 1 from your mother and one from your father this will allow for you to be homozygous or heterozygous for the dominant or recessive genes if you have inherited two x chromosomes you're going to be genetically female if you have inherited an X and a wire chromosome you're going to be genetically male if you know that they are identical twins you'll know that they are not exactly the same even though their genotypes are the same while they have identical genes their phenotypes are characteristics and how they look are going to be very different because your phenotype is influenced by lots of different things firstly your genotype so that's your DNA your genetic information and your environment this is going to lead to natural variation in a population things are going to lead to variation in a population are going to be influences like diet exercise and personal choice making new copies of cells involves copying DNA over and over again and if you try copying something down thousands millions of times eventually they'll become a mistake and this mistake might just happen once and then get forgotten or this mistake might be copied over and over and over again and if it gets copied over and over again we've got a mutation and we've got a natural selection all of these changes added together these small changes these big changes this is our theory of natural selection of evolution of gradual change happening over time this theory thought up by Charles Darwin that means we are more suited to our environments Darwin's theory is that life all life that we know these days has evolved over the past three billion years from the first life there's very very simple you see little organisms that's what in that slushy puddle and the way this evolution happens is via natural selection so that random mutations in genes nice and natural variation in a population so that can be small things like different hair color different eye color or big things like how tall people are so for giraffes being tall is quite an important things it means I have access to a larger range of food sources and individuals characteristics which make them better suited to the environment are more likely to survive and reproduce whether this is tall giraffes or finches with difference 8 beaks or moths that have gone black Corrigan wines and the jeans these useful these desirable characteristics will be passed on to the next generation evidence for evolution comes from fossils I'm not everything at least was always because fossils come form of the hard parts the bones the soft bits are just going to decay away so won't leave fossils and we can see evolution happening with bacteria because they multiply very quickly twenty minutes and some circumstances so we can see changes adaptations for natural selection being passed on and happening very very quickly fossils can show us changes that have happened and how different animals are related from these we can use or draw an inflationary tree showing us how closely things are related to things and more March interior closely related and the point where they branch off that's where their became genetically distinct when a single species of animals gets geographically separated and this could be because there were on different islands or there could be a mountain range that pops up in between them then we had known end up with a situation when we have speciation where one species leads to various different species and this is called speciation Darwin saw this when he was over in the Galapagos Islands the finches small and birds all started off as one population one species but as they separated out on to the islands of theirs they got separated from each other they became quite different the main difference was in the shape and length of that beaks as they became more adapted to the food sources on those different islands so either had to dig down deep to get the food or whether the food was on leaves whether if it was hard to eat when food was easy to eat I think we can take a second to appreciate how thoroughly cute these little guys are before we start to talk about the serious issue of selective breeding selective breeding is breeding an animal for a particular characteristic it happens with dogs it happens with cows with horses with cats with chickens any animals that we keep and we look in the particular characteristic have probably undergone selective breeding and the advanced assists are is that your animals which have the desired characteristic whether it's a very flat face of a park or horses that run fast or cows that produce a lot of milk it is important commercially that dairy farmers have cows that produce a tall milk that dog breeders have dogs that look cute however the disadvantages to this is if you have a healthy animal who doesn't display the side characteristics for dairy farmers they are looking for cows that produce that are a milk these obviously going to be female cows so any male calf's they're born they are healthy animals but they are not showing desired characteristic so their kills um dogs that don't show the desired characteristic can be purchased sleep even though they're perfectly healthy animals thousands of dogs cats each year are killed just because they are not cute enough or do not look like the industry standard the desired characteristic can lead to long-term health problems for their animals I've chosen the Pug as the example here because of the large number of folds on their face it squashes their little nose and it gives them real long-term breathing problems dogs likely Labradors are very susceptible to things like arthritis and dogs like weird eating which backs though desired characteristic ears and mutations any dogs are born without the which bag can be put to sleep and then lastly we have a lack of genetic diversity within the population so when we're talking about breeding this can lead to a lot of inbreeding we're brothers and sisters are bred to get the desired characteristic which is going to lead