hello everyone today we're going to be going over the January 2024 living environment reading exam uh we're going to be looking at part A which is 30 multiple choice questions starting with number one which says that homeostasis in single cell organisms is maintained through the proper functioning of what it's proper functioning of organel homeostasis is your body's or an organism's way of maintaining uh balance right so uh in a single cell organism right uh you don't really have antibodies guard cells or estrogen because these are multicell these are things that are found in multicellular organisms right um so like big complex beings like humans dogs cats things that are made up of multiple cells organells on the other hand are found in all cells including single- cell organisms right uh and organel work together to keep a singular cell alive so number two says in a stable ecosystem each Niche is usually occupied by one specie the specie occupying a particular Niche is able to continue to remain there as a direct result of what well ecological succession is is wrong because ecolog ecological succession kind of refers to um starting a new environment so for example if you had a a big Forest that that all of a sudden went up in flames and burned down and then it turned into like a plot of dirt and then over time grass started growing on that dirt that would be ecological succession right but the fact that that grass remains in that environment is not um or or the fact that that grass has a niche is not explained by ecological stion it's actually explained by favorable adaptations right so um so the the thing is each part of an environment has a very specific place right so for example if you are um I don't know living in a rainforest and you are a bird right you usually you tend to live in the uh upper part of the rainforest right you you tend to live in the trees rather than in the ground right uh if you are for example a sloth you you instead of living on the on the actual uh leaves of the trees and the upper branches you you live on the branches if you are a um I don't know for example a snake you might live on the ground uh and the fact is that each of these have a very specific role the bird will for example go to the ground and eat seeds and then the snakes will then eat the birds that land on the ground or the snakes might crawl up the tree and eat the sloth but they're all able to do this because they have evolved to fit that very specific spefic role the birds have evolved to have a certain like wingspan to allow them to efficiently fly up and down these massive trees or the snake might have adapted to have like very good eyesight so that it could see uh the birds that are that are are swooping down and they could kill it and and eat it properly right so the the reason that they are able to continually survive in in this Niche the reason that the snake is is forever able to survive on the floor of the rainforest is because it is adapted it is is adap Ed to that environment right and it's adapted in such a way that allows it to effectively uh survive in that environment right so number three says that when exposed to ultraviolet UV light human skin cell produces the protein melanin this protein helps protect skin cells from damage caused by UV light this is an example of what well what is this question saying it says that when exposed to UV light humans skin produ proteins right so what does that mean that means that in response to an environmental factor for example sunlight sunlight emits UV radiation right this UV radiation is then absorbed by our skin is our skin and all of a sudden we start producing melanin we start producing melanin we start producing proteins but guess what has to happen when you produce a protein you have to transcribe a piece of DNA right how do we make proteins where do proteins come from proteins come from our DNA right we we have our DNA then we transcribe it into mRNA right and then we we translate that mRNA into protein right and that protein in this case is melanin but what caused this change actually is um an environmental Factor right that UV light activated something within our gene or something within our DNA that then triggered that DNA to replicate triggered that DNA to transcribe into protein and then triggered that protein to translate into uh into melanin right so it's environmental factors affect gene expression so the UV light affects how we express melanin so number four says that the human pancreas contains cells that secrete ins insin only these cells produce insulin because of what well number one uh cells eliminate the parts of genetic code that they do not use this is false right cells actually have all of your cells except for your sex cells have the same 46 chromosomes in them right nothing is deleted number two says all other cells lack the genes for insulin production this is also false because otherwise number one would be true all of your cells have the except for your sex cells so aside from sperm and egg cells everything else has the exact same 46 chromosomes to the exact same way right three says different cells use different parts of genetic information that they contain yeah this would be this would be correct right we all of our cells right they all have a nucleus and that nucleus they all have those same 46 chromosomes they have the same genetic information but the the replicative Machinery the thing that transcribes that and replicates that DNA only transcribe and replicate specific parts of DNA when it comes to produce proteins or when it comes to actually functioning right so for example uh your muscle cells right cells that are in your muscle when you like Flex uh these cells located inside your muscle are going to use different parts of those of your