Transcript for:
ایڈیکسل جی سی ایس ای بایولوجی جائزہ

let's see how quickly we can cover everything you need to know for edexel international GCSE biology if you sit in exams in Great Britain you need to go to the other Ed Exel videos Link in description if you need to go there instead this is good if you're doing triple separate biology or double award that's all five topics the nature and variety of living organisms structures and functions in living organisms reproduction of inheritance ecology in the environment and use of biological resources we're going to be really moving here so pause the video if you need a bit more time to get your head around something you see let's go all life consists of cells we can see cells with a normal light microscope and maybe the nucleus but the subcellular structures won't really be visible using an electron microscope however allows us to see far finer details so we can see an image of the organel as such these microscopes have a better resolving power and a higher resolution we say we can calculate the actual size of a cell by knowing the magnification of the microscope magnification is equal to image size divided by object size therefore rearranging this we can measure the size of the image then divide by the magnification and that gives us the actual cell size we put them into two main groups eukaryotic cells have a nucleus in which their DNA is found that's your plant and animal cells for example procaryotic cells don't have a nucleus their DNA is found in a ring called a plasmid both eukaryotic and procaryotic cells contain similar organel or subcellular structures the cell membrane keeps everything inside the cell but they're also semi-permeable which means they allow certain substances to pass through plant cells and most bacteria have an extra cell wall made of cellulose providing a rigid structure for them cytoplasm is the liquid that makes up the cell in which most chemical reactions take place mitochondria is where respiration takes place releasing energy for the cell to function ribosomes are where proteins are assembled or synthesized plant cells also contain chloroplasts which contain chlorophyll where photosynthesis takes place plant cells also contain a permanent vacuo in which sap is stored cells specialize depending on the function they need to fulfill for example nerve muscle root hair xylm flm cells stem cells are those that haven't yet specialized they're found in human and animal embryos and the merry stem of plants that's the top of the choot stem cells are made in your bone marrow throughout your life as well but these ones can only specialize into blood cells we can use them cells to combat conditions like diabetes and paralysis in fact right out of the movie the island people are now getting clones of themselves made then harvesting the stem cells as these won't be rejected by the patient personally I think this is a dystopian man-made horror Beyond Comprehension you have to weigh up the ethical Arguments for yourself cloning plants can be used to prevent species from becoming extinct or produce crops with specific characteristics diffusion is the movement of molecules or particles from an area of high concentration to an area of low concentration we say they move down the concentration gradient like a ball just rolling down a hill it'll do it by itself this doesn't require any energy input so we say say it's passive this will happen across a semi-permeable membrane if the holes are large enough for the molecules to move through for example water can pass through but glucose will not at least not buy diffusion anyway osmosis is the name specifically given to the diffusion of water across such a membrane for example if there is a higher concentration of glucose outside a cell the glucose cannot diffuse in to balance the concentration so instead the water moves out of the cell resulting in a decrease in its mass the rate of diffusion in osmosis can be increased by increasing the difference in concentrations increasing the temperature or increasing the surface area this is why the Villi in your small intestine or lumpy as well as alveoli in your lungs and root hair cells for example too the Practical on osmosis goes as follows cut equal size cylinders from a potato or other vegetable weigh them and place in test tubes with varying concentration of sugar solution after a day or so we remove them dab the excess water off their surface and reway we calculate percentage change in mass by doing final Mass takeway initial mass divided by the initial mass time 100 if it's lighter than it was before this must be a negative change in mass we plot these percentages against sugar concentration and we draw a line of best fit where this crosses the x-axis is what concentration should result in no change in mass so no osmosis so this means this must be the same as the concentration inside the potato glucose and other nutrients and minerals can move through a membrane via active transport where carryer proteins use energy to move substances through the membrane as there's energy used this can actually move them against a concentration gradient for example moving mineral ions into plant root hair cells it's when cells get organized together that things get interesting though when similar cells are connected we call this a tissue say heart tissue tissues form organs for example your heart and organs work together in an organ system like your circulatory system your digestive system breaks down food you eat into useful nutrients for your body to use acid in your stomach breaks it down bile and enzymes work together in your small intestine to break it down further bile is made in the liver and stored in the gallbladder before being used what it does is neutralize the acid from the stomach and also emulsifies fats to form droplex that increases their surface area exposed to the enzyme so they're broken down faster enzymes are biological catalysts some of which break down larger molecules into smaller ones that can then be absorbed