Transcript for:
Biology Lecture on Homeostasis and Human Physiology

hello lovelies in this video Lauren the head of biology has done a grade n explanation of the whole of your AQA paper to for you now she properly knows what she's talking about so this is a great video for you to make some flash cards from make some notes from then once you've done that you can jump down to description go over to website and then you can try do completely free questions completely free flashcards that we've made for you to make your revision a bit easier as well as the predicted papers that are long for this year and then the detailed walkthroughs that she's done to show you how she wants you to ask questions in the [Music] [Applause] [Music] exam homeostasis is the regulation of conditions to maintain an Optimum internal environment in response to either internal or external change there are three main things that homeostasis Works to control in humans body temperature which is should be around 37° in humans blood glucose concentration and water levels maintaining these is important so that enzymes and cells function properly in the body homostasis is controlled by the nervous system and the hormonal or endocrine system through the same cyclical processes so it starts with receptors they are found in organs that detect the changes in the internal or the external environment we call those changes the stimulus then they send information either via hormones or nervous impulses they send this information to coordinators which process the information this could be the brain or spinal cord in the nervous system or for example the pancreas in the hormonal system then the coordinator sends out hormones or nervous impulses to effectors effectors are organs which respond to the stimulus and these are always either glands in the hormonal system or muscles in the nervous system and then the body responds to whatever the change was or the stimulus was we need to be able to describe the structure and function of the nervous system the nervous system is made up of two main parts the central nervous system or CNS which is made up of the brain and the spinal cord and then the nerves which come out of the spinal cord which are bundles of nerve cells the nervous system works to allow humans to react to their surroundings and coordinate their responses nerves transmit electrical impulses to send information so this is the same sequence that we saw before in that cycle we're going to look at a specific example for the nervous system so A change is caused by a stimulus so something changes in the internal or external environment is detected by a receptor and that detects the stimulus and these receptors are normally found in sense organs which are part of the nervous system so your eyes your skin your nose your ears your mouth and your muscles which detect stretch they will send electrical impulses to the coordinator which is normally the central nervous system it could be the spinal cord or the brain they then send electrical impulses along nerves to the affector and this will be a muscle or a gland and the response will either be to release the hormone or to contract if it's a muscle and the response brings about the change in the body so for example if a muscle contracts something in the body could move so don't forget that between all of these from the receptor to the coordinator and from the coordinator to the affector there will be a nerve that will be sending the electrical impulse that is the information that's traveling between between these different organs we need to know specifically about a certain type of response called reflex action reflexes are special because they are unconscious so they do not involve the brain so you don't think about these actions they just happen they only involve three neurons and those so they are known as the reflex arc they are designed to keep the body safe from harm or injury there are only a few examples of true reflex actions the knee joke response your pupil response to light blinking if something comes near your eye or coughing and sneezing if you inhale some particles the other example is the example we've got here to look at in the diagram which is moving your hand or something part of your body away from pain so the stimulus here is that sharp pin is going to prick the skin this is detected by receptor in the skin which sends an electrical impulse along the sensory neuron the sensory neuron is always connected to a sense organ so that's how to remember it sensory neuron sense organ then that connects to a relay neuron which is found inside the coordinator which is the spinal cord in this case the brain is not coordinating the response because it's a reflex action and it needs to be really fast then the relay neuron sends an Impulse to the motor neuron which goes back out and connects to an affector so motor think motor like a car or movement it's connected to the affector which is often a muscle which contracts to cause movement so think motor move motor muscle so then the muscle is going to contract in order for you to move your arm or hand to pull your finger away from the pain so this is an example of a reflex arc using the three neurons they're always going to be in that order sensory neuron connected to a receptor relay neuron in the spinal cord motor neuron attached to an affector I've circled the gap between the relay neuron and the motor neuron as an example of a syapse this is the name for the gap between two neurons it's where a chemical is released which diffuses across the Gap and binds The receptors on the next neuron to trigger the electrical impulse so this is how one neuron triggers an electrical impulse in another neuron across this Gap by releasing a chemical that diffuses across finds The receptors and it starts the electrical impulse in the next neuron we need to know an example of how we can measure reaction time as part of a practical method so normally we use the ruler drop test but you can use the computer program as well so the ruler drop test is where you get a meter ruler and someone holds it above the thumb of the non-dominant hand of the participant so that's your left hand if you're right-handed for example the r is then dropped randomly and without any warning the participant has to catch the ruler as fast as they can and the distance that's closest to the top of the thumb which is where the zero on the ruler should have been at the start is recorded in centimet and then we use a table to convert that centimeter measurement into a reaction time in seconds there are many independent variables that you could change in this experiment that could affect reaction time so things like practice so how many times have you caught the ruler the more you do it the faster you should get the amount of sleep you've had whether or not you've had caffeine which should increase your reaction time distractions which can slow down reaction time and sex and age can also contribute as a factor the dependent variable what we are measuring is the distance the ruler Falls before being caught in centim and then obviously we can then convert that to reaction time but we're not measuring Reaction Time Direct ly like with a stop clock or anything because that would not be accurate because it would be measuring the person who's pushing the timer buttons reactions not the person who's catching the ruler things we can control in the experiment or should control to keep them the same the mass of the ruler is an acceptable answer because that can affect how fast it falls and how easy it is to catch but nothing else about the ruler you cannot get marks for saying things like the same ruler used the randomness of the drop so making sure you it's truly random every single time and making sure the start point of the ruler should be the same every time so you're not accidentally giving them a few centimeters obviously as well as those we should control anything else on that independent variable list that we are not changing so if we are just looking at whether sleep affects reaction time everything else should be kept as same as possible because they can affect the reaction time so we should make sure they've got no distractions they haven't had loads of PR ractice beforehand they haven't had caffeine or they've all had the same amount of caffeine and if possible similar ages and Sexes one key tip to remember for the exam is that slow reactions will mean a greater or higher value of time in seconds faster reactions equal smaller amounts of time people forget and see greater numbers and think that that means faster or better reactions that's not true for a fast reaction time you want a lower number the brain the brain is a complex organ that controls human behavior it is made of billions of interconnected neurons but it has different areas that are responsible for different functions and we need to be able to label them and say what they do the cerebral cortex controls conscious thoughts language memory intelligence these are known as the higher brain functions the cerebellum it coordinates muscle contractions and helps with balance and control of the body the medala oblongata controls unconscious behaviors like heart and breathing rate so these are things that you don't think about that you can't control by thinking they just happen automatically we need to be able to explain how the brain is studied and how brain disorders can be treated the brain has been investigated and mapped out by being able to study people who have brain damage or injury by identifying what their where their injury is and then figuring out what effect that has on their function we can identify what that part of the brain does they've also identified what parts of the brain do by electrically stimulating the brain or measuring electrical activ in the brain using a machine that's called an EEG MRI scans and other scans can be used to visualize the brain structure here's a picture of an MRI here there are ethical issues with studying people with brain damage that we have to think about like getting their consent for this type of study on their behavior the reason we need to use Imaging and electrical stimulation is because the brain is inside a skull so it's hard to access and to see how it works and treat it using these electrical techniques though has been able to help with diagnosing and treating certain disorders like epilepsy there are some other issues with diagnosing and treating issues with the brain it's a complex and delicate organ complex meaning that it's not fully understood yet so we don't know exactly what every part does and how and it's delicate which means it can be easily damaged during surgery it's hard to access as we said it was in the skull and nervous tissue is difficult to repair or replace there is also an issue that not all drugs are able to reach the brain due to special membranes that coat it the ey is a sense organ that contains receptors that can detect changes in light intensity or color the optic nerve transmits electrical impulses to the brain the retina contains light receptors which are rods and cones the Scara supports and protects the eye the iris these are actually muscles that control how much light enters the eye through the pupil which is the hole in the center the cornea this is a transparent layer that protects the pupil and helps to focus light the ciliary muscles and the suspensory ligaments work together to help to control the size and shape of the lens which I've labeled to focus light onto the retina the eye is two main roles to adapt to different light intensities in bright light the circular Iris muscles contract and the radial Iris muscles relax in dim light the circular Iris muscles relax and the radial Iris muscles contract so this makes the pupil smaller in bright light so less light enters the eye and larger in dim light so more light enters the eye the other function of the eye is to accommodate to focus light from near or far objects for nearby objects the ciliary muscles contract and the suspensory ligaments loosen this refracts the light more so that it focuses on the retina for Far Away objects the ciliary muscles relax and the suspensory ligaments tighten this refracts the light less to focus on the retina the change in refraction is due to the change in the size of the lens so for nearby objects it makes the lens thicker which causes more refraction and for Far Away objects it causes the lens to become thinner which causes less refraction there are two ID effects for you to know about hyperopia is one of them this is also known as long-sightedness it's where the lens is too flat so it can't refract the light enough and nearby objects appear blurry it's fixed with a convex lens in glasses or contact lenses which diverges the light rays myopia is where far away objects are blurry and it's also known as shortsightedness this is where the lens is too curved so it refracts the light too much it can be fixed with a concave lens in glasses or contact lenses which converges the light rays there are other treatment options for these defects such as laser eye surgery to change the cornea shape so that changes the cornea shape permanently to change the way it refracts the light so that you don't need lenses blurred division may also be caused by a cataract or a cloudy lens and you can have replacement surgery for the lens in that case temperature control in the body is regulated by the thermo regulatory Center in the brain this contains receptors that detect blood temperature skin receptors can also detect changes in temperature and they can send nervous impulses to the therm regulatory Center in the brain as well if the signal from these is that the body is too cold then changes will be made to increase the body temperature Vaso constriction where the Lumen of blood vessels near the skin Narrows to reduce blood flow muscle contraction or shivering which increases the respiration rate and hairs on your skin standing up to try