genetic information to to I don't know maintain myosin or maintain like the the high amount of mitochondria that they need or or this to maintain in their specific structure right and this might be different than the cells in your pancreas that have you know enzymes and proteins that produce insulin right but the at the end of the day they have the exact same identical genetic makeup it just Express different ly and number four says they are not they are the only cells associated with digestion of sugar this is false because uh think about what your stomach cell cells in your in your stomach cells in your small and large intestine those definitely digest sugar right so different the the key Point here is that all of your cells except for sex cells have the same amount of DNA it's just they use different parts of it so number five says in humans two organ systems work together to move oxygen throughout the body and deliver it to the cell which system directly delivers oxygen to body cells well um it would be the circulatory system because the respiratory system uh and this is and this is kind of a trick question it's kind of tricky because obviously you can eliminate nervous and digestive because digestive does what digestive breaks breaks down food into energy for your body to use and the nervous kind of send signals to control your body so to move and to breathe and to um I don't know decide to make a YouTube video right that's what your nervous uh system does but here respiratory and circulatory these are two very similar or or tricky answers it asks us which delivers oxygen right so so it cannot be respiratory because respiratory is what oxygenates the blood your lungs they don't they don't push that blood all over the system what they do is they allow oxygen or O2 right to um to enter your body and then it allows you allows it to put that O2 into your blood cells so for example your blood cells uh you need oxygen to live right why why do you need oxygen to live you need oxygen to live because of cellular respiration which which is what makes ATP and you need ATP to move to breathe to it's the energy source right so when that O2 is used up those blood cells now have CO2 in them right and CO2 is bad so those blood cells go back into the lungs where you now breathe in new O2 and the your lungs pretty much take out that CO2 right and put in that O2 into the new blood right so now all the only thing the respiratory system really does is it just filters your blood it filters out the carbon dioxide in your blood and it adds oxygen to your blood then then what ends up delivering that oxygenated blood outside of the lungs is your circulatory system it's the many arteries and veins that are leading into and out of your lungs right um so it's it's all the blood vessels it's your heart that actually pumps and and actually like flows new an old blood oxygenated and deoxygenated blood throughout your body so it'd be your circulatory system number six says currently Turtle populations are decreasing in September are decreasing in September 2018 a scientist stated that Turtles contribute to the health of many environments and that the decline of turtles may lead to NE negative effects on other species which statement best summarizes the scientist statement living organisms interact with and are dependent on on their environment and on each other you know before reading the other ones I'd say this is correct right um number two of very large animals turtles are very large animals and thus have a negative effect on their environment wherever they live this is false right because no one said that Turtles are large animals in his statement no one here nowhere here does it say that Turtles are bad or that they're large animals they can be small number three says if organisms have a negative effect on their environment there is probably a technological fix available though this may be true that's not what he said he said nothing about technology number four says the decline of turtles will not really matter because relatively few humans rely on them for food this is a summary right this is an opinion but it's asking us for summary nowhere here did he talk about humans needing food what he did say was that when when um when Turtle populations go down so when there are no more Turtles left no more Turtles Left um it's bad for other animals right it leads to negative effects on other species so when you don't have Turtles the environment suffers and guess what this one says this one says that living organisms interact with and are dependent on their environment and on each other so living organisms are dependent on each other because they interact with each one another if other animals if the popul of other animals decreases when the population of turtles decrease that means that they are dependent on one another because the population of one depends on another number seven says which set of substances are molecular building blocks that directly form some of the complex organic molecules present in humans right so which set of substances so there's going to be multiple substances and they're going to be building blocks they're going to be building blocks that directly form some complex organic molecules so each one of these choices right each one of these choices has to make up a organic molecule like within itself right so for example um each one of these choices you need water and water water is going to be a building block for a complex organic molecule right so it has to just be that choice um and it has to form a complex organic molecule so it has to form something that is made up of many other molecules and something that has a very interesting structure so for example uh like a DNA a DNA is a complex organic molecule because it has a bunch