by the Villi and your small intestine into the bloodstream to be transported to every part of your body for example amalay is the enzyme that breaks down starch into glucose it's found in your small intestine and saliva enzymes are specific that is they only break down certain molecules for example carbohydrases break down carbohydrates into simple sugars amalay is one of these proteases break down proteins into amino acids and lipases break down lipids that's fats into glycerol and fatty acids they're specific because they work on a lock and key principle the substrate for example the starch binds to the enzymes active site we then call this a complex however this can only happen if the substrate is the right shape in order to fit the active site in reality they're incredibly complex shapes no pun intended these shapes here are just to represent them much like a lock and key it only works if they're the right shape for each other the rate of enzyme activity increases with temperature due to the molecules having more energy that is until the active site changes shape and so the substrate no longer binds we say the enzyme has denatured this maximum rate occurs at the optimum temperature Optimum meaning best this is similar for pH as well except it can denat at too high or too low PH the Practical on this involves mixing amalay with starch at different temperatures or with different pH buffer Solutions once mixed we start timing then every 10 seconds we remove a couple of drops and put in a spot in tile dimple with iodine in to begin with the iodine will turn black due to the still being starch present but eventually it will stay orange showing that all of the starch has been broken down calculate the time taken to do that then plot these times against pH or temperature draw a curved line of best fit and the lowest point is where the starch would have taken the shortest time to be broken down that's the optimum temperature or pH however in true biology fashion we're technically not allowed to interpolate between points for some reason so we must only say that the optimum pH or temperature is between the two lowest points shrug you need to eat a balanced diet in order to get all of the nutrients needed to keep you healthy carbohydrates provide energy starch for for example is found in bread cereal pasta and potatoes fats and oils or lipids are also a source of energy found in butter and nuts for example proteins are needed for growth and repair found in meat eggs and nuts vitamins are needed to keep you healthy and are found in fruits and vegetables too little vitamin C and you develop scurvy which ruins your gums and hair too little vitamin D can be detrimental to your bones and muscles then you develop rickets causing your legs to bow minerals or mineral ions are similar for example calcium is needed for healthy bones otherwise you can develop osteoporosis while ion is needed for red blood cells otherwise you become anemic you develop anemia fiber also called roughage sometimes is found in bread cereal fruits and vegetables this keeps your digestive system working properly water of course is needed by every cell in your body respiratory system next all to do with breathing and gas exchange breathing isn't respiration but it does provide the necessary oxygen for respiration to happen in our cells the air moves down the trachea into the bronchite then the bronchioles and ends up in the alvioli the air sacks where it diffuses into the blood vessels around it like we said earlier alvia lumpy to have a large surface area so this happens at a fast rate the oxygen then binds to the hemoglobin in your red blood cells they then transport it to every cell in your body to be used for respiration carbon dioxide made from respiration is dissolved into the plasma of the blood where diffuses into the lungs and is exhaled some water is also Al excreted this way too as you know when you breathe on a cold mirror the heart is at the center of the circulatory or circulatory system the transport system of your body we call it a double circulatory system blood enters the heart twice every time it's pumped around the body deoxygenated blood from the body enters in the right side of your heart by the way you always look at the heart as if it's yours and it enters through the vena cava the main vein into the right atrium of the heart the valve between the right atrium and the right ventricle stops back flow just like all valves to stop deoxygenated blood from going back into the body the heart muscles contract and it goes through the pulmonary artery to the lungs to be oxygenated it then comes back to the heart through the pulmonary vein into the left atrium then it goes into the left ventricle then out to the body through the aorta the left side of the heart has thicker walls as the left ventricle has to pump blood to the whole body while the right ventricle only pumps to the lungs a group of cells near the right atrium create electrical pulses that cause the heart muscles to contract the heart to beat if these aren't working properly you can be given an artificial pacemaker to do the same job blood vessels that go away from the heart are always arteries veins towards that means that arteries carry oxygenated blood apart from the pulmonary artery and vice versa for veins arteries have thicker walls to withstand the higher pressure so they have a thinner Lumen that's the hole in the middle veins have thinner walls due to the lower blood pressure but have valves to stop back flow like we said arteries split and get smaller and smaller and until they end up as Tiny capillaries with one cell thick walls to allow the fast diffusion of molecules in and out of cells the heart is a muscle so it needs its own supply of oxygen and therefore blood to keep the muscle pumping this is delivered by the coronary artery if these are blocked by the buildup of fatty deposits a heart attack can occur this is CHD coronary heart disease Sten are little tubes that are inserted into blood vessels to keep them open