and trap a layer of air and sweat stopping if the therm regulatory Senter detects the body is too hot changes will be made to lower the body temperature vasod dilation this time where blood vessels near the skin the Lumen widens to increase blood flow hairs on the skin lie flat and sweating increases sweating is useful because the heat energy is used to evaporate the sweat from the skin most of the activities when you are too cold help to reduce heat loss by radiation most of the changes when you are too hot help to increase heat loss through radiation the endocrine system is a system of glands that secrete hormones directly into the bloodstream the blood carries the hormones to target cells around the body where it has an effect we need to be a to compare this system to the nervous system and the way it works the hormone system uses chemicals not electrical impulses to send information the messages travel in the blood not through nerves the response is slower in terms of time for it to actually take an effect but it can affect multiple organs all at once we've got a labeled endocrine system here and you need to be able to label all of these on a diagram and also to know what hormones each of these glands produce the pituitary gland is found in the brain it's also known as the master gland because it releases hormones that act on other glands causing them to secrete more hormones the adrenal glands are found on top of the kidneys and they secrete adrenaline the pancreas secretes insulin and glucagon the ovary secretes estrogen and progesterone in females the test secrete testosterone in males and then we have the thyroid gland which is in the neck and that secretes thyroxine the pituitary gland secretes two hormones that are also involved in the menstrual cycle these are FSH and LH controlling blood glucose blood glucose levels are monitored and controlled by the pancreas when blood glucose increases after a meal is digested the pancreas releases the hormone insulin this is an example of what we call negative feedback because the change that happens in the body is reversed through this process so it starts with receptors in the pancreas detecting the increase in blood glucose levels the pancreas is also the coordinator because it releases the hormone insulin in response to this the insulin is the hormone that then travels in the bloodstream insulin binds to the liver which is the affector and it makes them absorb glucose from the blood into their cells the response then is that blood glucose levels decrease because excess glucose in liver and muscle cells is then converted to glycogen for storage controlling blood glucose also works in the other direction so when blood glucose levels drop too low for example after exercise the pancreas releases the hormone glucagon this time this causes cells to break down glycogen and release the glucose into the blood so this time receptors in the pancreas detect a decrease in blood glucose levels the pancreas releases the hormone glucagon the glucagon hormone then travels in the blood to the liver it binds to the liver cells and makes them release glucose into the blood they do that by breaking down stores of glycogen to release glucose and the response is then that the blood glucose level increases this with insulin forms a negative feedback cycle so both the hormones insulin glucon will go up and down in response to blood glucose levels and it keeps the blood glucose levels stable around the optimum diabetes is caused when the blood glucose levels are not being controlled properly it can cause high blood glucose levels there are two types type 1 diabetes is when there's not enough insulin or no insulin produced by the pancreas the treatment is insulin injections to help lower blood glucose type 2 diabetes is when insulin receptors on target cells like the liver and muscles do not respond to insulin being made by the pancreas anymore treatment is a low carbohydrate diet and exercise sometimes if this is unsuccessful glucose lowering medication can be taken but insulin is not an appropriate treatment obesity is a risk factor for type 2 diabetes maintaining water and nitrogen balance so we need to help to understand why it's important to maintain our water levels in the body is because the water levels in the body need to be the same as the cell cytoplasma so the amount of water in the liquid in the blood plasma and tissue fluids surrounding the cells needs to be the same to prevent osmosis because if water moves out of cells like red blood cells here for example then the cell will shrink if water moves into red blood cells or other cells then they could burst okay so obviously if it shrinks or bursts that can severely damage the cell and prevent its function excess water ions and toxic substances like carbon dioxide and Ura have to be removed from the body through the process of excretion there are three main ways that water ions and Ura are removed water ions and Ura are lost from skin in sweat when it evaporates water is also lost as water vapor or gas when we exhale excess water ions and Ura are removed by the kidneys into urine and the urine is obviously then excreted from the body through the bladder there is no actual control about how much water is lost through sweat or exhaling or breathing out but there is control over how much water leaves the body in urine and it's controlled by hormones as we said this is important because if cells gain or lose too much water then they won't function properly how do we get rid of excess nitrogen so remember that proteins can be broken down in the body to form amino acids and amino acids contain nitrogen so these are ones that cannot be stored in the body because we can't store nitrogen containing compounds safely the excess amino acids so any amino acids that are extra that we do not need to make any more proteins in the body travel to the liver and at the liver they are deaminated and so they are removing an amino group from the amino acids and that converts them into ammonia but this is quite toxic so we have to convert the ammonia again into less toxic substance called Ura the kidneys filter Ura from the blood and it's excreted as urine from the bladder so the kidneys filter the Ura out of the blood it gets mixed with water and then leaves the body as urine so blood enters the kidneys that contains Ura and then blood will leave the capillaries that doesn't contain Ura so it filters out any of the substances including Ura and any excess ions that we don't need that will then leave the body in the urine but the cleaned blood or filtered blood is then set back to the heart to be sent back around the body again the kidneys form the urinary system with the bladder they filter the blood to remove Ura water and excess ISS which leave the body in urine the kidney contains thousands of fine tubules which filter the blood and then reabsorb useful substances such as glucose some ions and some water this is known as selective reabsorption the contents of urine can indicate if the kidneys are functioning properly so for example if things like glucose and some ions which should be being reabsorbed are present in the urine that can indicate that selective reabsorption is not happening properly if the kidneys fail to work properly there will be a buildup of toxic Ura in the body as well there are two treatment options for kidney failure dialysis this is where a patient is attached to a machine which removes blood from the body and filters it Ura is removed from the blood and then the blood that is clean is returned to the body dialysis fluid flows next to blood in an opposite direction in the machine and it causes diffusion of Ura and excess ions out of the blood and into the dialysis fluid no glucose is removed because the dialysis fluid contains glucose this makes sure that glucose stays in the blood for respiration and the dialysis membrane between the blood and the fluid is semi-permeable just like a cell membrane the other option is a kidney transplant this is where a kidney would be received from a dead or a living donor because you can live with only one kidney and everybody has two they have to be a tissue or blood type match to try and reduce the chance of rejection the benefits of dialysis are that they're being used to keep people alive while they wait for a kidney transplant but it's not a long-term solution people can feel really unwell between trips to the hospital and it can be really inconvenient to go and sit at the hospital for hours every few days the Downs signs of having a kidney transplant is obviously there is a shortage of donors so it may be a while to wait for one and it will also require them to take immunosuppressant drugs for the rest of their life to prevent the organ from being rejected but a transplant is a long-term solution as soon as the transplant has taken place the person will still feel better and they will not have kidney failure anymore unlike water being lost from the lungs or skin the volume of water lost in urine is controlled by hormones to make sure the water levels in the body remain around the optimum it's controlled by the pituitary gland which secretes the hormone ADH or anti-diuretic hormone this process is another example of negative feedback so receptors in the pituitary gland detect high blood water levels so there's too much water in the blood the pituitary gland releases less ADH into the blood this means that less water is reabsorbed into the blood so more water is removed in urine and this causes blood water level to decrease and it lowers it back to the optimum in the other direction if receptors detect low blood water levels or too little water in the blood the pituitary gland will release more ADH into the blood and then more water is reabsorbed into the blood so less water will be removed in the urine and this causes the blood water level to return up to the optimum so it increases so a little summary to help you remember less ADH means more water in urine means there's a greater volume of urine leaving the body so you will we more if there's more ADH there'll be less water in the urine so there'll be a smaller volume of water leaving the body in urine so you will we less during puberty in humans reproductive hormones are released which cause the development of secondary sexual characteristics this cause physical changes in the body that prepare the body for sexual reproduction the testes release testosterone which causes sperm production the male ganet to be produced the pituitary gland in the brain releases LH and FSH FSH or follicle stimulating hormone causes an egg to mature in the ovary and L or lutenizing hormone causes an egg to be released from the ovary the ovary releases estrogen and progesterone which build and maintain the uterus lining these hormones from the ovaries and the pituitary gland control the menstrual cycle we need to know that the menstrual cycle is a roughly 28 day cycle and at day 14 roughly halfway through the cycle an egg is released from the ovary and this is known as ovulation if that egg is fertilized then it will implant into the wall of the uterus and the person will become pregnant if not and there is no sperm to fertilize the egg then the uterus lining and the unfertilized egg cell will fall away from the inside of the uterus wall this is known as menstration or the period the four hormones that we've mentioned FSH LH estrogen and progesterone interact with each other to help control the menstrual cycle for example increasing estrogen concentration increases LH production so this is to make sure that an egg is only released when the uterus lining is ready to receive it increasing progesterone from the ovaries inhibits FSH and LH production this makes sense because it prevents any other eggs maturing or being released during a pregnancy or potential pregnancy FSH and estrogen interact through a process of negative feedback so increasing FSH causes an increase in estrogen production but then increasing estrogen production inhibits FSH this is to make sure that as an egg is maturing in the ovary the uterus lining begins to develop through the estrogen increase but what we need to make sure is that when we increase our estrogen levels of we're ready to receive an egg only one egg matures in a cycle so we inhibit FSH to prevent any other eggs maturing we also need to understand that the decrease in progesterone towards the end of the cycle just before menstruation is what causes menstration so when that progesterone level decreases the lining of the uterus is no longer being maintained which is why it breaks away and leaves the body through the vagina as the period if someone was able to be have the egg fertilized and become pregnant within this time and progesterone levels were high to maintain the lining then the progesterone levels would be kept High throughout the pregnancy to maintain that uterus lining to help the developing fetus and to protect it contraception is any method used to try and prevent pregnancy it's a form of control infertility which is the ability to have children there are two types or groups contraceptives hormonal and non- hormonal or barrier methods the hormonal examples include the pill the patch or the implant and some ruds they contain progesterone and estrogen to inhibit FSH and LH so no eggs mature or are released from the ovaries so they can't be fertilized by sperm cell one example of non- hormonal barrier methods is the condom or any other physical barrier that stops sperm reaching eggs the benefit of condoms is that they also provide STI protection spermicidal products can kill or disable the sperm so that they cannot swim to the egg an IUD is placed inside the uterus to prevent an embryo from implanting in the wall they can be copper or plastic or they can be hormonal as as well so an IUD could potentially be in either of these groups and finally surgical sterilization is a permanent solution to cut the tubes that release gametes so to cut the Fallopian tubes