of like twists and turns and it's made up of sugars and phosphate groups and nitrogenous bases right it has a lot going on in it and a protein a protein can also be a complex organic molecule because it's made out of organic things same thing with DNA but it also has a bunch of twists and turns and and sheets and functions and binding sites and it's very complex because it's made up of a bunch of things so those are some examples of complex organic molecules and I could eliminate traces one and two because um oxygen isn't a building block for anything right uh you can't make a giant protein or DNA out of just oxygen alone same thing with water if you have a bunch of water you have like a lake that's it like it doesn't build anything right starch and nitrogen the same thing right nitrogen isn't directly responsible for building any like complex um molecule or anything like that carbon dioxide and proteins the same thing happens here although protein complexes do exist where it's like one Protein Plus another protein make like one super protein with a bunch of complicated things for example like hemoglobin where it's like hemoglobin is a protein made up of four other proteins carbon dioxide doesn't make any complexes right there's no protein comp there's no just molecular complex that's made out of CO2 right um CO2 is CO2 you have a bunch of CO2 guess what you have smoke um and it leaves us with Choice four by process of elimination glucose and amino acids and you could kind of figure this out because guess what uh amino acids when you have a bunch of amino acids together AA plus AA plus AA all these amino acids form to make a long chain of protein right so a long protein chain so amino acids are building blocks right all the rest of these were not building blocks for any other molecule really and glucose makes glycogen and glycogen are the is this like large complex molecule which it's like kind of this long web of just sugar sugar sugar sugar sugar sugar all bound to one another and sorts a bunch of energy in it right so amino acids and glucose are both building blocks to these long chains of uh of they they form long chains with one another to make these complex Pro uh molecules right so number eight says the diagram below represents a process that occurs in many cells the main function of this process is to what well what process is this this is DNA replication how did I know this was DNA replication well number one you're going from a double stranded this is this has two strands strand number one strand number two and you're then creating two copies of it two double stranded copies this is also double stranded strand one here strand two and this is also double stranded which is strand one strand two now the second way I knew that this was DNA replication is because here we have a thyine and here we have a thyine remember that uh DNA has thyine and RNA has uracil right so because we we we're going from something that has t to another thing that has t this we know that this is DNA replication right and um we know that DNA replication uh is needed for what and that's what this question is going to answer DNA replication of course is needed to provide exact copies of genetic code before celf division right because this is going to produce an identical two identical copies of itself right produce variations in cell before asexual reproduction that would be a mutation also that's not a that's not a process that's a random chance two synthesize antigens needed to combat immunity uh this would be false because if you want to synthesize antigens you would make proteins so in this process would be uh mRNA to protein and four make proteins needed for cellular met uh metabolism that would once again be mRNA to protein but here what we're doing is we're we're copying our DNA into two so that we can then split because the DNA that we just copied is now going to go to our our our daughter cell right so here we have one cell and if I want to make another cell if I want to split this into two cells both of them need to have the same DNA inside one another um but in order to get that I need this one cell to have double the DNA which I'm going to get by replicating my DNA so number n says which interaction is an example of a competition I between two species so mice and Chipmunks eating sunflower seeds at a bird feeder mold growing on a turtle that has fallen in a forest this is not competition because um a uh sorry mold mold growing on a tree that has fallen in the forest this tree is now dead this mold is now decomposing right so the tree is dead how are you going to compete with something that's dead doesn't make sense number three says a coyote feeding on the remains of a squirrel killed on the road this isn't competition because what you can't compete with someone something that is dead uh a car the car cannot eat it right so the car killed it and then the coyote found the dead body and ate it right so there's nothing being um there's nothing there's no competition going on because it's just eating what's or or interacting with this environment number four says a lion stalking killing and eating a zebra this is also not competition because it's just being a predator right there's if if there was another lion present then yeah maybe there would be competition but what's happening here is that he just that's the process by which he gets his food right and there's no other lines to stop him so number one a mice and Chip mice and Chipmunks eating sunflower seeds in a bird feeder is competition because they're both doing the same thing they're eating the same food within the presence of one another so yeah they are competed because there's limited amounts of sunflower seeds there everything else here was just either number one an animal just