so blood can flow in this case statins are drugs that reduce cholesterol which in turn reduces the fatty deposits faulty heart valves result in back flow occurring these can be replaced with artificial ones along with plasma and red blood cells Blood also carries white blood cells which combat infections more on this later and platelets which Clump together to clot wounds and stop bleeding plants also have organs leaves are where photosynthesis takes place producing food for the plant water also leaves the plant through them allowing transpiration to take place the diffusing of water into roots and up the xylm roots are where water and mineral irons enter the plant the merry stem is where new cells are made like we saw earlier xylm are the long continuous tubes which water rises up we say it's unidirectional only goes in One Direction that's transporation like we said while flim are the conveyor belts of cells that transport sugars food and sap up and down the Plant we call this translocation that's bidirectional the rate of Transportation can be increased by the following increasing the temperature decreasing the humidity and increasing the air movement all of these result result in water evaporating from the leaves at a faster rate just for triple real quick the lack of nitrate ions means the plant can't synthesize proteins effectively and that stunts growth chlorosis is the scientific term for the yellowing of leaves this can be due to magnesium deficiency as it's needed to make chlorophyll the cross-section of a leaf looks like this every layer has its own specific function at the top we have the waterproof waxy cuticle not to stop water from entering the leaf but to stop it from evaporating from the top and causing the leaf to dry out the upper epidermis epidermis just means outer layer consists of transparent cells that allow light to pass through to the palisade mesophyll layer mesophyll just means a layer in the middle these are chalk full of chloroplasts so this is where the majority of photosynthesis takes place under that is the spongy mesophyll layer that has lots of gaps around the cells to increase the surface area through which gas exchange can occur carbon dioxide diffuses into the cells while oxygen and water diffuse out we also have the vascular bundle that includes the xylm and flm the lower epidermis is the bottommost layer of the leaf and it has holes in it called stamata which is how gases enter and exit the leaf the size of a sto is controlled by the guard cells that flank the hole they change size to control the rate at which gases enter and leave for example they close the stomata at night to reduce the rate of water loss as less water is needed for photosynthesis cvd cardiovascular disease is an example of a non-communicable disease as the cause of it comes from inside your body other examples of such diseases include autoimmune conditions like allergic reactions and cancer a communicable disease must be caused by a pathogen that enters your body that will cause a viral bacterial or fungal infection again more on these in a bit back to non-communicable diseases obesity and too much sugar can cause type 2 diabetes a bad diet smoking and lack of exercise can affect the risk of heart disease alcohol can cause liver diseases smoking lung disease or cancer a carcinogen is the name given to anything that increases the risk of cancer for example ionizing radiation cancer is a result of damaged cells dividing uncontrollably leading to tumors benign cancers don't spread through the body and they're relatively easy to treat however malignant cancers are when these cancerous cells spread through your body much worse as mentioned just now communicable diseases are caused by pathogens that can be viruses bacteria fungi or protists these are single celled parasites they all reproduce in your body and cause damage but viruses can't reproduce by themselves a virus is in fact just a protein casing that surrounds genetic code that it injects into a cell which causes the cell to produce more copies of the virus the cell explodes and the virus goes on to infect more cells creepy isn't it measles is a virus that causes a rash and it can actually be pretty deadly too it's spread by droplets from sneezes or coughs HIV is an STD or STI sexually transmitted disease or infection that compromises your immune system this is also called aids for short it can also be spread by people sharing needles bacteria on the other hand release toxins that damage your body cells like salmonella in undercooked food or gonorrhea another STD that causes a yellow discharge from the genitalia yeah fungi do something similar like athletes foot while protus do all sorts of different things for example malaria is caused by a protest that burrows into red blood cells to multiply then burst out destroying the red blood cell in the process it's spread by mosquitoes so we say mosquitoes are the vector for the disease not only animals though plants are particularly susceptible to fungal infections like rose black spot purple black spots appear on the leaves and then they fall off such infections can be treated with fungicides tobacco mosaic virus affects plants by discoloring leaves due to inhibiting chlorophyll production less photosynthesis occurs and that causes stunted growth our bodies are excellent at protecting us from these p pathogens though thank goodness skin is the first barrier to them entering and if they do enter your nose and trachea they can be trapped by mucus acid and enzymes in your digestive system will destroy them too if they still manage to enter the bloodstream though white blood cells are ready to combat them one type of these are called lymphocytes they produce antitoxins to neutralize the poisons pathogens produce and also they make antibodies which stick to the antigen on a pathogen and this stops them from being able to infect more cells and it makes them Clump together fact agites are then able to ingest them and Destroy them an antigen on a pathogen will have a