so that eggs cannot leave the embryo and reach the uterus and also to cut the tubes that attach to the testes so sperm cannot be released either we need to be able to evaluate these me methods so obviously the benefits of condoms are that they provide the STI protection and nothing else does for most non-h hormonal methods that they don't provide side effects which is a good thing and they're often very effective there can be some disadvantages with the iug for example it can cause pain it can cause bleeding there is a risk of infection because you're inserting a foreign object into the body and they can also change your periods as well making them heavier or more painful but they are long-term solution for contraception hormonal methods have quite a few negatives because they can obviously have side effects they can affect periods making them heavier or longer or more painful they can also cause things like headaches and risk of things like blood clots and again there is no STI protection with these but they can be long-term so things like the implant or iuds can be in place for years so it's not something that you have to take every day remember as a tablet or anything like that so that can sometimes be a good solution and they can obviously be reversible um because when you stop taking them your body should go back to normal hormones can also be used to treat infertility this is the inability to have children naturally fertility drugs including FSH and LH can be injected to increase egg maturation and release this may be all that's needed to help a woman fall pregnant if these hormones are low or is not releasing or maturing enough eggs every cycle this can all that's be needed in order to encourage that to happen to make sure that fertilization can occur naturally if this doesn't work then the second option is IVF or invitro fertilization eggs are collected and sperm collected the way eggs are collected is the similar way they would have to inject the FSH and LH drugs to increase the number of eggs being maturing and released from the ovary and then they are collected and then sperm is collected these are encouraged to fertilize in the lab in a dish or in a test tube which is where the name comes from inv vitro literally means in the glass and so once fertilization has occurred then they are left to develop to form an embryo and then those embryos can be replaced back into the uterus in order to create a pregnancy we need to be able to evaluate the process of IA so obviously the main advantage is that it allows parents to have a biological child where otherwise they may not have been able to do that or they would have struggled to do that naturally the negatives are that it's very physically and emotionally stressful particularly for the mother involved there is no higher success rate than normal so there is no increased chance that you will get pregnant with this method whether or not the embryo implants into the uterus wall and forms a pregnancy is the same chance as if fertilization had happened in a uterus naturally it can also lead to multiple births so Twins or more so quadruplets triplets Etc and that is dangerous for both the babies and the mother there is also an element that any unused embryos that have been fertilized within the lab that are not used so if one or two were implanted and a baby is born and the parents no longer want the embryos that they created through IVF then they would be destroyed and this carries the same ethical issues that we looked at with embryos being used for stem cell research we need to be able to explain the action of the hormone thyroxine thyroxine is secreted from the thyroid gland which is in the net thyroxine controls the basal metabolic rate which is important for growth and development thyroxine is controlled by negative feedback loop so the pituitary gland releases a hormone called thyroid stimulating hormone into the blood this then travels to the thyroid gland and it causes the thyroid gland to release thyroxine into the blood when thyroxine levels in the blood become too high this actually inhibits the release of TSH from the pituitary gland which causes them to decrease again and then once they decrease the inhibition of the ATU gland stops and then it will release TSH again when thyroxine levels drop too low receptors in the pituitary gland control how much thyroxin is released to change the metabolic rate under certain circumstances one example is when the body temperature decreases the py gland receptors detect this and release more TSH in order to increase thyroxine released into the blood and this increases the metabolic rate increasing the metabolic rate increases the rate of respiration to release heat energy in order to help increase the body temperature another time when the pituitary gland will affect the thyroxine production is when stress levels increase increasing stress levels cause the pituitary gland to release less TSH which means less thyroxine is released and the metabolic rate is slowed down this reduces the rate of respiration so more nutrients are stored as fat the idea behind this is an evolutionary one so when we are suffering from times of stress the body thinks we are going to need extra fat reserves or energy reserves in case something bad happens and maybe we don't have ACC access to food so it's to try and help the body survive any long-term changes by having energy stores as fat now obviously this is slightly inconvenient and it's why having high stress levels can cause weight gain the adrenal glands release adrenaline adrenaline is released in times of fear or stress to prepare the body for flight or fight to respond to the environmental change or whatever is causing fear or stress it has different actions on different organs in the body it reduces blood flow so the digestive system in order to make sure that blood is sent to more important organs it increases heart rate and it increases breathing rate this is to make sure that more oxygen and glucose gets to important organs including the brain and muscles this is important so that your brain can think and react to surroundings and that your muscles are able to contract in order to allow you to run or fight to survive this hormonal mechanism is not an example of negative feedback because when the danger or the fear or the stress passes the adrenaline release will stop and then all of these symptoms will stop as well so there is nothing causing a negative feedback loop here it's just you either are secreting adrenaline or you are not plants produce hormones to control and coordinate growth and responses to light and gravity light responses are known as photo tropisms and gravity responses are known as Geo or gravit tropisms Orin is the hormone or group of hormones that controls these responses to the light and gravity unequal distribution of oxin in Roots and choots causes unequal growth first let's look at phototropism phototropism is a positive response in shoots that means they Bend towards the light this can be explained by more Orin gathering on the Shaded side of the Chute which causes increased cell number by increasing cell elongation and growth that causes the Chute to bend towards the light in Roots the phototropic response is negative because Roots Bend away from the light this time more Orin still develops on the Shaded side but Orin inhibits growth and Stell elongation in Roots we need to know how to investigate phototropism and that's responses mostly this can be done by covering different parts of the choot with foil so the tip the center of the shoe or cutting or removing of the tip and then having light coming from from one direction to see if the shoots Bend towards the light you can measure both the growth and the direction of the shoots in a certain amount of time as well as repeating the experiment plenty of times with lots of different seedlings so that you can take good averages you should also make sure to keep all other conditions that could affect the growth of the shets the same so temperature water the amount of nutrients all of these need to be controlled if they could potentially affect the growth of the plant in the experiment so the only Factor we should be changing is where light is hitting the Chet Geo or gravitropism is negative in shoots because they grow against the pull of gravity this makes sense because there's more chance of them being able to find light which they need for photosynthesis if they grow upwards Towards the Sky a similar response Oren moves to the Lower Side of the sh causing more cell elongation so the Chute bends upwards geotropism is positive in Roots because it grows with the pull of gravity so they grow down and into the soil for support and also to help the plant find water deoxy moves to the Lower Side inhibiting cell elongation so the upper side grows more or cell elongate more and therefore it causes the roote to bend downwards we also need to be able to know how we could investigate geotropic responses in Plants the main thing here is to exclude light so if you just want to measure the effects of gravity you need to make sure it's done in complete darkness so we know that light isn't having any effect you could grow seedlings in dishes at different angles vertical upside down in order to show the different effects of gravity You' then let them grow for a certain amount of time and record the direction of the Chute and root growth just as with phototropism all other conditions that could affect the growth of the plants need to be kept the same temperature water nutrients all of those obviously not anything to do with light other than the fact that it's completely dark plant hormones can be used by humans to control plant growth in agriculture and horiculture orins can be used as weed killers because they cause plants to grow too fast and collapse they can be used as rooting powders for cuting which is what you can see in the picture above and they can also be used to promote growth in tissue culture so they can be used in the AAR gel when we clone small plants imp plants ethine controls cell division and fruit ripening humans use it in the food industry to control ripening to help with transport and storage so it means that fruit can be transported unripened where it is more hard and therefore less likely to be damaged by transport and storage and then Ethan can be added to ripen these fruits and vegetables when they arrive at Shops ready to be sold imp plants J initiate seed germination gibberellins can be used by humans to end seed dormy in other words trigger seed germination promote flowering in plants and increase fruit size [Music] [Music] [Music] [Music] sexual reproduction involves the fusion of male and female gametes that are produced by meosis so we have eggs and sperm in humans as the female gamut is an egg and the male gam is the sperm in a plant the female gami is also an egg and it's also produced by meiosis in the ovaries the same as in humans and then the male gamet is pollen and this is produced by meiosis in the anthers the male gam of sperm in humans is produced in the testes sexual reproduction mixes different DNA from each parent creating variation in their offspring ganet are non-identical and the fusion of each pair of ganet so which sperm and which egg meet each time they fuse is random so this helps to shuffle and mix the DNA to make sure that every Offspring is genetically unique asexual reproduction is carried out by all bacteria some plants and a few animals this example diagram is bacteria dividing by binary fishion which is very similar to mitosis no gametes are involved in asexual reproduction there is only one parent cell not two there is no mixing of DNA so there is no genetic variation in The Offspring they are all identical it relies on mitosis instead of meiosis to produce genetically identical clones of the parent my is is the type of cell division that produces gametes or sex cells it occurs in reproductive organs for example testes and ovaries in humans to start with we have a normal body cell that is diploid or has the full number of chromosomes that a normal body cell would have in this example you can see four chromosomes then the DNA replicates or doubles or copies itself to prepare for cell division so now we have eight chromosomes at this point this is exactly the same as the start of mitosis then we have our first cell division where that cell splits into two so each cell now has four chromosomes again then each of those cells splits into two again so we have our second cell Division and this produces four non-identical cells with half the number of chromosomes in this case two of the original parent cell we call these cells haid so diploid cells have the full number of chromosomes of every cell in the body and haid have half the number of those chromosomes the reason these four cells are nonidentical is that during meosis the DNA is shuffled in order to make sure that each of these gametes will be unique we need to be able to compare meiosis and mitosis so unlike mitosis there are two divisions not one there are four cells produced not two and the four cells produced are non-identical and they are haid or contain half the number of chromosomes let's look at what happens and why meiosis is important producing these gametes once they are ready to be used in sexual reproduction so now we are looking at two human gametes an egg cell the female gami with 23 chromosomes which is half the number of the normal body chromosome number in humans and sperm cells have 23 chromosomes as well in their nucleus during fertilization the nuclei of each gami fuses and the full number of chromosomes is then restored to form a diploid zygote which is the new cell that's going to form the new organism and that will now have all the 46 chromosomes it needs in order to carry on developing and growing into a human that single cell will start to divide by mitosis to form identical copies of itself to create an embryo which is a ball of