to recessive bad mutations coming out more often in the population it also means they're going to be more susceptible to any diseases that are going to be around because they don't have the genetic immunity genetic engineering has brought around some fantastic advances one of them were useful of this is the way we produce insulin these days previously in Qin used to be harvested from pig cells and that's what people had to inject it wasn't very good and it wasn't very efficient these days we've taken the gene for insulin we've taken a bit of bacterial DNA and with the original DNA has our side characteristic and bacterial DNA reproduces really quickly the insertion of the gene for insulin into the bacterial DNA means that the bacteria are now producing insulin so we are now producing large amounts of human insulin which is a really important point quickly and safely this is much much better people than having to inject Pig insulin it's me thing as much cheaper much faster and much say we can genetically modify plant DNA so we can take a DNA we have a quiet characteristic whether that is a drought resistance gene so there are countries that don't get much rain in a very very susceptible to droughts can survive that better so their crops are going to grow better whether that's a gene which produces a vitamin so that countries that don't have a good few security where food is shortage where people are dying because I'm not getting wise man spit means we can engineer the food the rice that they're growing so that it produces more vitamins so it's healthier so that less people are going to die or whether it's just pesticide resistance or the ability to resist being eaten by um pests being eaten by bugs say that yields are higher we can take that gene and put it into our original plant DNA producing a genetically modified plant we can add in the new gene to the plant DNA we can produce seeds and then the farmers can grow vases and the plants will have this a new desired characteristic some people don't like genetically modified plants because they think it's interfering with nature another mental break let us all just pretend for a moment we're Instagram travel bloggers actually divide very very rapidly bacteria is happy has lots of theater has lots of space and nutrients he's going to divide roughly every 20 minutes this allows sinew mutation to spread through the population really quickly this is gonna ruin our antibiotic resistance to really easily develop and spread due to brandy mutations if those weren't a mutations that mean that the bacteria didn't get killed by antibiotics they're going to be flexible by natural selection I'm actually very easily passed from person to person or from an animal person or from an animal to animal which means antibiotic resistant bacteria is going to spread it really easily penicillin has saved many millions of lives probably yours at some point definitely mine because before penicillin before the widespread use of antibiotics people died of very very common things Conant hospital to have a simple operation most of the time was lethal but for widespread use of antibiotics the smallest infection could kill you mr sa is a bacteria that is resistant to most antibiotics now this happens on your skin is there on your skin all the time if you go into hospital abrasion you'll get swept for it to find out if you have it but if you do have it underneath an infection with it there are very few antibiotics they can use to treat it the development of new antibiotics is very slow partly because we've looked for all of these in a lot of places and partly because raping new drugs is very very expensive so companies are going to spend that time spend their effort and their resources licking out drugs that are going to make them a loss of money drugs that people have to take every day for heart disease or diabetes antibiotics you take once for maybe seven days and then you don't need them again so they don't necessarily make pharmaceutical companies lots of money but they will cost lots of money to develop color nails develop taxonomy which is the study of grouping living things together we can see on our evolutionary tree here that some things are very closely grouped together and get the other things you actually have to go quite a long distance he develops a naming system where we have each organism hires a to part in that name and this will tell us how closely related they are it's a bit like them having a first name and a second name at genis and then a species the genus will be the wide overarching type of thing and then the species will be exactly what thing it is with each new development in biology with each new development in genetics we understand more and more about classifications so our taxonomy and our evolutionary tree is evolving all the time the three domain system divides everything in life into three groups eukaryotes bacteria and archaea eukaryotes are things that have nuclei an ecosystem are the animals plants everything living within a certain area the community of the plants or animals that live there and they're all dependent upon one another they cannot survive without each other for example the animals eat the plants they can't survive without doing that and the plants rely on the animals to dispute their seeds to survive and refugees our species needs food water air and sometimes were not always a mate abiotic and biotic factors are things that are going to affect any organism abel took on nonlinear factors such as light intensity temperature water levels pH iron levels wind carbon dioxide levels and oxygen levels biotic factors are going to be living factors such as food predators and pathogens an increase or reduction or removal or introduction of any of these factors can have a dramatic impact on a community for example the introduction of a new predator or new pathogen could wipe out a community an increase or a decrease in the temperature could mean that their own organisms food source is gone all