acting alone or number two an animal interacting with something that was already killed and with something that and there was no other animals present here so for competition you need two different species to be uh present in one moment doing the same activity right so number 10 says one significant one important reason that humans have a significant effect on the Art's ecosystem is that what humans remove large amounts of carbon dioxide from the air uh humans are able to increase the amount of finite resources humans can modify the environment through technology or they can reproduce faster than other animal species this is false because uh we don't it takes nine months to make one human it takes six months to make six dogs so we don't reproduce faster than other species um we don't affect the Earth's ecosystem because we remove large amounts of CO2 we actually add we add large CO2 uh large amounts of CO2 into the air um through our cars through these factories through our airplanes right so now that leaves us with Choice two versus choice three we are not able to increase the amount of finite resources for example oil is a finite resource we can't make more oil unless we um but we can't unless we all die and then two Milli like a million years passes and we we form oil ourselves right so number three we can modify the environment through technology and we could either modify it in a good way or a bad way so for example the invention of the car was was was a new technology but it modified our environment by ining our CO2 output because the cars use CO2 um at the same time we can modify our environment by developing new technology to discover new amounts of oil right or or use more oil which then leads to more greenhouse gases and US changing our environment more by like increasing the temperature or we could develop new deforestation techniques that allow us to uh chop down and cut through forests much quicker right so we affect our ecosystem because we have all this technology 12 says that within 10 years of the introduction of a new mosquito spray very few descendants of the targeted mosquito population were killed by the usual dose of the spray so what happened here and they're asking us what's the best explanation well what happened here was that we introduced a new uh mosquito spray 10 years ago right let's just say that this is the can it goes and it sprays out there and at some point it was really useful and it killed all the mosquitoes but then 10 years went by and now the same spray cannot kill mosquitoes right you spray it you spray the exact same amount and the mosquito is still alive right so why could that happen number one says ingesting the spray caused the mosquito to become resistant to it this is false because this is a change that happened over 10 years if spraying a mosquito with the spray made it more resistant to that it wouldn't have taken 10 years for everything to be resistant right number two says the spray polluted the water which in which the mosquito deposited their eggs this doesn't mean that the mosquitoes are now resistant to it this just means that this would do the opposite right this wouldn't that kill more mosquitoes if the poison got to their babies first number three says the mosquito the spray killed organisms that cause decrease decreases in oh my goodness the spray killed organisms that c diseases in the mosquitoes this is this is you can't know this for a fact right maybe it did maybe it didn't but the fact is that the mosquitoes themselves have become resistant to the spray right the more that you spray it the less it affects the mosquito it doesn't matter it doesn't mean that like after 10 years after the spray was used all of a sudden the mosquito population is greater the question is not saying that the question is saying that the mosquitoes themselves are affected way less by the spring spray when you directly spray them so it doesn't matter if their population has increased or decreased what matters is that the mosquitoes themselves are no longer affected by the spray which leaves us with number four it says existing variations in the mosquito population provided resistance to the spray one mosquito could have had a mutation right that that made the spray not effective anymore and then it had a bunch of kids that also had that resistance Gene and then they just adapted to not react to the poison at all right number 13 says once implanted into a recipient bioengineered blood vessels made from plastic like material become covered with the recipient's own cell in advantage of using these bioengineered vessels is what well it has to be that they do not trigger an immune response right so think about it you have these blood V the the number the biggest issue when when you have something entering your body you have a foreign object that doesn't belong in your body entering your body is that it triggers an immune response right an immune response and this is bad because for example if you're if you're donating kidneys right if you're an organ donor you have someone else's organ inside of you and that causes your body your body recognizes what belongs inside of you and what doesn't belong inside of you it recognizes that hey this organ isn't my own organ this is a foreign body and guess what it has disease and I need to kill it and the same thing happens if you were to like swallow um like a piece of of metal right if you swallow a piece of metal your immune system is going to attack it because that metal has bacteria and germs on it that are really bad for you and the same thing happens when when not just organs but you have like a metal implant that that's implanted in you or you have some foreign body inside of you your body is going to start attacking that because it doesn't