stem cells and then those stem cells keep dividing by mitosis to increase the cell number but they also go through the process of differentiation to produce all the different specialized cells needed to make a fetus it's important that we understand the role of meiosis and mitosis so we need meiosis to make the gametes that have half the number of chromosomes so that the DNA can be mixed when the two fuse together during fertilization to create a cell that has the full number of chromosomes we need for a body cell and then we need mitosis to multiply that cell number making identical copies in order for a fetus to grow and we need those cells to go through differentiation to become specialized to form all the specialized cells and tissues in the body some organisms can reproduce both sexually and asexually depending on their environmental conditions plants can reproduce sexually using using flowers to make seeds they can also reproduce asexually using Runners like this strawberry here where a new stem comes out grows into the ground and forms roots and a new stem of its own to form a new identical plant or things like bulbs like carrots potatoes or onions that grow structures underground that can then be split divided and create new identical plants protests for example the area causing parasite can reproduce asexually in human liver and blood cells but then reproduce sexually in the life cycle phase that happens inside the mosquito Vector fungi can reproduce sexually to create genetic variation it can also reproduce a seually by budding off identical spores this is for example what we saw when we looked at Rose black spot the fungal pathogen that produces spores that can then spread to other plants we need to be able to evaluate these two types of reproduction a positive of asexual reproduction is that it only needs one parent so it is faster and it requires less energy a disadvantage then of sexual reproduction is the opposite because you need to find a mate because two parents are needed this means it is slower and it uses up more energy a positive of sexual reproduction is that allows natural selection to occur if the environment changes because genetic variation means that some Offspring might be more likely to survive so it allows natural selection or the process of evolution to occur a disadvantage then of asexual reproduction is there is no genetic variation in Offspring so they are less likely to be able to survive environmental changes for example a new pathog a positive of sexual reproduction for humans and our benefit is that it allows humans to selectively breed organisms for desired characteristics so it allows us to speed up natural selection for example in crop plants and livestock animals to improve our food production an advantage of aexual reproduction for some organisms is that they can produce many identical Offspring when condition are favorable this is also an advantage to humans because it means that we can easily produce large numbers of plants for sale or to grow as food very quickly we need to be able to know how DNA is organized and the size difference between these features so I have a cell which is the biggest thing here inside the cell is my nucleus inside the nucleus are the structures called chromosomes which are made up of coiled DNA DNA is a polymer made up of two strands that is Twisted to form what we call a double helix you can see that Twisted structure here short sections of DNA are called genes and these code for proteins this is because the DNA code on the genes codes for a particular sequence of amino acids that when join together form a protein The genome is all the genetic material in an organism the Human Genome Project was completed in 2003 to completely sequence and read the human genome it's been really important to allow us to do a particular set of things we can use it to search for genes that are linked to different diseases this could help us to diagnose patients we can use it to understand and treat inherited genetic disorders and we've been able to use it to trace human migration patterns from the past through the process of human evolution DNA is a polymer made up of two strands and four different nucleotide monomers can be joined together to make up these two strands you can see a labeled diagram of a nucleotide here they all contain a phosphate group a sugar and a base there are four different bases represented by the four letters a c g and T I've labeled the bases on the two strands of DNA that you can see here a sequence of three bases codes for a particular amino acid for example cgt will code for the amino acid alanine therefore the order of bases in the DNA code or on the DNA chain controls the order of Mino acids that will then be joined together to make a particular protein when this sequence is read in order this is how we say and this is why we say DNA codes for proteins So reading the code of letters will tell the order of the amino acids that you need to put together to make a certain protein a template copy of the DNA sequence of a gene will leave the nucleus and travel to a ribosome in order to produce a protein ribosomes are the site of protein synthesis carum molecules arrive at the ribosome bringing specific amino acids to build the protein chain in the right order bases pair with their complimentary base a always pairs with t and c always pairs with G if the DNA sequence is changed then the order of the amino acids in the protein may change after the protein chain is formed it is folded to produce a unique shape the shape is specific to the protein's function either as an enzyme or hor hormone an antibody or a structural protein like collagen if the amino acid sequences changed then a different shape protein could form mutations are changes to the DNA base sequence mutations occur continuously and most do not alter proteins or only affect them slightly but do not change their shape or function very rarely a mutation will code for an altered protein shape for example if an enzyme has a different shaped active site it can no longer bind to its substrate therefore its function has been affected by this mutation not all parts of DNA code for proteins non-coding parts of DNA control gene expression instead by switching other Gene gen on or off so depending on whether a mutation is in a non-coding or coding part of DNA will depend on the effect that it has so in if a mutation occurs in a non-coding piece of DNA then it could affect the expression of another Gene if the mutation happens in a piece of DNA that is coding for a protein then it could affect the shape and therefore function of the protein a gene is a short section of DNA that codes for a protein an alel is a different version of a gene that gives a certain characteristic the genotype is the alals an organism has for a particular Gene the phenotype is the observable characteristics that an organism has based on their genotype there are three three main genotypes homozygous recessive this means you have two lowercase letters to represent your alals because both alals in this genotype are recessive recessive alals need two copies in order to be expressed in the phenotype so for example here the phenotype will be white flowers because both of these Ali are recessive and they both code for white petals homozygous dominant is a genotype where both Al are dominant alals dominant alals are presented in the phenotype when there is only one copy of them so you only need one Al to be dominant in the genotype for that phenotype to be expressed then there are heterozygous genotypes this is where we have one dominant and one recessive alel or two different Al both in this case the heterozygous and the homozygous dominant genotype will produce the same phenotype which is red flowers in this case because both of these genotypes have at least one dominant Al for red flowers we can use Planet squares to predict the possible genotypes and phenotypes of The Offspring of two parents so let's look at an example where we have crossed two hetro zous red flower plants so they're both heterozygous so their Al need to be one dominant and one recessive and then we put these into the planet Square to show what the gamet alals could be so each plant could either give a dominant Al Big R or a recessive alel little r into their gamits and remember the gametes would be the eggs and the pollen in this case as they are plants we then fill in the pet Square by going down and across for each box to fill in from the gamet what they would receive from the parent and put them together so this gives us our possible Offspring genotypes so we have one homozygous dominant with two Capital RS two heterozygous Offspring with one capital r and one lowercase R and one homozygous recessive Offspring with two lowercase RS then we can work out the phenotypes so I've put the red and white flowers on to show you but obviously anything that has at least one capital letter or one dominant Al will have a red flower phenotype and then the two recessive Al for the little RS they will have the white flower phenotype we can either use ratios to describe the phenotypes so for example 3 to one red to white or we could use percentages to look at the probability of The Offspring being a certain genotype for example we can say there's 25% chance that The Offspring will be homozygous recessive when doing this in the exam question you should always annotate the pet Square to show what you mean so if I'm saying there's 25% chance of being homozygous recessive I Circle that Offspring genotype on my planet Square inherited disorders are caused by mutations in certain alals which are then pass down from parents to offspring a recessive inherited disorder example is cystic fibrosis is caused by recessive alel this means you need to have two copies of the recessive alel in order to actually have the disorder people who are heterozygous in their genotype are carriers so they can carry the Gene and the alel that causes the disorder but they won't have it themselves there's no cure for genetic disorders but cystic fibrosis could be treated with antibiotics to help the chest infections potentially an organ transplant later in life and even gene therapy where we potentially try to correct the 4y gene in certain organs in the body but this will not be a long-term cure just to help ease the symptoms temporarily a dominant inherited disorder example is polydactyl this gives extra fingers and toes it's caused by a dominant aliel so you only need one copy in order to have the disorder and there are no carriers because the heterozygous genotype people will have polya because they have at least one copy of the dominant Al this example is not a really serious ious Disorder so it's treated with surgery to remove the extra fingers and toes if the person wants to but there are other more serious dominant genetic disorders like huntingtons that can be life limiting we need to be able to read family trees that show the inheritance of these disorders through generations here we can see that this must be a recessive disorder because H and I have had a child L that has the disorder but neither H or I actually has the disorder themselves so they must be heterozygous and they must be carriers I would suggest putting letters on these family trees like this to represent the AL to help you figure out who has what Al or who must have what alals in order to be able to pass on those Al to their offspring so for example we know that b must also be a heterozygous carrier because a has the disorder so they have two lowercase recessive alals and in order for f to have inherited two lowercase recessive alos then they must have got one from B this can be used to help make decisions like if H and I would like another child but they would like them to be healthy and not pass on the Ali for their genetic disorder they could go through something which is called embryo screening embryo screening is done in a very similar way to IVF so IVF forms an embryo and then at the E cell stage of the embryo a cell will be removed for genetic testing so the DNA is analyzed and they look to see if that embryo has the inherited recessive alel in this example and then they'll make sure that only embryos without the disorder so without the genes that caused the disorder would be reimplanted into the uterus to guarantee a healthy child we need to be able to evaluate things like embryo screening the pros are that it helps parents to have a healthy child and it reduces suffering and obviously reduces the impact of an unhealthy child that would need lifelong treatment but the issues are similar to what we looked at with stem cells and IVF there are issues surrounding the destruction of embryos and ethics with interfering in the order of things in terms of naturally reproducing in humans there are 23 pairs of chromosomes 22 are body chromosomes and pair 23 are the sex chromosomes you either have XY or XX and these sex chromosomes play a role in determining sexual characteristics every time a sperm and an egg fuse in fertilization there is a 50% chance that the embryo made will be either male or female we can show this with a punet sare egg alals can only be xx and sperm alals could either be X or Y there is two out of four or 50% chance of getting an XX combination which will produce a female and there is two out of four or 50% chance of getting an XY combination of chromosomes which will be a male in most populations there is variation which just means differences in characteristics between organisms genetic variation is caused by mutation most of the time this has no effect on the phenotype but sometimes it can change it for example a new Ali for fur color in my cats could have been caused by a mutation variation can be the result of inherited genes the environment or a combination of both some examples of different characteristics caused by inherited genes are eye color blood type and Earl shape some examples of varied characteristics caused by the environment