specific shape so that means only an antibody that fits it will neutralize it if pathogens are unknown to the immune system lymphocytes will start making all different shapes until one fits miraculously your immune system will then store a copy of this antibody next to a copy of the antigen so it's ready to stop it from causing an infection next time you're exposed to it you now have immunity a vaccine is a dead or inert version of a pathogen usually a virus that exposes your immune system to the pathogen so it can produce the antibody without it infecting you for example the flu vaccine you're injected with the virus that has been irradiated so the DNA has been damaged inside so it can't do the job incidentally the cover jab however was intended to work differently instead you're injected with the DNA technically mRNA needed to trick your cells into synthesizing part of the virus including the antigen it was the first widely used jab that used this MRN technology photosynthesis happens in chlorophyll and chlorop plus in plant cells to provide food for the plant here's the word and balanced chemical equation for it and as energy is needed in the form of light to make this reaction happen this is an endothermic reaction the glucose made from photosynthesis is used for respiration or it's turned into starch or fat as a store of energy cellulose is used to produce cell walls and amino acids are used for synthesizing proteins the rate of photosynthesis is increased with higher temperature unless unless it's so high that enzyme denaturing occurs increasing light intensity or increasing CO2 concentration any one of these can be a limiting factor by the way for example even if there's lots of CO2 and it's warm if there's not enough light the rate will be limited by this in other words it doesn't matter how much you increase the other two it won't get any faster a graph might look like this before the graph plateaus levels out the variable on the x-axis has to be the limiting factor after it isn't it must be one of the other two instead if you have two lines for example different temperatures then temperature must be a limiting factor here's the Practical on this we can measure the rate of photosynthesis by submerging pondweeds in an inverted measuring cylinder we measure the volume of oxygen made over time we can instead count the bubbles but it's less accurate the independent variable could be the light intensity and that's changed by varying the distance from the light source for example a lamp however light intensity follows an inverse Square relationship in other words if you double the distance the light intensity quarters three times further 1 nth of the intensity every cell bar red blood cells has mitochondria which is where respiration takes place to provide energy for every organism for other chemical reactions to take place for movement and warmth aerobic respiration means with oxygen here's the word and balanced chemical equation as you can see it's just the opposite of photosynthesis during exercise your breathing rate and heart rate increased to increase the rate of oxygen delivered to cells for respiration anerobic respiration occurs when there's lack of oxygen glucose is instead converted straight into lactic acid which releases less energy this is what you feel when your muscles ache during intense exercise this poison can't stay in your body so there is an oxygen debt built up is turned back into glucose hence while you're breathing rate and heart rate take some time to return to normal after exercise plant and yeast cells respire anerobic but slightly different instead glucose is turned into ethanol and carbon dioxide that's why yeast is added when baking the CO2 bubbles made cause the bread or the K to rise this can also be called fermentation it's also used to make alcoholic drinks as ethanol is produced grouping all these together Metabolism is defined as the sum of all reactions in a cell or organism these can include respiration conversion of glucose into starch glycogen and cellulose glucose can also be built into cellulose which is used to make cell walls glucose and nitrates are used to make amino acids for protein synthesis fatty acids and glycerol are built up into lipid and also the breakdown of excess proteins this is turned into Ura more about that in paper two homeostasis is the term given to an organism's ability to regulate internal conditions even when external conditions change this is important so that crucial chemical reactions involving enzymes can happen at an Optimum rate amongst other things our bodies work hard to regulate blood glucose concentration temperature and water levels for example one way that our body achieves this is with our nervous system it can consists of the CNS that's central nervous system that's the brain and spinal cord and the pns peripheral nervous system the nerves that go through the rest of the body a receptor for example skin detects a change due to a stimulus like a hot hob an electrical signal travels to the spine through sensory and relay neurons nerve cells the signal travels across the gap between these neurons called the sinapse by a neurotransmitter chemical once at the spine the signal can go to the brain where you can make the conscious decision to act the signal then goes back to an affector like the muscle in your arm via relay and motor neurons so that you move your arm a reflex is when the signal bypasses the brain and goes straight through the spine to the affector this is a reflex arc this of course is much faster than a conscious decision glands can also be effective which produce specific chemicals your body needs depending on the situation for example your salivary glands in your mouth making saliva when you eat food you can investigate into reaction Times by holding the bottom of a ruler between a person's finger and thumb and drop it without warning then you measure the distance it falls before they catch it do this multiple times and take a mean average not too many times though as their