belong there so what's happening here is that bioengineered blood vessels made from a plastic like material become covered with the recipient's own cells so because you're covering this this thing entering your body with your own cells your body now thinks that it belongs there right it's like it's it it has no antigens on it it it because your your obviously your body is used to your own yourself right your skin your body isn't going to kill attack its own skin cells because guess what it's your own skin cells it can recognize what's you and what's not you so if you cover if you cover this implant in what is you which are these skin cells guess what it's not going to it's not going to detect an issue because it's just going to detect that thing that's covered in your own cells as your own right so it doesn't trigger your immune response number 14 says unlike telephone messages that pass over telephone wires messages between parts of the body are carried by a series of nerve cells that are not in direct contact with one another communication between two nerve cells is represented in the diagram below which statement best explains how messages how the message is delivered even though these cells are not physically connected to one another so you can see you should know this that it's it's contacted by neurotransmitters this cell is going to release molecules that are then going to bind to this end of the cell and and carry the response forward right so it's the release of molecules called neurotransmitters and even if you didn't know that you can kind of figure that out here these uh these black things are actually the neurotransmitters that are then going going to enter the synaptic C bind to here and then carry the response forward right so um so let's communicate with the use of chemical Messengers between them that's the best answer Choice here uh this is what I just said number 15 says a saltwater aquarium contains a variety of saltwater fish and plants members of a species of small fish from a freshwater stream were accidentally added to the saltwater tank within an hour all the fish that were added were dead while the saltwater fish were still healthy the freshwater fish most likely died because they became severely dehydrated due to the process of diffusion there's a reason why you saltwater animals and not saltwater animals uh fresh freshwater animals are things that can survive in low solidity environments saltwater animals are animals that can evolve that can that have evolved to survive in high salinity environments why is drinking really salty water bad for you why is drinking sea water is bad for you because it has a bunch of salt in it right yeah sure it's water you need water to live but you need water that doesn't have salt right because if you drink salted water it's actually going to dehydrate you and it's going to do the opposite of hydrate you it's going to take more water out of you because that's what salt does salt draws water from people and from things so now imagine you're covered in salt your skin is going to become irritated you're not going to be happy because salt is going to dry you out what these saltwater animals have are these adaptations that allow this them to be resistant to the Salt so the salt doesn't drive um it doesn't drive moisture out of them right so all of a sudden you have these things that are susceptible to salt and you put them in a salt environment the salt's going to do damage right um number two is wrong cuz you salt would do the opposite it wouldn't cause you to take in too much water it would cause the water to leave right um had no freshwater organisms to eat in the saltwater tank starvation has nothing to do with this it happens it has to do with salt right um and I guess I'll explain it further what this means is that if you are put in a high salinity environment so for example if you're put in water that is very salty this is you and this is your and this is your environment NAC NAC na n nature wants to go from a high envir high salinity to low salinity right so in a and it wants to go from a high concentration to a low concentration inside of you there's very few NAC outside of you there's a bunch of NAC so the universe wants there to be an equal amount of NAC and H2O H2O H2O it wants there to be an equal amount of H2O and NAC inside and outside of the cell so because you have no salt to offer the only way that and and you have a bunch of H2O inside of you right so the only way that I can make balance is by making this H2O leave leave yourself so that uh the outside is more like your inside so the outside has more water just like you right so water is going to then leave your cell for that reason number 16 says that an energy pyramid containing uh green plants and other organisms from a food chain is represented below herbivores most likely be located in level two only right level one is going to be the producers level three is going to be like apex predators or predators in general so it can't be level one and three it would have to be level two only right so this is an axotal cute axotal also known as a Mexican walking fish can regenerate parts of a body such as a leg and a tail the Regeneration of these parts involves the process of what well it has to be mitotic cell division right if you want to make more copies of a cell you have to undergo mitosis mitosis is the process by which you make ident copies of yourself so if you may if you copy your cells enough so many times they're going to then form like these these these um clusters right and then those cells if they pile on one another you can actually end up growing a brand new limb so it has to be through mitotic cell division fertilization would be if you wanted to make a brand new axotal biotechnology there's