only are scars the language you speak and your hair length if you get it cut and there are two or three characteristics we can talk about being affected by both genetics and the environment so height and body mass although there is some element of genetic effect on these in your characteristics both can also be affected by things like Diet nutrition and exercise or things like light intensity or mineral availability if it's a plant and then flexibility is another example so yes genetically you could be more flexible than someone else but there is also the ability to improve your flexibility through practice evolution is the change inherited characteristics of a population over time it happens through the process of natural selection natural selection is where only some organisms with certain characteristics can survive in order to reproduce over time this makes them well adapted to survive in their environment and here you can see the tree of life this idea that shows that all of these species are connected to a single living common ancestor from billions of years ago we need to be able to describe the process of natural selection there's variation of population due to random mutation in my example here I've got a population with three different phenotypes a b and c which would have been caused by mutation some organisms have characteristics that enable them to survive and reproduce so we've got two changes that happen over time and in each one of those one of these phenotypes does not survive and the others go on to be able to survive and therefore reproduce they pass on Ali for these characteristics to their off spring so then there are more of those Ali and more of that phenotype in the population so you can see how over time the amount of phenotype C in the population increases until that's the only phenotype so over time this leads to populations having phenotypes that are best adapted to their environment if this happens in two populations of the same species they can become so different and adapted to different environmental conditions that they're phenotypes mean they're so different they can no longer breed together to produce fertile offspring which means they produced two new species this last point is an add-on but for the first four bullet points these are the exact language and the exact wording we should use when describing the process of evolution by natural selection in the exam humans have been breeding organisms for certain desired characteristics for thousands of years especially in crop plants plants livestock and domesticated animals the start of the process is that you would select two parents that have the desired characteristics you would then breed these together then select individuals again from The Offspring with the desired characteristics and breed these together so select breed select breed and then it's just about repeating that over many generations until all of The Offspring or you have many organisms that have the desired characteristics that you want we need to know some examples of the different desired characteristics that humans have bred things for in both animals and plants so in animals they have been bred for more meat milk egg or wool yield if we're thinking about livestock animals like cows sheep pigs and chickens also a gentle nature in domestic dogs so our dogs are our kind of pets and they have this kind of gentle calm loving nature that we have bread into them in Plants it's disease resistance in food crops and large or unusual or heavily scented flowers so there's loads of different flowers grown for aesthetic reasons because they look nice like orchids and they have been selectively bred there are some issues with selective breeding inbreeding reduces genetic variation and makes organisms more likely to suffer with recessive genetic disorders it's also more likely that they will be susceptible to new pathogens and other diseases because again they have very little chance of having resistance because they have low genetic variation genetic engineering involves cutting a gene out of a chromosome and transferring it to the cells of a different organism to give it a desired characteristic some examples are crop plants that have been modified to make them resistant to pests diseases herbicides or for a greater yield they can also have improved nutritional value like gold and rice bacteria have been modified to produce useful substances for example human insulin to treat type 1 diabetes we need to be able to evaluate the benefits and disadvantages of genetically modified crops there is a concern that any Gene in Plants could spread to Wild populations that means that they could also affect food chains by killing insects for example or biodiversity there's a concern they could cause allergic reactions in humans if eaten and people are concerned that there's been no long-term studies on the effects of eating genetically modified crops there are also some ethical concerns around genetic modification some people believe it's not natural to interfere with genomes and there are concerns of use over this technology in humans which is currently illegal we need to be able to describe the steps in the process of genetic engineering firstly the gene is isolated by being cut out of the chromosome that it lives in in an organism by using restriction enzymes the gene is then inserted into a vector to transfer to the organism a vector in this case is just a way of transferring the gene from one organism to another it could be a plasmid or a virus the gene is then transferred into the cells of the organism and then when the cells divide or replicate they will should all contain the new Gene so in this example we've genetically modified a bacterium with a plasmid and all those bacteria will now produce the protein encoded by the gene on the plasmid which could be for example human insulin when genetically modifying animal and plant cells they must be modified at an early stage of their development so as they grow and develop the characteristic will be in all of the organism because the gene should be in most cells that will divide this is easy with a small plant or a cloned plant with animals it would have to happen at the embryonic stage this is currently illegal in animals especially humans there are four different types of cloning one type of plant cloning is tissue culture this is where small groups of cells from a part of a plant are grown into new identical plants so a small piece is cut off it's grown on a nutrient agar and then that plant when it starts to divide into a few cells is then split apart in order to grow many different identical plants just from a few cells this type of plant cloning allows us to save rare plant species and can be used to grow many identical plants really quickly and this could be for sale a cutting method is an older or simpler method that's been used by gardeners for hundreds of years to produce new identical plants from one parent so a piece of the stem with some leaves is removed dipped into hormones in order to encourage rooting and then each one of those off Cuts will then grow into a new plant now on to animal cloning embryo transplants is where an embryo is left to divide into a few cells and then it is split before it starts to specialize and then each of the new embryos that's formed can be transplanted into a different host mother adult cell cloning this is where we remove a nucleus from the body cell of the animal to be cloned so we have its DNA and then we take an enucleated embryo from a different organism the embryo is then created by combining these two with an electric shock and then it's placed into the uterus of a new female that will then give birth to a clone of the original organism that we took the nucleus from at the start there are some ethical issues with animal cloning and people obviously disagree with you know interfering with animals in this way it can be that the animals can be unhealthier um the cloned animals that you get at the end and obviously there is low genetic variation in a population that includes cloned animals because they don't have any differences between them as opposed to when they produced through selective breeding or natural selection the theory of evolution occurring by natural selection was developed over time from information gathered by many scientists in 1809 lar theorized that characteristics changed during an organism's lifetime that were more useful or that were used more and so they grew or became stronger and then these characteristics were inherited by the next generation an example was giraff necks he believed that the gra giraffe necks grew during their lifetime as they stretched and reached upwards to eat food higher up in the trees and so then the long neck of those giraffes were pass onto their Rock spr we now know that this isn't true and this isn't how genetics works because we have to have mutations during lifetime but these could be passed on in 1839 and then in 1859 Darwin came up with this theory of natural selection after observation experiments fossils and discussion with lots of other scientists we came up with three key observations organisms within a species vary in phenotype some individuals with certain characteristics are more likely to survive than others the characteristics that enable these organism to survive are passed on to the next Generation he was initially hesitant about publishing these ideas in 1858 Wallace came up with natural selection Theory independently of darwi through his own observations and travels and discussions he communicated with Darwin who realized that he'd come up with it as well and so it kind of forced them to jointly publish their findings wace also worked on developing the theory of speciation so taking this idea idea of natural selection a little bit further to show how isolated populations of the same species can become new species through the process of natural selection darwi eventually published his findings in his book called On the Origin of Species in 1859 but there was lots of controversy about his new ideas this was because they challenged the belief that at the time God created all living things and that humans had always been on Earth there was little other evidence at time to convince other scientists for example there was not enough fossil evidence yet and there was no knowledge of antibiotic resistance the mechanisms of inheritance and genes that we know now wasn't known until about 50 years after his work was published Alfred Russell rollace worked a lot on the theories of speciation and since then we've worked on it more and now we understand there are different types of speciation speciation is when two or more species can be formed from an original population there has to be a method of isolation which prevents breeding in individuals between the populations here is an example with some lizards the population becomes geographically separated this isolation prevents breeding and mixing of genes between the two populations different random mutations will occur in each creating new phenotypes natural selection occurs due to the differ of environments so for example you can see on one side of the mountain there are no trees and on one side there are trees so that could be different environment different habitats different food sources which means that different adaptations will be better suited to type of environment they evolve differently through the process of natural selection until they can no longer into breed and then a new species is formed our understanding of genetics has developed over time with the work of many scientists in the mid 19th century mendal bread plants and observed characteristics that he called units were inherited from parents unchanged in the late 19th century the behavior of chromosomes during cell division was first observed in the early 20th century chromosomes were shown to behave like mle's units so the units were found to be genes that were actually on the chromosones in the mid2 century the structure of DNA was determined and the mechanism of how genes code for proteins was worked out the theory of evolution by natural selection is now widely accepted because of all the evidence that we now have we understand how characteristics are inherited through genes that code with proteins there was more evidence in a now more complete fossil record that shows organisms got more complex over time we can see the evolution occurring in bacterial populations that involve resistance to antibiotics in real time as they replicate so quickly fossils are the remains of organisms from millions of years ago which are found in rocks we can use them to show how much or little different organisms have changed over time there are three different ways that fossils can be Nam when parts of organisms that didn't Decay due to the lack of conditions so either lack of oxygen or certain temperatures they can be fixed in time either in Amber or ice soft parts of the animals can Decay but the hard parts are replaced by minerals this is known as mineralization often after being buried in sediment traces or imprints of organisms such as Footprints or their borrows can be preserved in we need to be able to explain why the fossil record is incomplete many early life forms were soft bodied so all of the parts decayed this is the reason that scientists cannot be certain how life started on Earth many fossils have been destroyed by geological activity imprints can be easily washed away before they have a chance to become a fossil many fossils are still undiscovered we do not know how many there are still buried and not all organisms become fossils because the conditions to make them are very rare fossils can tell us about extinct species a species is extinct when there are no individuals left here's an example from the human evolutionary tree only chimpanzees and humans are left alive in terms of species on this tree all of the other humanoid species that that are