organism can't survive in that environments and plants and animals aren't going to be able to survive without sufficient levels of carbon dioxide and oxygen animals need to adapt to our environment so that they can survive cacti are well adapted to a desert environment because they have shallow roots they have spines to prevent them being eaten and they can store water in their leaves snow foxes are white so that they blend in they have small ears so that they don't lose heats was able to use a surface area and they have a very thick coat all three chain starts in the same place with the Sun provided energy and then from this energy things are going to grotty mainly plants and they get eaten by other things whether it's grass being eaten by cows and then going on to be eaten by us or whether we eat the plants directly or whether plants hear the call is being turned into concert which is used in ketchup as we eat them directly or process them we are King Jima whereas other things like Cal's are gonna be hurtles because they just eat plants the direction of arrow is really important in sea chains directions that are a means eaten by if you want to investigate what grows and it feels you can use a hot rock which is going to be lets say a meter square you throw that on the ground and count what is in there randomly moving it around the field so that you get a wide coverage you're going to need to estimate the size of the fuel so that you will can work out how much area there is work out your plant population per area that you even measured as then multiply that up to cover the entire field a transect is it more ordered you start at a point take a line and then take measurements at every single point along that line this could be saved from a hedge moving away so that you are varying things like the light intensity or distance on water so for the carbon cycle I'm referring a lot to organic compounds and if you haven't heard this phrase before it can be a bit confusing organic compounds are just any compound that has carbon in it and just remind you a compound is two or more elements that are chemically bonded together so here will different locations that carbon can be it can be carbon dioxide in the air or conducts very desorption oceans it can be as organic compounds in plants or in animals these were going to compounds can also present in the dead plants or animals and they are in the fossil fuels now you need to know that various different ways that they change from all these different locations and what processes are called so let's start with fossil fuels when we have fossil fuels we can burn them so that the carbon in them going into the fair and the fancy name for this is combustion and when the carbon dioxide is in the air it can be taken up by plants and this is a process of photosynthesis and the opposite can occur as well because plants were also under the respiration plants get eaten by animals and then plants and animals both die from the organic compounds that are in the dead plants and animals they can turn into fossil fuels by either either mean buried or being sedimented or they can just go straight back up into the air or by the process of decay and then lastly our animals are also undergoing respiration so carbon is an aesthetic thing it is constantly moving around from carbon dioxide in the air to carbon compounds are in animals plants in dead animals and then being inserted into fossil fuels which them then meat birds and put the carbon dioxide back in the air this is a very very commentated involved process that happens over millions of years and you need to know all of these steps the water cycle is much more complicated than you think it is going to be he energy from the Sun comes down warms the surface of the water on earth and this is going to cause the water to evaporate as also evaporates it's gonna become a less dense it's going to rise up and then it's going to condense when it starts to cool down this is when we're going to get clouds forms when their clouds are heavy when the water is accumulated so much it is going to start to rain and the fancy word for rain is precipitation after its rained the water is going to do a number of things you can go into the mountains where it will sink in or percolates deep into mountains ways then going to pick up stuff like ions salts which is going to affect the taste and the chemistry of the water this will then come out somewhere as a little stream and go into the river some of its going to go into the soil moving slowly back towards a river or a lake f3 flow some of the water will go straight onto the ground if the rock or the mud is already saturated if it is full of water or the rock is impermeable and that will just run off into the nearest river or stream or lake or reservoir all of it ending up at some point in a large collection of water whether that is in the sea again or whether that's in a reservoir or whether that's in a lake some of that water will get taken up by plants I used in photosynthesis it will also come out of plants in a process of transpiration and then go up into a flower and then the cycle starts all over again microorganisms are part of the system of biotic and abiotic factors that help break down old things for example old food so that the components can be recycled back through the system biodiversity is the range of plants and animals that live within a habitats and humans have a massive impacts on biodiversity whether it is chopping down loads of natural fields so that we can plug the same type of crop over and over again reducing the biodiversity in that environment because we're replacing it with the same type of crop or whether we're talking down fields Forest City we can replace it with cities there are a wide range of different types of pollution whether it's air pollution from the smog water pollution where oil or rubbish is getting into the water or plastic pollution where we just live in rubbish all over the place and this could have a dramatic