no technology here they evolved to be able to do this and selective breeding humans did not breed axotal to um be able to regrow limbs they did that themselves right so number 18 says which of the which would most likely control an insect Pest and be least harmful to the environment right so eliminating the plants that the insect past feeds on this would be false because guess what what if what if animals that belong in that environment also feed off of that plant and because you took away that plant you also took away natural animals uh source of food which is really really bad right so that would be that would cause a lot of harm number two says using traps beta with sex hormones that ATT attract the insect pest um I'd say that this is a valid choice right because it's sex hormones that attract the insect pest these are very specific hormones for the insect right so two would be the correct answer here um because it's only going to attract insect pests and it's going to trap them right other natur other animals that belong in the environment aren't going to fall for these traps because they're not going to be attracted to them like the pest number three says releasing important insects that prey on the insect pest this is also bad because guess what what if these an what if these uh insects that prey on the insect pest they also don't belong in that environment right so you're int you're trying to deal with an invasive species by introducing another invasive spey what if for example their population goes out of control what if they start eating all the grass in the area and all the grass in the area in addition to the uh to the pests right then they ruin the environment further this is what happened in Australia when they had like a a cricket outbreak or like a they had a rabbit outbreak and by that I mean like there was a bunch of rabbits there and they were really killing all killing off the environment so in order to combat combat that they imple they uh British government kind of threw in a bunch of U snakes into their environment and they lost control of the snake population and sure the rabbits were all killed but then guess what they now had to deal with a brand new snake infestation number four spraying the insect with areas with insecticide would be also bad because it could be harmful to the plants and animals there number 19 says which statement concerning the function of cells is correct mitochondria transfers energy from organic compounds to form ATP molecules I'd say that this is correct right mitochondria is the PowerHouse of the cell you go from organic molecules such as glucose and you form ATP vacul are a sites of DNA synthesis that's false that's the nucleus the nucleus stores genes that will later be removed from the cell genes are not removed from the cell the cell membrane prevents the diffusion of all poisons into a cell from its environment that's also false because um because then poison wouldn't work if the cell membrane stopped poison from coming into the cell then it wouldn't be poison no one would be affected by it right the cell membrane cannot stop everything from coming in number 20 says that a photograph below shows the result of a deadly wildfire in California in 2018 what is most likely expected to occur in this ecosystem in the future will it eventually restore itself but be very different from the original um not really right because who's to say that you can't re that those same trees can't regrow in the same area right the ecosystem will eventually restore itself and be similar to the original this is true because guess what just because these tree burn these trees burn down doesn't mean that it's not a suitable area for another Forest to come back and regrow into uh the climate could be good for a forest the amount of moisture in the soil could be good or nitrates in in in the soil can be good for um the environment or for for a forest ecosystem right so just because one Forest burned down doesn't mean another Forest can grow from there uh the ecosystem will be completely reestablish after 6 months you can't know that it's going to be established after 6 months and the ecosystem will be unable to reach a state of stability again you also don't know that that's not guaranteed what you do know is that you had a forest environment you had an environment that could support a forest before the fire then the fire killed all the forest but guess what it didn't kill the environment the environment is still there it's still suitable to grow a forest you just need to replant those trees right so 21 says uh the kittens below are were born in the same litter the kittens in the same litter often have similar characteristics such as for texture markings because they what because they inherited similar genes right uh the time that you were born doesn't matter what matters is that uh they came from the same mom cat and mommy cat and Dad cat um that had for example dark and light fur for example if the mother had light fur then this cat could have inherited its light fur from the mother right um and this is just how they get the markings in general markings is going to be genetic fur texture is going to be genetic if you have a hairless cat and it has babies with another hairless cat it's Offspring its kittens are going to be hairless because it doesn't have the gene for hair right so they all inherit similar genes because they all came from um the same parents right uh milk doesn't really affect this right because the the genes were already transferred um during fertilization and the fact that they develop in the same environment doesn't necessarily matter number 22 says damage to which structure would most directly interfere with the nutritional needs of a developing embryo uh that would be the placenta