part of our evolutionary history have gone extinct want to know what can cause Extinction so new diseases or pathogens new Predators new competitors these are all very familiar from things that can change the numbers of the population and changes to the environment such as climate change these all can cause Extinction through the process of natural selection when these Chang es occur too quickly or a species is less well adapted to cope with these changes catastrophic events like a volcanic eruption or an asteroid hitting the Earth can also cause extinctions an example was the asteroid that killed the gource they are usually responsible for mass extinctions where many species on the planet go extinct all at once humans are continuing to cause extinctions now due to competing with organisms for space food and water so we're destroying their habitats or removing their ability to find food and because we are changing their habitats too quickly for them to adapt they are very miting antibiotic resistance some bacteria in a population have the ability to survive treatment with an antibiotic these will survive and reproduce passing on the genes that allow them to survive to their offspring over time we get an increase in frequency of the resistant bacteria in a population until we have a whole population of bacteria that cannot be killed by that antibiotic this is an example of natural selection and therefore evolution of bacteria an example we need to know is MSA we need to be able to suggest ways to reduce antibiotic resistance we can reduce prescriptions of antibiotics for viral infections so prevent doctors from giving out antibiotics unnecessarily making sure that patients take the full course of antibiotics every time so they take all of the antibiotics they're given even if they start to feel better and reduce the use of antibiotics in farm animals the development of new antibiotics is expensive and slow and cannot keep up with the rate of M strings this is a topic that came up in paper one and it can also come up on paper two so it's good to know and have a recap of this here because we need to know it for both the papers classification groups organisms depending on their structure or characteristics this system was developed by Carl lus here we have an example of the classification of a lion we need to know the groups in order so Kingdom FM class order family genus and species and as we go down these groups we get more and more specific to the characteristics that are more similar to the life so you need to be able to remember these in order so there's a way to remember them that I put here King prawn Curry or fat Gracy sausages that can help you remember the first letters in the right order for all of those words but you will need to be able to know that in what you don't need to know is the other side which is the actual Latin names that the groups are for the lion for example but you'll be shown examples like this in the exam and need to fill in the gaps or be able to say what the phm is for the an giv this information for example here is the binomial species name for the lion which is pan Leo it uses two words so it uses the genus and the species name to build name this is really important because it means there is a universal name and language that can be used all over the world instead of the common name like Lion which would change from country to Country it also helps having the genus as part of the B name so that you can use it to see evolutionary relationships to see what other animals would be in the same genus and therefore be closely related to the r we also need to know the definition of a species a species is a group of similar organisms that can read to produce fertile offspring originally kingdom was the highest group in this organizational system with five different categories animals plants fungi protists and proar this was the system developed by car the development of electron microscopes and understanding of biochemistry caused a new scientist called Carl Rose to update the class ification system this is known as a three domain system so a group above kingdom was added called The Domain and there were three domains ala bacteria and arcarius and then each of these has kingdoms within them so it's just the kingdom ARA the kingdom bacteria and then the ukar has all of the other eukariotic kingdoms it is just the procaryotes that have been split into these two new groups ala and bacteria so the kingdoms in the UK carotic domain are plants animals fungi and protests these were split because it was found that these two groups Aria and bacteria within the proar were significantly different enough from each other to be two separate groups so the ARA are ancient or primitive bacteria and mostly extremophiles and then the bacteria are the true bacteria what we would know is something like EOL we could walk put in the m and then other the ukar are grouped together because all of their cells contain a nucleus evolutionary trees by comparing DNA sequences between organisms and using fossil evidence we can show how closely related different organisms are this information can then be used to build evolutionary trees which shows how organisms evolve through time so here you can see we have a single shared common ancestor but all of the species a b c d and e in this group then we have a branch point and a branches off first so they were the ones to evolve first and therefore they are the oldest species then when we have a second Branch point B and C split in one direction and d and e split in another Direction and this is because d and e share a common ancestor between them and B and C share a different common ancestor between D and E are more closely related to each other than any other letter here and B and C are more closely related to each other than any the other letter here because they share a branch point and B and C actually split or evolved more recently because you can see their Branch Point shows a more recent common ancestor in time if we're using the Y AIS of time this information can also be used to improve and update p speci ifications that previously used characteristics but not evolutionary relationships so previously organisms may have been grouped together in a classification system because they looked similar but actually on looking at their DNA they are less closely related to each other than first thought so they might need to be put into a different classification group [Music] [Music] [Music] [Music] in an ecosystem there are individual organisms populations which are a group of individuals of the same species communities which are all the populations of all the different species in an area and the habitat which is the non-living parts of the environment an ecosystem is the interactions between the living and non-living parts of an area so all of the communities in a habitat interdependence describes how species in a community depend on each other they can depend on each other for shelter pollination seed dispersal and food if one species is removed it can affect the size of other populations in the community stable ecosystems have balanced environmental conditions and the species numbers in the populations are relatively constant stable ecosystems take time to develop and so examples are often hundreds of years old like large coral reefs or ancient Woodland competition all organisms will compete with other organisms for resources in their environment so for animals they compete with each other for food space or territory and mates and plants compete with each other for light space water and mineral ions competition can either be between members of the same species we call this in specific or between members of different species this is known as inter specific competition leads to adaptations that allow organisms to outcompete others in their habitat in order to survive we're going to look at adaptations in more detail but examples of things like storing food that squirrels do to make sure others can't have it and make sure they have a store for their themselves long roots of plants in the desert so they can get more water from other plants and then things like horns or claws adaptations for fighting that allow them to fight for other mates or other things like food antibiotic factors are non-living factors that can affect the number of species in populations in an ecosystem they can also lead to species having specific adaptations to survive in extreme Habs light intensity is an abiotic factor it obviously affects photosynthesis and can cause sunburn in animals temperature affects all organisms because it affects enzymes it also has an effect on the rate of transpiration wind intensity or direction again affects transpiration could potentially affect flight and it can cause exposure issues in animals moisture levels or water availability all organisms need water in order to survive soil PH and mineral ion concentration again pH can affect enzymes of organisms living in soil and plants need mineral ions in order to survive the concentration of oxygen is an atic factor in water for aquatic animals and the concentration of carbon dioxide is obviously a factor but only for plants because it can affect the rate of photosynthesis this is mostly not an issue unless these plants are in some kind of greenhouse or container biotic factors are caused by living organisms that canect the size of populations in the ecosystem new Predators ra species may not be prepared or able to adapt to avoid pration new pathogens organisms will have no resistance to the disease if they've not been infected with it before amount of food limited Foods due to reduction in population size can increase competition and reduce survival equally when there's lots of food population sizes can increase competition competition with other species for resources could lead to one out competing the other until there are not enough individuals of that species left to breed this means that they could go extinct an example I've got here is the red squirrel and the gray squirrel there are very few red squirrels left because the gray squirrel is able to out complete them in most habitats we need to be able to explain how biotic factors can affect population size an example with disease what would happen if if a new pathogen reduced the number of birds in this community it would increase the numbers of snails and worms as they now had fewer Predators but the number of lizards and snakes could decrease as the eagle now has to eat more lizards and snakes to make up for the lack of birds as they are one of their food sources so when we look at food chains like this and talk about the impact of a biotic factor on a community we have to look both above and below in the food chain a food example we need to know about predator and prey population sizes how they're linked and how they often cycle over time in stable ecosystems there are certain rules that these Predator prayer Cycles always follow as preer numbers increase the Predator numbers will increase because there's more food so more of them are able to survive and reproduce but there will be a slight delay if there are too many predators or as the population size of the Predators increases they might eat too many prey and so then the Predator population size will decrease because they now have a lack of food when the Predator numbers are low or have decreased fewer Predators means that the prey numbers can then increase because more of them can survive to reproduce if you were sketching these graphs remember there can never be more Predators than there are pre and also the Predator graph should always be lower and shifted to the right adaptations are features that organisms have that allow them to survive in their environments if we think about a desert environment it would have high temperatures high light intensity but low water these are its abiotic factors the adaptations of plants that live there often have things like long roots to absorb more water ferata to reduce water loss they might produce toxins to avoid being eaten or to kill or destroy the roots of other plants and they may have spines not leaves to reduce the surface area for evaporation but also to act as a deterrent to stop herbivores from eating them because they contain a lot of water in a cold Arctic environment it would have low temperatures low light intensities but High viability of water adaptations of this arctic fox include camouflage so being white colored to blend into the background having thick fur to stay warm hibernating during the most extreme temperatures or living in Burrows to stay warm as well on the weight adaptations can be structural behavioral or functional so example of structural adaptations here are the long roots structural examples here are the long roots the thick fur and the spies notot leaves so physical structures that the organism has behavioral is always a behavior so this example could be living in Burrows the way they live and where they when they go into the borrows and then functional is normally some kind of chemical process physiology the animal allowing it to carry out a process such as being able to produce toxic chemicals or the ability to hibernate so slow the heart rate down and slow the chemical reactions down over the winter extremer files are organisms that are adapted to live in extreme habitats so high temperature very high temperatures like above 80 degrees High pressures high salt concentrations are examples of this deep sea Hydro thermal vents have all three of these conditions and some organisms manage to survive here they are very unique because the majority of life would not be able to survive these conditions mostly we talk about extreme files and examples being from the ARA domain and these are a specific type of we need to know the organization of an ecosystem feeding relationships in an ecosystem can be shown in food chains food chains always start with a producer these are always photosynthetic