impact on the plants and animals that live there if we changing the chemistry of the water that they're living in if you're pumping in nitrates or fertilizer or if you're having in to watch oil the fish and the plants are going to struggle to survive with plastic these being eaten by animals and the chemicals in there are moving up the food chain and air pollution is having a massive effects on the animals not just the breathing but whether they can thier ability to camouflage large parts of the world's are suffering from deforestation of my own where the trees being cut down either for logging so the trees the wood can be used also that the land can be used to grow things like crops the problem with deforestation is that it destroys habitats for the plants and animals and if this is happening in a rainforest where there are lots of rare animals or animals that have yet to be discovered then these animals are losing their habitats so they can't be protected it leads to soil erosion so the so that worth held together by the wreath isn't held together and I'm also a trained star just washes away I'm a source of nutrients peat is basically mud it's complicated Francie might be it's basically mud and this can be used for burning and what they do is they chop it outs of the grounds in square chunks it needs to be left in the Sun to dry and then it can be used as a fuel the problem with chopping this out of the grounds uses fuel is that it has taken millions of years for this to grow so it's a non-renewable resource and it provides a fantastic habitat for plants and animals and once it is chops up and burnt that habitat is lost there are a number of gases that contribute to global warming we have carbon dioxide water methane being the main ones and global warming might be a slightly confusing term because not everywhere is getting hotter some places are getting colder some places are getting drier some places getting windier this is climate change going on so while Australia may be having its hottest Christmas ever we could be having our coldest Christmas ever here in the UK and this is all due to global warming or climate change this is going to have massive impacts on animals predominantly on their habitat and their food sources polar bears live on ice caps they hunt they fish and then they need to go and rest on floating blocks of ice if the poles are getting warmer and the ice isn't there that it's gonna melt polar bears after a longer time fishing won't have anywhere to rest and are at significant risk of drowning how it hats are also spreading for example as the top of a mountain warms up mosquitoes can move further up the mountain changing the location of where plants can grow your wet animals can live if a region is too hot or too cold food may not grow there anymore the plants or the animals that another animal service on which is going to leave a species vulnerable if their food source has been wiped out well done for making it this far guys it's what these video mine science can go and have a break now the Restless is biology only the brain is control central body it makes sure everything's functions properly and tells various different parts watch do we have the cerebral cortex the cerebellum and the medulla the brain is an incredibly complicated thing study because for it to be functioning properly it needs me inside a living person doctors can work on mapping various different things by using MRI scanning and CT scanning they're giving their person different stimuli to see which parts of the brain light up here we have our beautiful picture of the eye sclera which v is the white bits the retina which is where the image is focused the optic nerve which sends message to brain the ciliary muscles which change the shape of the lens the cornea which is a protective covering pupil lets light in the lens is responsible for focus and the suspensory ligaments hold the lens in place if you are short-sighted you can't see distant objects and if you're long sighted you can't see make subjects in an eye that can see correctly the lens will take the light and will focus the image on the retina whereas someone that is short-sighted the image faces before the retina and someone that is long sighted the image focuses behind the retina to correct shortsightedness we need a diverging lens and correct long sightedness we need a converging lens body temperature is going to be regulated by the Greg ray story thermo regulatory center in the brain if you are too cold that hairs on your body or stand up this is to trap a layer of air you're going to stop sweating raise a constriction more starts so your blood vessels walking strict so that they're further away from the skin less blood is going to flow close to the surfaces skin so less heat is going to be lost from it and your muscles are going to start to shiver and move when it's going to produce energy if you are too hot your hairs are going to lie flat so they're not trapping any air you're going to start sweating and the water is going to evaporate leading to heat and energy loss and your brother sores are going turn to go they say dilation means they're going to get wider so that blood can flow flow such as surf is his skin so that he can be lost the kidneys have three functions they remove yumiya they control the iron content and they control the water content of the blood there are three ways we can lose water from our body in urine and sweat and when we breathe out it's important to control the level of water in the body because there is there's too much water to use too much water taken up by cells by osmosis and they might pop order there's not enough water than the enzymes the functions the reactions won't be hard to take place there are three steps away that they kidneys function ultra filtration reabsorption and then the release blood enters the kidneys under high pressure and water is UV and sugar are gonna be squeezed out into the capsule which is it starts at the nephron as this all flows along the