the placenta is kind of this this um or organ that directly transfers uh blood and and waste into and out of the embryo right so if placenta was destroyed uh also the umbilical cord uh actually connects to the placenta so that the placenta is like the the um the main Center for which uh nutrients come in and out of that baby right so if the placenta was was destroyed then guess what there's nothing to feed into the child anymore there's nothing to take out of the child anymore right so nutrients go into the placenta and then they go from the placenta through the umbilical cord to the baby number 23 says the body's IM uh the body's inability to regulate blood pH could affect what the enzymes that function within the circulatory system there red blood cells ability to fight infection this is false because red blood cells don't fight infections three white blood cells ability to carry oxygen this is also false these two are mixed up right they should be the other way around red white blood cells fight infections red blood cells carry oxygen four it could affect DNA that controls starch digestion in circulatory system maybe but number one is a better answer right because enzymes that enzymes operate at a specific salinity they operate as a specific pH level and they operate at a specific temperature if the pH level is out of is is out of balance that means that the enzymes function poorly or more or or they can't function at all right so for example if you have a high pH a protein could denature and and enzymes are are usually made out of proteins but same thing with enzymes right uh if an enzyme looks like this when the pH is seven if you decrease the pH to two the enzyme can now look like this and guess what the very specific shape that binds to this enzyme can no longer bind to this enzyme right so think about the uh pH level as it as something that affects protein and enzyme function number 24 says test anxiety and stress can trigger many responses in the human body it can stimulate increased heart and respiratory rates and increased sweating these physical responses are responses to increased stress are example of what they're example of feedback mechanisms right it's not Gene manipulation because no genes are being manipulated here uh you don't need a gene to have a heartbeat quickly that's just a response right it's not an infection because anxiety isn't an infection in competitions well yeah you can well that's not what they mean by competitions here competition between animals guess what that's not it these are examples of feedback mechanisms if you are in a high stress environment for example there is a predator that is in front of you and it is about to eat you you need to be stressed you need to increase your heart rate so that you are ready to fight or that you you have enough blood in your system to run away uh you need to increase your respiratory system so that you have the most oxygen in your body so that you can produce the most ATP and have the most oxygenated blood so that you can have high movement High sweating you want to be able to regulate your envir your your body temperature during uh these these high bouts of movement that you're getting ready to do right so these are all feedback mechanisms to a stressful environment 25 says a self-sustaining ecosystem in a glass tank must include what well if you're self-sustaining that means that you don't need any external source of energy so it needs to the environment needs to be able to produce its own source source of energy right and I mean energy in the source in the terms of food right so uh normally you have producers and producers are the things that make the energy for the environment they take H2O and they take uh CO2 and they take water oh sorry they take light right sunlight and they produce their own food and they grow and then herbivores then herbivores then consume producers and then Predators then consume um Predators then consume those herbivores right or carnivors would consume those uh herbivores but the fact is those herbivores were able to grow because they got the energy from the producers and those producers were able to grow because they got the energy just from their environment um and then once everyone dies decomposers come in and they um they decompose the dead animals right and they release nutrients into the soil which allow producers to grow right so what I'm trying to get at is that choice number one kind of has what I was talking about right it has producers decomposers light water you need light so that the producers can undergo photosynthesis you need water so that the producers can go undergo photosynthesis and you need decomposers so that you can restore and replenish resources back into the soil where the producers came from right if you don't have decomposers what's going to happen is you're just going to have a bunch of dead plant corpses and and you're going to run out of space you need those decomposers to get rid of those dead plants so that there's more space for brand new new plants to come out of and to grow out of heterotrophs water and carbon dioxide doesn't make sense because if you're a heter tro you can't make your own food if you have a bunch of like earthworm earthworms and you put them in a in a glass tank with water they're all going to die because they're not going to have any food right and uh decomposers heterotrophs light water and carbon for the exact same reason if you put a bunch of things that do not make their own food in an environment that does not have any food guess what um even heter trops if even if you put like predator and prey event the prey needs something to eat too and that thing that they eat is going to be plants right and eventually all the Predators are going to kill off all the