nervous systems will start to get a bit better at reacting to this you can introduce an independent variable like a stimulant for example coffee or a sugary drink or a depressant which will have the opposite effect although I can't think of any ones that are legal for you at the minute to see how they decrease or increase Reaction Time respectively you could calculate the reaction time from the distance using suat s = half 8^2 but you'll never be expected to do that in this paper but it's something you could mention if you were asked a six marker on this your eyes are the most mind-bogglingly designed cameras ever conceived of accommodation is the ey's ability to change the shape of the lens in order to focus light that comes from objects that are different distances away on the retina to focus light that comes from objects that are far away the ciliary muscles relax and the suspensory ligaments tighten they're both connected to the lens this results in the lens becoming thin and that means that light is only refracted a little bit and that focuses the light on the retina to focus on near objects the opposite is true the silary muscles contract the suspensory ligaments slacken and the lens becomes fatter or thicker and so that means that it becomes more powerful actually so light is refracted more which means that the light coming from the object still converges meets focuses on the retina so you can see a clear image the pupil the hole in the iris can change size depending on the light intensity hitting the eye the cornea is the transparent outer layer where light enters the eye it has a slight lensing effect itself while the White surface that covers the rest is called the Scara the light is focused then on the retina at the back of the eye which consists of Rod and Cone stells which respond to light rods can only detect light intensity so no color while there are three different types of cones which detect green blue or red wavelengths of light a mix of which will produce the colors we then perceive when the signal reaches our brain via the optic nerve myopia is the medical term for shortsightedness you can't focus on Far objects hyperopia is long-sightedness glasses or contact lenses are usually used to mitigate this by slightly converging or diverging the light before it enters the eye laser eye surgery aims to change the shape of the cornea to achieve the same effect Thermo regulation is your body controlling its internal temperature by the brain sensing blood temperature then sending nervous and hormonal signals to various effectors around your body in order that your body loses heat to its surroundings more slowly or quickly for example if you're too hot sweat glands in your skin cause water to cover the surface this evaporates taking heat away from your body quickly blood vessels also dilate widen we call this Vaso dilation to increase blood flow to the skin to increase the rate of heat loss too cold we have Vaso constriction instead hence why you go pale you also shiver which causes your muscles to produce more heat okay back to double science goodness which is for everyone the endocrine system is a system of glands that produce or secrete hormones that travel to effectors Via the blood this is of course slower than any signal carried by the nervous system the pituitary gland in your brain can be considered the main or Master gland as it produces hormones in response to stimuli that travel to other glands in your body in order that they start then producing certain chemicals examples are the pancreas which produces insulin we'll talk more about that in a bit the thyroid controls all sorts of things like growth heart muscle and digestive fun function and more the adrenal glands produce adrenaline and the ovaries in testin release eggs or produce sperm depending on which you have speaking of the pancreas then it's involved in making sure that your blood glucose levels aren't too high or too low too high and the pancreas secretes insulin which causes glucose to move from the blood into your cells to be used for respiration any excess glucose can be converted into glycogen to store energy and that's done by the liver too low on the other hand and the pancreas produces another hormone called glucagon which causes the liver and muscles to turn glycogen back into glucose ready to be used type 1 diabetes is what you have when your pancreas can't produce enough insulin and you have to take insulin injections to do the job instead type two is when your cells no longer absorb the glucose as they should so you have to be careful with your diet and if you're overweight or obese you have a much higher risk of developing this water and nitrogen balance are triple only so skip to the next topic reproduction if you're just double your body loses water when you exhale sweat or urinate if your body has too much water let's say for example you drink too much your kidneys remove it from your blood at a faster rate where it's mixed with Ura to become urine Ura is made from ammonia which is produced from excess proteins broken down into amino acids by the liver if that wasn't the case too much water builds up in your body and too much water would go into your cells by osmosis and then they'd become turgid and burst too little water however and they become flaccid and stop working kidneys do a good job of keeping the water balance just right kidneys also filter your blood to absorb useful substances like glucose and some ions bit more detail about how the kidneys work then antidiuretic hormone or ADH is produced in the pituitary gland which travels to the kidneys and it causes the tubules in the kidney to reabsorb more water into the bloodstream so less then go to the bladder the water level is too high less ADH is produced so the kidneys cause more water to be lost in urine in both cases the water level returns to normal we call this negative feedback the term negative itive feedback might sound like it's bad but all it means is that the body responds in such a way as to return things