nephron useful things will be absorbed all of the sugar is going to be absorbed by active transport some ions there magnifiers that we need the tyre finds that we need are gonna be reabsorbed by active transport and enough water that we need is going to be reabsorbed the hormone that controls how much water is going to be sold is a th which is antidiuretic hormone and then anything that isn't reabsorbed is going to come out as we if kidneys aren't working properly a person can under get kidney dialysis the dialysis machine will take over the function of the kidneys but it is very time consuming it takes about four hours and has to be done three times a week so this has a huge impact on someone's life and it's not a lot of fun an alternative to dialysis could be kidney transplants but these come with very long waiting this and there is always the risk of rejection phototropism means something is going to go towards the light Geotourism or gravitropism means something is going to go towards gravity meaning your roots always gonna go downwards and your shoes always gonna get upwards gibberellins are important for growth Ethan is important for ripening plants and auxins are important for growth nagging Oduya growth in the right direction the advantages of sexual reproduction is that your get a genetically diverse population which means they're going to be better protected from diseases the counselor is a disadvantage of asexual reproduction is that you're going to get a genetically identical population so that if disease comes along and one plant is susceptible Trance up all plants the whole revelation or animals are going to be susceptible and the organs we worked out at once an advantage of asexual reproduction is that there is only one parent meaning that the plant or animal doesn't have to wait around for a mate to turn up whereas with sexual reproduction a mate is required and sometimes this can be quite hard to find especially in sparsely populated locations another advantage of asexual reproduction is that their energy is conserved and what I mean by that is that the parent is putting all of its energy into conserving its ownit genes so this is like The Selfish Gene it wants its genes its genetics to be continued as opposed to continuing putting energy into something that only has half or its genes DNA is made from different bases that fit together so we are always going to have a connecting to T we are always going to tell C connecting to G this is always always always going to be the case it has a sugar phosphate backbone and they return away around the outside there are chair days it is a double helix you see that the green is always connected to the yellow atcg the blue is always connected to the orange and it's going round in a helical or a double helical structure each three-letter sequence of DNA is going to code for an amino acid so here we have a G a we starts off with a thorn G and point a so that DNA sequence is going to code into the amino acid arginine the next three along CTG are going to code into leucine and this will keep going until eventually we have a long amino acid chain this can then fold up in very complicated ways until we get a protein that will look something like that and proteins are responsible for basically everything that happens in your body there are the hormones there the enzyme there the cell walls everything is a protein or dependent upon a protein and these proteins are very very specific and enzyme substrates active sites is going to be very very specific to the substrate so if there is a mistake in our amino acid chain if something is missing or if something is wrong we put the wrong amino acid in there then our enzyme our protein is going to fold up wrong with the mutation is going to have caused a change in the protein which can then have a massive impact on how it functions meaning that it might not work properly meaning that it might not break down what it's supposed to break down meaning they might not function in the correct way there is a massive amount of DNA in each of ourselves and only some of it is useful so say this section here might be non-coding which basically means it's like junk DNA you're just getting in the way there is a number of different ways that cloning can take place we can do it with the plants where we just chop a little bit of pop that into something like rooting hormone put it into the soil put it into the new pots and it will grow into a new plant this works really well with things like lavender or strawberries we can serve our tissue hojo or we can let one cell divide then we can take that put it into further petri dishes until we have lots of dishes of the same we can clone animals by embryo transfer so an animal a sheep a cow anything that the farmer wants to have you nearly once his animal to have lots and lots of genetic babies more than they can naturally have at one time the egg isn't me from this animal this is going to be mixed with sperm from the desired other parent the embryo is then allowed to develop and at this point they can do pre-implantation genetic diagnosis to test for the sex of the animals so it's important for dairy farmers that the cows that are born are female or if they're looking for particular characteristics they can test for those they can only do this in animals easily or to do this in humans so it is perfectly safe to take that embryo remover so to do the genetic diagnosis and then divide it up so you will have 812 identical embryos developing once these embryos have developed the embrace can be implanted into surrogate mothers so the more generic the identical animals with desirable genetic characteristics can be born at once many more than the natural mother the biological mother would actually be able to carry safely if there is one particular animal that you want to clone even me the body cell from that animal take the DNA out of that body cell take a different female animal and remove an egg cell remove the nucleus from that egg cell DNA