prey and everyone's going to start right herbivores consumers decomposers and water this is missing the key factor of producers because guess what what are the what are the consumers going to consume right obviously the Predators are going to consume the prey but what is the prey going to consume they have no water this s they don't have they have no plants or producers to consume the 26 says a scientist examine 39 tree species from warm and cold areas of the Earth and found that the trees were able to regulate their Leaf temperatures keeping them about 21° C this meant that the tree leaves were able to be cooler than the environment in warm areas but warmer than the environment in cool areas this is an example by what this is this is an example of maintaining homeostasis by responding to environmental change right so you're maintaining homeostasis because you're maintaining your temperature and you're you're reacting to an environmental change for example the day and night cycle things are colder at night and warmer during the day so you need to cool off your leaves during the day and warm them up during night right failing to respond to environmental conditions this the opposite right they're they're able to regulate themselves to 21 degrees C they're not decreasing evaporation for uh for cooling during evening hours because they're also increasing that this has nothing to do with evaporation what this what what this has to do with is the fact that you're maintaining temperature number two says controlling carbon dioxide released during daylight hours that's also false because this has this has nothing to do with temperature number 27 says a diagram below represents a food web uh two carnivores represented in this food web are what well what does that carnivore have to do carnivore has to eat other animals right so for example uh it cannot be a deer because guess what deer eat plants not other animals it can't be mice because mice eat plants not other animals it can't be grasshoppers because guess what grasshoppers eat grass not other animals so it could we're we're we're left with Wolves snakes toads and raccoons deer and mice we just eliminated grasses and grass I also can't be grasses because grasses don't eat anything other than sunlight and water right it can be it can't be deers and wolves it can be toads and snakes because snakes s eat snakes eat toads and mice and toads eat grasshoppers right so number 28 says a sea slug found along the eastern coast of North America is known to have an interesting relationship with algae the sea slug incorporates part of the algae into its tissue this allows the sea slug to directly use energy from the Sun uh which structure from the algae would the sea slug need to accomplish this it would need chloroplasts to accomplish this right the algae is green because of the chloroplast the chloroplast is where photosynthesis occurs because you can it it's where um you have water in combination with with uh CO2 and sunlight to produce energy right so you need chloroplast for that number 29 mitochondria on the head is how you produce ATP chloroplast is how you would produce sugar from uh from the sunlight number 29 says which three processes usually result in the greatest variety of possible genetic combinations right so you would need you would definitely need need mutations for this um because the greatest variety is usually the way that genes vary in an environment is through random mutation right a lot of our adaptations came from random mutation and this seems to be the only choice with mutation so yeah um meiosis because meiosis is where crossing over happens it's a mixup between two parents so if you want kids that vary you don't want them to inherit 100% of your DNA you want those kids to inherit 50 from you and 50 from your partner right because then you have a mix you have something unique and fertilization is how that happens right um differentiation is not how you have different possible Gene combinations differentiation happens uh when you're actually developing and you you start to form your own organs cloning is false because cloning produces direct copies of one another and differentiation say for the same reason is false right so fertilization is is correct would be correct because that's how you um that that's when a mom a mother and a father DNA would mix together during fertilization meiosis would be correct because that's that's what leads to sexual uh reproduction which is what you need to even initiate fertilization and mutation is correct because mutation is the way that you have random changes uh in in DNA so uh moving on to number 30 it says that all the genetic information necessary for the growth and development in a sexually reproducing animal is present in what well here we need to grow and we need to develop right so it's not going to be egg cells or sperm cells right if if the question was what is necessary for us to reproduce what is necessary for an organism to reproduce a passage genon yes you need either sperm cells or egg cells or egg cells or sperm cells right we what we they're asking for is growth and development and that would be zygote a zygote is is a diploid it's a diploid cell that forms after fertilization right after fertilization occurs so and and a zygotes then would develop into a fetus sorry an embryo and then a fetus and then actually living uh creature right so um in order for development you need those two copies oh you need that combination or those 46 chromosomes 23 from your mom 23 from your dad you need them to combine during fertilization to form a zygote or or fertilized cell from which you can develop and differentiate it too all right so that was the entire video uh if you have any questions please let me know in the comments below