organisms as these are the source of all biomass on Earth because they can use light energy to synthesize molecules like glucose the arrows in a food chain or food web show the transfer of biomass and by biomass we mean living tissue that is made up of the molecules carbohydrates lipids consumers are the first organisms that eat another organism in the food chain they can often be herbivores which means that they only eat plants and they will be Pro species because they will be consumed by other animals the secondary consumer is the second organism to eat another organism in the food chain they are predators because they catch and consume other organisms but they can also be prey to organisms higher up the food chain tertiary consumers and then we also have quaternary consumers as well these are predators and they're often carals so they only eat animals the top predator in the food chain will be the apex predator and they will have no predators that eat them it's not possible to count all the organisms in a habitat so sampling is used to estimate population size in an area we normally use quadrats these are a metal wire frame and they'll be a set size so for example one me squared and you would count the number of organisms of each species inside the frame random sampling methods are used to estimate the number of species in a certain area this is also known as the abundance as you can see in the diagram we would set up two tape measures in a way of griding the area and then we would use a random number generator to select coordinates for the X and Y AIS in order to say where to place the quadrant this ensures that the quadrants are placed truly randomly and therefore removes bias also we should place a large number of quadrants this is to improve our the liability of our experiment systematic sampling with a Transit is used to see how a changing a biotic PR affects the number or distribution of a species so where species is found so as you can see from the diagram we've laid a transect going away from the base of a tree and we've done it twice so you would lay a transect along a changing environment so a tape measure for example along a changing environment and then place your quadrants at regular intervals that means they should be the same distance apart so here we've gone for n 5 and 10 m so every 5 m along the trans you should repeat the whole transcent in a different position so as you can see here we've got two of them the change in the environment should be the same so as we said moving away from the tree and starting from the base of the same tree but there should be no overlap of your quadrants so you're not sampling the same area for both you would calculate a mean across your quadrants for random sampling you could then multiply it by the area of the field that you are measuring to estimate the total population size for the transit you would take the mean from each of the quadrats from the same distance along the transit to show the mean number of each species at each distance the carbon CLE all materials in ecosystems are recycled to provide the ra materials for new organisms to grow the carbon cycle returns carbon from carbohydrates lipids and proteins in organisms to the atmosphere as carbon dioxide so that plants can use it for photosynthesis to synthesize new molecules like glucose decomposers break down dead organisms and return nutrients to the soil for plants to take up through their Roots protos inthis is the only process to remove carbon dioxide from decomposes bacteria and release carbon dioxide as well when they respire during Decay or de composition fossil fuels and the production of fossil fuels like coal and oil takes millions of years to form and this is tracked carbon from dead organisms that hasn't decayed wood burning and burning of fossil fuels for transport and factories in order to produce energy these are all human activities and these are what put carbon dioxide into the atmosphere but these are processes that humans have cause that cause the carbon cycle to become unbalanced the water cycle is important to Prov fresh water on land for plants and animals before it returns to the Sea the first stage is evaporation where water evaporates from large bodies like the ocean due to heat and from the Sun then it condenses so it cools down to form clouds water also evaporates from leaves through transpiration precipitation Falls from clouds either as rain sleep snow and then the water percolates through rocks into the ground and runs off of rivers and ponds and other things like Farmland back into the ocean in the water cycle water is continuously evaporated and precipitated decomposers of bacteria and fungus break down dead living material or waste from animals to release small molecules that can then be absorbed they use enzymes to break large molecules into soluble smaller ones so all the enzymes we've learned about to break down starch proteins and lipids into their SCH molecules the same as digestion Decay is the process of decomposition there are factors that can affect the rate of Decay so how fast it happens temperature just like with any enzyme controlled reaction increasing it increases the rate of Decay up to a certain point moisture content decomposers need water to survive and absorb dissolve nutrients so more water increases the rate of decay oxygen concentration some decomposers can anerobic respire but most need oxygen for aerobic respiration to provide the energy needed for Decay more oxygen therefore equals faster Decay gardeners and farmers use Decay to choose compost from wasal they can also collect animal waste compost and animal waste can be used as natural fertilizer so to increase the amount of nutrients in the soil around plants that are growing they add nutrients and there's decomposes in the soil which will continue to break down compost and waste from animals and therefore make those nutrients available to the plants to improve growth both digested or waste plant material and animal waste can be used to generate biog gas large anerobic fermenters are used with specialist microorganisms that will break down the waist material and produce methane as a gas this methane can then be used as fuel in order to provide energy for HS we can model this reaction in the decay of milk in the lab but using lipase enzymes which will digest lipids in the milk to produce fatty acids and glycerol acids still lower the ph the independent variable most likely would be temperature and you can use a water B to change this between your different reactions if you're calculating rate one of your dependent variables must be time so we have to be measuring some how long it takes for something to happen so this could be a color change of an indicator which would show decreasing pH alternatively you can measure the change in PH with a pH Pro meter control variables in this example would need to be the volume and concentration of milk and lipase solutions to calculate the results you calculate the rate is either the change in PH over time or the time it took for the color to change the indicator divided by one as we know with enzyme reactions the rate of reaction should increase at higher temperatures until the point when the lipase enzyme becomes denatured or all of the lipids have been digested we need to know some alternate ways of actually measuring the rate of Decay you can measure the loss of mass over time because as biomass is digested mass is lost you can measure the temperature increase of decay of something like grass cuttings over time because as decay occurs temperature increases because heat energy is released you can measure the rate of other enzyme reactions so for example here we have a fungus which is growing on some AAR gel that contains starch and iodine so the iodine is turned black where there is starch present and you'll see there's a clear Zone around the fungus where there is no starch and therefore no iodine because the fungus is secreting enzymes such as amales to digest the starch in terms of measurement here you could measure the clear Zone around the fungus and divide that by time for different conditions environment Al changes can affect the distribution of a species which means where they are found we can obviously look at these differences in distribution using transits we need to be able to explain how different changes to these factors can affect the distribution of organisms so for example more water closer to rivers and ponds could mean that some different plant species may be found closer to there because they are adapted to bog or swamp conditions compared to others so you could look at d on this and then use this to explain how some plants were able to grow closer to the river than others temperature it will be colder up things like mountains where the air is thinner it will be warmer in different countries as or at different times of the year so in the northern and southern hemisphere we have summer at different times so where species can be found around the world can change based on temperature gases in water so for example or if there's pollution in water that can reduce the oxygen this is caused by utation and there'll be some species that can live in anoxic or low oxygen water air pollution as well there'll be some species of lyen for example that can survive pollution or some that need very clean air so where they are found could be indicators of levels of pollution we need to appreciate that these changes can be seasonal they could be geographical so where somewhere or where organisms are in the world or they could be caused by human activities such as pollution biodiversity is the variety of different species in the ecosystem ecosystems that have high biodiversity are more stable because they have reduced interdependence between organism so two examples here of high biodiversity ecosystems of rainforests and coal reefs compared to things like the Arctic tundra or the desert the interdependence has increased when there's High biodiversity because there's more food sources shelter and pollinat and so if one of these species that provides one of these Services were to go extinct or the population to decrease there would be little effect on the rest of the species in the community because there's lots of other options for them humans need High biodiversity in ecosystems in order for us to survive into the future they provide us with medicines ecotourism our food crops pollinators which we need to pollinate our food crops and resources and building materials however human activities are reducing biodiversity all over the globe and we need to try and prevent further losses of organisms in order to try and prevent their Extinction and also to help maintain all of those essential services that they provide us there has been a massive population increase in humans because we have better medical facilities and better access to food so people are living longer this means because there are more people we need more space to live and also to grow food and we also have increased living standards so we want more space and more food this creates pollution from mining building energy production farming and that all damages natural habitats on land and in water and because more people and we have more stuff we are producing more waste all of this pollution reduces biodiversity because it kills plants and animals land pollution which comes from filling up land filled with waste but also toxic chemicals in the soil which can come from things like pesticides and herbicides being sprayed onto the land water pollution comes from sewage fertilizers from Farmland and both of these create a low oxygen environment if they run into water which is done through UT tropication and it causes the death of animals like fish in the water or it could be toxic chemicals from mining or from mutti Power stations air pollution is caused by smoke and gases that have come from burning fossil fuels so the gases include carbon dioxide but also sulfur dioxide the smoke and actually bre breathing in the particulates can harm lungs of humans and other organisms living around towns and cities and the gases including the sulfur dioxide cause acid rain which damage trees plants and cause acidification of lakes and pots the greenhouse gases including carbon dioxide produce also contribute to global warming land use so again due to the massive population increase there are more people that need more space and food this means that more land is cleared for building and farming and more land is dug up for fuel for example coal oil gas and Pete or Min for minerals metals or diamonds this reduces biodiversity because we're clearing and removing animal habitats we are literally digging up and extracting the land to Quarry for building materials we remove habitats and food sources for animals but also we are killing plants when they are physically removed from an area heat is formed over millions of years in layers kind of like a special soil or compost and if left alone it creates bog or Wetland habitats that home to Unique species if Pete is extracted first they have to drain the entire area of water so it is no longer a whet contact then the PE is literally dug and extracted and cut out in these blocks and it can be used for fuel or for compost for growing plants because it's really good at growing plants by maintaining all the nutrients in the water they need the extraction releases carbon dioxide because as the Pete is extracted it begins to Decay because it didn't fully Decay which is how it's made with properties but as soon as it's exposed to the air that decay process will start also burning it as a fuel will release carbon dioxide as well so these two both contribute to reducing Pak usage as a compost has helped to reduce demand so now in most garden centers you'll see the majority of compost available to buy is Peak free also we have managed to protect most of our PE or habitats by making them sites of special sign of interest