from animal that you want to clone is inserted into the egg cell it is stimulated to make it divide and then an embryo or develop the embryo can then be implanted into a surrogate mother who gets very very pregnant with a clone of the original animal the baby ball will be genetically identical to the first animal the surrogate mother may also be the animal that the ache was taken from but it doesn't have to be it can be a third completely different animal and then the baby animal that is born is not going to be related or genetically related to a surrogate mother or the mother that donated the egg when Darren proposed his theory of evolution it was very controversial there were lots of religious objections this is because he was saying that the earth was billions of years old whereas that's not what it says in the Bible he was saying that we were evolved from monkeys are evolved from primordial soup and that's not what it says in the Bible an alternative theory at the time is that acquired characteristics so for example if you dyed your hair blonde during your lifetime anyhow baby while your hair was blonde your baby would have blonde hair Bullock's worked with Darwin they published a paper together and Wallace was very important when were talking about speciation geography Mendel worked with sweet peas and he discovered or was the precursor to discovering of genes or units information that um trans inherited units of information decay and decomposition are breaking down organic matter this generally happens by microorganisms and my cordless is alive and this sort of needs to think about when we are looking at how temperature water and oxygen affect the levels of decay they are not going to work at very very low temperatures they are going to rather narrow centimetres which they're going to want to work in they rely on enzymes to break things down they are going to slowly be increasing that how well they work as they temperature increases but then at a certain point the enzymes are going nature so it's going to come quite steeply down and if it gets too hot the whole thing's gonna catch on fire very similar with the level of water is going to be slowly increasing as it gets wetter and then past a certain point the bacteria just are going to be able to cope they need to have oxygen they need to be able to respire and if there's too much water they just can't do that oxygen there is a very narrow amount of oxygen that they will be able to use without question they can't do anything and too much oxygen and then it starts through a common toxic in the garden godless can compost them so that I can get rid of that unwanted things I then take some nutrients the Giddy's in there and put them back onto the garden compost is gonna get rather hot as this goes on and it's gonna get worse Mellie and gas is going to be released this gas can be harvested and used when we are looking at food chains we can also think about constructing pyramids either parables the numbers or periods of biomass each of these are trophic levels and when we do numbers you just need to get the number of things that eat the thing below it and biomass we need to take a look at the number and the mass of this stuff that's being eaten as we drop seen trophic levels roughly 10% of energy is transferred from one to the other it is going to be lost in a number of different ways respiration waist as in urea and feces movement running around jumping doing normal animal things these security is how sure that we are going to have food on our tables how we sure we are that our supermarkets are going to be full of things for us to buy if as a country we don't produce much of our own food we have to buy it in from other places which means we depend on other countries other people's climates trade agreements with these other countries and transport arrangement getting the food across borders increasing our own food production in this country will ensure our food or help to ensure our food security if we are producing our own food we're not reliant on other people we need to take into account ways to increase yields for example using fertilizer but then will Sinise take him to come to impact that we're having the wider environment and we need to take into account production methods are they land intensive are they good for the environments or knots as well an island saleable fishing is one way we can helps in secure our food security but we need to take into account things like net size are we catching fish before they're too old for they've had chance to reproduce are we catching too many do you maybe need to move to linehalt this so we don't catch endangered species and we need to look at fisheries quotas we can also look at new ways to developing food for example culturing microorganisms which we can use as a food source

49 thoughts on “The Whole of AQA Biology Paper 2. B2. 9-1 GCSE science revision

  1. TIME STAMPS
    8:20 menstrual cycle

    12:29 meiosis + mitosis

    14:45 asexual reproduction

    15:29 genome

    21:25 embryo screening

    24:05 evolution

    27:10 speciation

    28:24 selective breeding

    33:09 Bacteria

    36:10 ecosystem

    38:50 plant adaptation

    39:32 good chain

    41:12 carbon cycle

    44:26 water cycle

    47:03 microorganisms Decay

    47:12 Biodiversity

    49:40 global warming

    51:52 Brain separates

  2. Really good video. Is there any way to get rid of the background noise on the video as it gives me a headache. Thanks though

  3. People are saying last minute gang from 12 hours ago… It's almost 7AM and I take the test at 9AM…

  4. I've been up since 2am trying to cram the whole paper 2. Question. Can I get a grade 7 or 8 from just watching this video?

  5. Okay, I love your videos but please I will buy you a new microphone omg its so bad at some points…

  6. i wanna do both bio and english lang for a level but none of this is getting in my head im done for bruv i gotta sleep

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