to normal if your kidneys aren't working properly dialysis is required essentially your blood is sent through a machine that does the same job as your kidneys if this doesn't happen the buildup of Ura will poison you menstruation occurs in females after puberty eggs start to mature first FSH that's follicle stimulating hormone made by the pituitary gland causes an egg to mature in the ovary this also causes the ovaries to produce estrogen which causes the uterus lining to thicken it also inhibits or stops the production of FSH so that no more eggs mature in that cycle very clever it also causes the pituitary gland to produce LH lutenizing hormone which causes the egg to be released and it starts to travel towards the uterus via the UCT over several days finally progesterone is also produced by the ovaries which maintains the uterus lining if an egg is successfully fertilized it will embed itself in the uterus lining where it will divine to form a zygote and then an embryo the umbilical core develops between it and the uterus lining which has a good blood supply to provide oxygen nutrients and everything else the baby needs to grow even in the wound the higher levels of testosterone in a male or estrogen in a female determines the baby's physiology which then of course continues throughout their life I've already mentioned it adrenaline is the hormone that increases heart and breathing rate in stressful situations to prepare the body for fight or flight plants also have their own hormones which we can utilize when growing plants gibberellins cause seed germination to occur which we can add to seeds to give them a wakeup call it also promotes flowering and increases the size of fruits ethine induces ripening of fruits orins control chot and root growth it's destroyed by sunlight so it gathers on the Shaded side of a chute causing more growth and elongation of cells on the Shaded side so the Chute bends toward the Sun or light source this is what we call phototropism in Ro however orins inhibit growth the hormone gathers on the bottom of a root and so that means the top side grows more quickly causing the root to grow downwards this is called geotropism we can also use orins as weed killers rooting powders and for promoting growth in tissue cultures we can do a mini investigation we can put some seeds on damp cotton wool in a Petri dish for example stand the petri dish on its side leave for a few days then turn 90° and you should see that the roots have bent in that time proving that that geotropism is true for roots in order to reproduce sexually gametes sex cells must be made this happens by myosis for example in the testes to make sperm the chromosomes in a diploid cell that is 23 pairs for us are copied similar chromosomes then pair up and the genes are swapped between them the cell then divides to make two diploid cells which then divide again along with the chromosomes themselves to make four haid cells ready to fuse with another gamt which in this case would be an egg this is one way that variation occurs in Offspring the resulting diploid cell then starts to divide via mitosis which is covered in paper one plants do this with pollen and egg cells but they can also reproduce asexually but as it doesn't evolve gametes the daughter cells will be genetically identical so a clone of the parent is made by mitosis an advantage of sexual reproduction is that variation occurs which can result in organisms becoming better suited to their environment more than this in a bit so more likely to survive an advantage for asex is that only one parent is needed so for example a plant on its Lonesome can still reproduce in order for the species to survive another thing that can do both is the parasite that causes malaria as can some fungi genome is the term given to all the genetic material in an organism this code is stored in DNA of course which is a two stranded polymer in a double helix shape a gene is a section of DNA that codes for a specific protein the Human Genome Project completed its initial goal in 2003 when scientists mapped out what every Gene is responsible for coding this is powerful because it can help us identify what genes cause diseases or inherited disorders genotype is the term given to what code is stored in your DNA specifically while phenotype is how that code is expressed in your characteristics what proteins are made it affects your physiology you need to know that the monomers between the two strands are called nucleotides and they're made from a sugar and phosphate group of which there are four types A T C and G you don't need to know what the names are but a and t always match to each other in the sequence as do C and G every three of these bases we can call them are a code for an amino acid the sequence is copied by mRNA this copy is then taken out of the nucleus to a ribosome in the cell where amino acids are connected in the order needed which makes a protein the shape of which affects His function they need to be folded as well first har mutations can change a gene so much that it results in a protein being synthesized that doesn't do the job it's supposed to we now know that some DNA however doesn't directly code for proteins but it influences how other genes are expressed this is the realm of epigenetics and it's changing the way that we view DNA quite drastically back to double some characteristics are controlled by just one gene like color blindness these different types of the same gene are called alals usually characteristics are dependent on two or more genes though and them interacting dominant alals are those that result in a characteristic being expressed even if there is another alil present a recessive Al for example if you have the Al's Big B little B for eye color Big B be brown little B be blue you will have brown eyes it's only when there's no dominant alil in this case that the recessive alil is expressed so me having blue eyes I must have the gene little B little B Big B Big B or little B little B are called homozy as they only