and we no longer use Pete as a these are all solutions to try and reduce impact however pee is still being extracted in other countries and imported into the UK for goose D forestation occurs to clear land for building and fing chopping down trees reduces biodiversity because habitat and food sources for animals are removed and the trees and plants are killed when they are cut down another disadvantage of deforestation is that it reduces the carbon di oxide that's removed from the atmosphere through p synthis as there are fewer trees this contributes to global the burning of wood or leaving wood to Decay that's been chopped down also releases carbon dioxide and removal of trees increases soil erosion and flooding when we say that land is cleared for building or farming where in terms of farming we mean to grow crops for biofuels or to create flat land to farm cattle or to grow rice the farming of cattle and rice both produce methane which is a greenhouse gas that also contributes to global global warming is caused by greenhouse gases carbon dioxide methane and water vapor increasing the atmosphere and trapping more heat energy from the Sun we have to be able to describe how this increase in temperature and climate changes caused by global warming can reduce biodiversity increasing ocean temperatures causes carbon dioxide to dissolve in the oceans which causes Coral bleaching or death of the cors this is obviously a really biodiverse habitat so this reduces biodiversity in corals increasing temperatures causes sea ice to melt and this produces ice habitats used by organisms such as as polar bears which contributes to their decline it also then causes sea levels to rise which reduces Coastal habitats because they flood global warming causes lots of weather changes it can increase floody in some areas it can increase drought in some areas it can increase extreme weather events like hurricanes tornadoes and Cyclones this can all cause the change of distribution of organisms so they move and they might not be able to live where they were living previously so they often have to move away and that reduces Biers in that area the changes in climate also affect migration patterns so there are organisms which migrate long distances from one side of the world or from one hemisphere to another and changing in the climate might mean that where they were going to or from is no longer suitable for them to live and so where they are flying to and where they migrate to is going to have to change scientists and conservationists have put programs into place to try and reduce human impacts on biodiversity and help to maintain it breeding programs for endangered species to try and increase their numbers this often happens in captivity in places like zoos protection and regeneration of rare habitats to try and make sure they are no longer damaged anymore and potentially help them to recover reintroduction of Hedges and Wildlife corridors around Farmland on farms normally only one crop or one species of plant is grown in large areas so allowing these extra plants and trees and everything around the edges of the field can give homes and habitat food sources to lots of other animals recycling reusing and reducing waste to try and avoid landfill and reduce how much actual waste goes to landfill reducing deforestation and the carbon dioxide emissions by governments this is normally done through legal arrangements and getting them to sign agreements to try and reduce their impact from the environment traic levels are simply represented by numbers and you start with the producer and you go up in the number as you go up F so producers are traic level one primary consumers are trophic level two secondary consumers will be trophic level three and then the tertiary consumer will be trophic level four and it can increase if you have more than four levels of the f chain you need to remember that outside of these trophic levels there are decomposers they're essential parts of the food chain they break down all the biomass from dead organisms from all of the trophic levels into small soluble molecules by secreting enzymes they then absorb the small molecules by diffusion and that's how they get their nutrition so they aren really part of the food chain in terms of tropic levels because they do consume the dead organisms but they consume all of them across the food chain to ENC Comfort them outside of the trophic levels on their own remember when we were describing the types of organisms in each trophic level we're going to use some key words things like prey which is organisms that are eaten by Predators or by other animals predators catch and eat animals for their food herbivores only eat plants and carnivores only eat animals and then obviously we have producers and consumers which we've already talked about and don't forget that we will have an apex predator this will be the Predator at the top of the food chain that doesn't have any predators of its own and one thing I will say always remember that plants so the producers are not prey they can't run away and hide they aren't being caught by animals they're being eaten by heral so plants can never be preyed if you ask you to pick a prey species from a food chain it can never be a problem biomass is all of the living material of an organism pyramids of biomass can be used to show how much biomass there is in organisms at each trophic level of the food chain so you can see I have a pyramid of boxes here and then as we go up each box box represents the biomass or relative biomass of each level food chain so we start with level one with our producer then level two our primary consumers then level three our secondary consumers and then level four our tertiary consumers there's some rules for drawing these pyramids of biomass the bars must be touching so there should be no gaps between your bars at all the bar should be centered around the middle so it should form a a sloping pyramid not kind of all over to one side The Producers will always be at the bottom of your pyramid of biomass and the width of the bars should represent roughly or the relative biomass of the organisms in each Tropic you could be asked to draw these from data in the exam so make sure you follow these rules and use a ruler and make sure you get all of those marks pyrames of biomass show the relative biomass or dry tissue mass of organisms at each trophic level the reason the boxes decrease in size as we go up the food chain is because biomass is lost at each trophic level and only about 10% of the biomass is passed on each time to the next trophic level initially producers only convert about 1% of the Sun's light energy through photosynthesis into glucose which can be used to build biomass and then energy from biomass is lost at each level due to glucose being used for respiration not all ingested material being absorbed in the first place this could be parts that are not eaten of the animal or parts that just pass through the digestive system undigested such as bones some absorbed material is lost as waste through excretion in Ura or carbon dioxide this loss of biomass at each level of the food chain limits the size of food chains to about four or five trophic levels because there's not enough biomass we be able to pass on from like the fifth trophic level to another one to actually support another organism survival we need to be able to calculate the efficiency of the energy transfer or biomass transfer and so we're going to take the biomass of the higher trophic level divided by the biomass of the lower trophic level and then times 100 so you can be asked to do this in the exam from data you're given food security is having enough food to feed a population one of the main factors affecting food security is the increasing population size which is resulted in more food being needed globally to cope with the increasing birth rates other factors include environmental changes leading to droughts or flooding which damage crops and result in famine the increasing cost of agricultural input such as fertilizer or energy needed to heat greenh houses and things like that means that not everywhere can afford to produce high quality crops new pests and pathogens damaging crops or livestock conflicts and wars in some countries reduces access to food or water changing diets in developing countries means that in demand foods are often transported around the world away from certain countries we need more sustainable methods in order to be able to feed all the people on the growing planet in order to increase yield and improve the efficiency of energy transfers between organisms intensive farming methods have been used when growing crop plants large fields of one species are planted with no hedr around the edge this is known as monoculture and it means that there is one large crop plant and no other species and the removal of hedge R helps to reduce competition from other plant species pesticides are used to reduce crop damage by insects this helps to increase yield uses of herbicides to remove weeds this reduces competition for of the crop plants which also increases yield and the use of fertilizers to increase growth of the plants you'll remember that pesticides herbicides and fertilizers can all contribute to pollution and reduction in biodiversity by killing organisms so this is why this method of farming is unsustainable and fact the environment farming animals or livestock high protein diets are used in order to try and increase growth antibiotics are put in food or regularly used as a treatment to reduce pathogen infection this is to try and increase yield because then energy is not being spent on fighting an infection movement is often restricted by keeping them indoors or small pens to try and reduce energy loss so less respiration will be used for movement also keeping animals indoors where it's warm or they can control the temperature helps to red reduce energy loss because otherwise respiration would be used to try and maintain their body temperature both of these methods help to increase the energy from their food that is then used for growth instead of being wasted this helps to increase the yield there are ethical and sustainability issues with these types of farming specifically with farming livestock people have concerns over animal welfare and also the fear about antibiotics entering the food chain as well as farming we have to think about other ways that we Source food like fishing over fishing is caused by taking too many fish out of the ocean populations so that there is not enough left to breed and replace them this is unsustainable and it causes the size of fish stocks in areas to decrease until they eventually become extinct there are some methods used to try and conserve sustainable population levels of fish fishing quers this is where only a certain number of fish are allowed to be caught at a certain time in certain areas to try and reduce the number being removed from the population mesh size of Nets if we increase the size of the holes in the Nets it allows smaller and therefore younger fish to escape so that they can have a chance to breed before they are caught and then they'll be caught again when they are older and larger because they cannot fit with CLS this allows a breeding population to be maintained and then replace the fish that c role of biotechnology alternative methods to intensive farming need to be found one solution is an agricultural solution for organic farming which would reduce the use of pesticides herbicides and chemical fertilizers which reduces the impact on biodiversity and the amount of pollution there are some suggestions here of what this would look like the only issue with this is often it can lead to either reduced yield or things like different sized fruits and vegetables maybe ones that don't look as clean or pristine as ones that you currently get in the supermarkets so some people have an issue animal farming can also be more organic it can be less intensive not using chemicals in food or antibiotics it often involves animals having a longer lifespan and living more freely roaming outside as they naturally would and only being killed in order to be used for food towards the end of their life there are also two biotechnological solutions genetic engineering and culturing microing genetically modified organisms can be produced to help humans in the future examples we've already looked at are genetically modified bacteria that produce insulin to help treat type 1 diabetes and genetically modified crops which could be more resistant to pests which could help reduce the use of pesticides or resistant to environmental condition changes like drought or flooding or they could be more nutritious so they could contain more nutrients than they would otherwise for example golden rice which contains more vitamin A microprotein is produced by the fungus fusarium it can be grown to produce high protein lowfat meat Alternatives which are suitable for vegetarians we have to know how you would grab it in this batch fer so we would need to give it glucose syrup as a substrate that it can use for respiration we would also need to provide oxygen for aerobic respiration there is a stirer to make sure that all ingredients and nutrients are mixed evenly so that all the fungus individuals can have access to them and that increases the rate of growth there is a thermal jacket in order to maintain a warm temperature and then the biomass the actual fungus protein itself is extracted and purified ready for eating do need to be careful that we have aseptic so sterile conditions around this to avoid contamination because these conditions would be great for other microorganisms that we don't want to eat to grow as well one of the main benefits of culturing micro protein instead of farming animal protein is that it takes up less space and that means there can be more space used for growing crops or bio ouch this is why in some videos I explain scratches [Music]