have one type of alil whereas Big B little B is what we call heterozygous we can use a punet square to predict the probability of a certain phenotype my parents have brown eyes but they both have heterozygous alals for eye color there are three different outcomes of these combining with a 25% chance of making me that's little be little be so I'm not so much one in a million more one in four my sister has brown eyes but her son has blue eyes so she must be Big B little B eye color Is by The Bu but some alals can result in disorders being inherited for example polya extra fingers or toes which is caused by a dominant alil or cystic fibrosis which is caused by a recessive alil even if two parents don't have cystic fibrosis they could still be carrying the recessive alil so their child could have the disorder human DNA is contain in 23 pairs of chromosomes but only one pair determines sex if you have XX chromosomes you are female XY you're male the expression of these genes affects every cell in your body every aspect of your physiology we can also make a punet square for these as you can see there's a 50/50 chance of a child being male or female variation is a result of the genes inherited from an organism's parents and also environmental factors Charles Darwin's theory of evolution states that random variation in Offspring will result in some being better suited to their environment than others and so are more likely to survive and reproduce but like we've seen we know that our DNA is able to respond to the environment in order to turn genes on and off depending on whether they're needed or not for example there were some blind translucent skin mackerel that were found in a dark cave when they were bred with normal mackerel in sunlight they regained fully working eyes and opaque skin within a few Generations John Baptist Lark's Theory asserted that adaptation of variation is Guided by DNA in response to a changing environment this was scoffed at but we now know that there is some truth to this thanks to the discoveries made in epigenetics bacterial resistance is largely considered to be evidence of Darwin and Evolution bacteria divides mutations occur and inevitably a bacterium with an increased resistance to antibiotics will be produced that's why we only want to use them when absolutely necessary it also means you have to complete the whole course of antibiotics if you don't weaker bacteria will have been killed off but more resistant ones will still be there and then they'll reproduce and make you even more ill if organisms are able to produce fertile offspring we say they're of the same species tigers and lions have been known to make lier Offspring but as they're infertile we don't consider tigers and lions to be the same species we can selectively breed living things with desired characteristics to enhance these for example breeding dogs to produce breeds like labrador's colleagues and if you're into undesirable characteristics pugs too they can also reproduce advancements in biology over the last few decades mean that we can also genetically modify organisms if we don't want to wait for selective breeding to do the job or when it can't actually achieve what we want it to for good or ill for example scientists have genetically modified bacteria to produce insulin which can be harvested and used to treat people with diabetes genetically modifying crops is one way of boosting their yields or nutritional value for example gold and rice has a gene inserted into it that produces vitamin A it was developed to combat diets in certain areas that were lacking in this other GM crops have been modified to be more resistant to diseases for example the process of genetic engineering goes as follows a gene is chemically cut from the organ organism that has the desired characteristic this is done using enzymes for example the gene from a jellyfish that causes it to glow in the dark this is then inserted into a vector like a bacteria plasmid or virus that in turn inserts the gene into another organism say a bunny rabbit but it must be done in the early stage of its development say just after the YK has been fertilized as this is the only way you can be sure that the gene will be present in every cell of the bunny as it grows by the way I didn't make up this example this has actually been done cloning is triple only making exact copies of plants is easy just take cuttings off a plant put them in the ground and that does the job you can also go the slightly harder route by cloning from a tissue culture that is cloning from a small group of cells this can be helpful for preserving some species from going extinct cloning animals is more difficult you can split embryo cells up just after fertilization then put them into surrogate mothers essentially you're forcing identical twins but you won't know exactly what you're getting until they've developed so if you have a fully grown animal that you want to clone you take the nucleus from one of its cells say in his skin then insert that into another's egg cell it's essentially now a fertilized egg shocking the egg jump starts the development process and it starts to divide it's then inserted into another female womb where it continues to develop carus classified organisms into Kingdom philm class order family genus and species a good nemonic for this is King philli came over for good soup the binomial a Latin name for an organism is just the genus and species combined the time went on it turned out that another level above kingdom was needed domain the three domains are archa that's primitive bacteria normal or true bacteria and ukaria that's everything else of course with DNA and nucleus of the cells ARA by the way are often found in extreme environments on the earth they can therefore be called extremophiles organisms generally compete for food water space and other things like CO2 and light for plants shelter and mates for Animals interdependence is the term given to the fact that organisms can rely on each other for these things and they can form a community abiotic factors in an ecosystem are the non-living aspects for example light temperature moisture soil PH CO2 and O2 levels in the air biotic factors are due to organisms and things like food that's available Predators prey around other organisms pathogens breeding behavior and more we can use quadrats to estimate the size of a population of an organism in a certain area by sampling around say 10% of the area taking a mean and then multiplying up for the whole area using a Quadra with a transect allows us to observe how population distribution changes over a distance the food chain shows the direction that biomass and therefore energy Flows In an ecosystem from one organism to another producers are any organism that uses sunlight to produce biomass that's usually plants or algae primary consumers eat the producers herbivores that eat only plants or omnivores that eat both meat and plants then Predators known as secondary consumers that could be Carnival or omnivores they prey on them and then we can have tery consumers as well apex predators are those at the top of the food chain they have no natural predator above them these levels are called trophic levels by the way the population numbers of all of these will fluctuate in an ecosystem over time by the way this food chain is possible I looked it up bears do eat foxes all life is carbon based which means that when an organisms die the carbon is recycled which ultimately can be used to make more organisms one way of course is when CO2 is produced which plants then used to grow bacteria also release CO2 when an organism undergoes decomposition water follows a cycle rain falls then runs into rivers into the sea then it's evaporated and the cycle continues for triple you need to know that farmers utilize decomposition to produce natural fertilizers that can then be used on crops it can also be used to produce methane gas to be used as fuel back to double nitrogen also moves in a cycle nitrogen gas in the atmosphere N2 is converted into nitrates by nitrogen fixing bacteria found in the soil or root nodules of some plants other bacteria and some fungi convert proteins into ammonia during decomposition of urine feces or dead organisms this ammonia is converted into nitrates by nitrifying bacteria now that we have nitrates they can enter plants through the roots and be used by them for growth n nitrates are turned back into nitrogen gas by denitrifying bacteria of course there's a bacterium for everything man-made fertilizers contain nitrates to help crops grow of course if too much is used water say from rain can cause it to run off into ponds and lakes where the water is still this causes algae on the surface to bloom causing a barrier that stops light from reaching underwater plants these then die and respiring bacteria feeding on this dead plant material use up more oxygen in the water starving fish and other creatures of it and they die this is urif foration biodiversity is one of those buzzword that's very much in Vogue at the minute basically it means how many different types of organisms you have in an ecosystem High biodiversity generally makes for a stable ecosystem as organisms don't have to depend on one species for a resource for example sadly human development usually results in lower biodiversity this development also poses problems when it comes to waste we're having to find more ways of disposing of sewage fertilizers toxic chemicals atmospheric pollution and more to reduce our impact on the environment one factor is the land that we need for building quarrying farming and disposing of waste an example of this is the destruction of Peete bogs to make compost which affects the habitat of many organisms and microorganisms burning Pete also releases CO2 now going off peace for a second for your exams you need to say that carbon dioxide and methane contribute to global warming personally I'm not so sure especially seeing that carbon dioxide only accounts for 0.04% of the atmosphere while methane is 0.18% you decide who's telling porkys incidentally water vapor is responsible for 95% of the greenhouse effect but you never hear about that do you anyway deforestation bad on a big scale flattening forests reduces biodiversity and it's often done to create Farmland the Pyramid of biomass is a food chain that shows us how much mass enters the next trophic level relatively you need to be be able to draw one on graph paper using numbers supplied in the question and also calculate the percentage absorbed by the next level as per usual percentage is equal to the bit divided by the lot time 100 of course this shows that biomass is lost at each level because it's not just a rectangle as not all biomass is absorbed or consumed into the next organism some is lost due to the organisms living for some time before being eaten by a predator for example it's also lost as water Ura and CO2 food security is a big thing especially in these uncertain days food is becoming more scarce due to increasing world population changing diets food being transported around the world which requires H amounts of energy changing growing environments the cost of farming that's a big one of the minute and conflicts for example around 40% of the world's wheat comes from Ukraine or at least it used to farmers are constantly trying to find more efficient ways of farming largely by maximizing biomass input to crops and animals while also reducing biomass loss by them fishing sustain is also important if a species is fished at a greater rate than its breeding then its population can disappear in those areas one way of sustainably fishing is by having Nets with holes in that catch adult fish but are big enough to let the little ones out if young fish aren't caught then they go on to breed so there you go hope you found that helpful if you did please leave a like click on the card to go to the playlist with all three videos he after you've done your exams why you come back here and tell us how you got on we'd love to know all the best but