CSEC Biology Marathon

追加: 2026-05-14

[00:00:07]Okay. So basically we're going to be talking about natural selection and genetic engineering. This is a part of section C continue continuity and variation that is a part of the C biology syllabus. So basically this is just a small section or basically just a small portion of that part basically. So we're going to be going in depth on natural selection and also genetic engineering and we're just going to be comparing both of them seeing what's the difference. What's the principles behind both of them and overall what's the purpose of natural selection and genetic engineering. So, let's just go and get into that. So, before we get started, go ahead and check out the free resources right here. Um, you can go and get free content on both channels right here. You have the CSC study guide and then you also have tutoring right here which this one is paid or there's a fee but basically it is available if you want to email tony [email protected] if you need tutoring but this um these are free stuff and this is also free stuff so you can go ahead and utilize both of them right so let's get into it so when we're talking about any topic at all literally just any topic, we have to first define it. And that is exactly what we're going to be doing. We're talking about natural selection and we're also talking about genetic engineering. Before we even get into it, right? If like if I look back at my high school days, before we even get into what anything is, just the name alone kind of give you a hint of what both of these are. When you hear natural selection, you're thinking natural. When you hear genetic engineering, just the word engineering alone, you know that engineering means that we tamper or basically there's some human involvement in order to make something work. Once you hear the word engineering and you know what genetic means, we're talking about genes when we talk about genetic. So, let's backtrack. Let's start with natural selection. And if nothing else stands out to you, the word natural should literally tell you that it's untampered. It's by nature. We humans don't play a part in natural selection. It is literally natural. It happens by nature by God. It we don't tamper with it. That's the that's the clearest thing. So if you ever go into the exam and you don't remember what the actual definition is, the name itself, dissect the the name, it's called natural selection. What does it mean to select something, to pick something naturally? That's basically what natural selection is. And basically the definition that we have here is saying that it's the process by which organisms with favorable traits are more likely to survive and reproduce pass on those traits to the next generation. What is that telling you? Basically what this is telling you is that in nature only the fittest of the fittest are going to survive. So if you are fit and you are healthy, you are you are likely to live a long life. If somebody else they they get sick a lot, they have a weak immune system. They're probably going to die.

[00:03:49]So basically that's the principle behind natural selection. It is saying it is the survival of the fittest. The ones with the most favorable traits for their environment are going to survive. So let's just say that you live in a particular environment that it it it benefits a particular organism to be small. They have to be small. It's not going to work out at all. Right? Or if you're if you're or if it's another type of organism and they have to be big because it benefits them to be big. So that's the principle behind natural selection. It means the survival of the fittest. So it's almost like a race.

[00:04:31]So the person if we're having like a normal sports day race, you have two people lining up at the starting line, one of them is probably really short.

[00:04:40]And that no means say um the person necessarily cannot run fast. But we do know that people with longer legs have an advantage more than other people. So basically both are at the starting line and one has longer legs. Now the person with the longer legs they actually have an advantage right that necessarily means they have a win but they already have an advantage to winning because they take bigger steps than the person who has short legs. So basically that's the principle behind natural selection.

[00:05:17]It's talking about the organisms that have the most favorable traits and are likely to pass on those traits to the next generation. Because if this per if this organism they have long legs, it makes sense to have long legs for them and it it's a favorable trait. When they have kids, those long legs are going to be passed on. It's just a survival of the fittest kind of situation. So it's it is all geared towards the environment. So just get that natural selection. That is what it means. Survival of the fittest.

[00:05:56]Then now we're talking about the role of natural selection in evolution.

[00:06:00]So evolution is just such a big topic that they have been researching and researching and researching and even right now it is not completely it is not completely researched. There's more research to be done right and basically evolution speaks to the change the change in populations over a long period of time. So, we're looking back from humans coming straight up when they used to say, "Oh, we we were monkeys or apes or whatever we evolved from, right?

[00:06:36]You know the history. Go back and check the history." But basically, they say that we evolved and became homo sapiens.

[00:06:44]That's the um human species right now, but evolution essentially, right? So it's basically the change um in population over a period of time, a long period of time. So we don't mean last week. We don't mean last year, we don't even mean 10 years ago. We mean like 100 years plus basically, right? A very long time coming straight up. That's what evolution talks about. Now we know that natural selection is a driver of evolution. What does that mean? If natural selection is a driver of evolution, we're saying that it has an impact on the next generation essentially because if evolution is a change in population over a long period of time and we said that natural selection affects evolution, we mean that it affects it in the way that only the fittest of the fittest are going to survive. So if you have 100 organisms and is only 10 of them in that population have the the favorable traits then is only the 10 going to survive and the other 90 are going to die and it's basically that 10 are going to reproduce and then their offspring are going to also have the favorable traits that they had right and there's some trick to this but we're not going to get into that yet or I don't think at this level right but basically Ally natural selection affects evolution because it is picking the fittest persons. It is picking the most favorable traits to pass on to the next generation. And that next generation is going to be the next population that's that's there. The individuals in that new population are going to be made up from from essentially the parents, right? So the parents natural selection picks the favorable traits. Those parents survive, they have kids and in turn it does affect evolution because it's changing the population, right? 1 million years ago or however long, 1 million years ago, having let's just say for example, having short legs were advantageous 1 million years ago. And then a million years later, because natural selection influenced it, now short legs are not favorable. So it's now long legs. just for example purposes only. So basically the role of natural selection in evolution we're saying that it selects individuals with favorable traits. It increases the survival and reproductive success. It causes beneficial traits to become more common.

[00:09:20]Exactly.

[00:09:22]That's basically what I was saying just now. Because if you have 100 people in a population and only 10 out of the 100 have those favorable traits, the 90 are going to die because the environment is working against them basically. That 10 that did survive, they are going to reproduce and then their offsprings are going to have the favorable traits that that 10 did have basically and that is what is going to cause these beneficial traits to become more common. So basically the next generation is going to be made up of only favorable traits and what can happen is that you know you have dominant and recessive genes. Let's just say somebody that they had the favorable trait but they have they had the recessive um alil for something else and that's probably the only way for something else to become reintroduced into the next population or some catastrophe. some natural disaster happened or some other external factor can affect the population. Why there is not only beneficial traits but basically there's a lot to it right but don't worry about that right and it also leads adaptation to the environment yes so basically um in that population with the same 100 only 10 of them had the long legs right only the 10 of them and the other 90 it never work out for them sense and those longlegged people they are more adapted let's just say that all let's just go back to like maybe Adam and Eve days you know the garden and let's just say this is all just example purposes but let's just say that all the trees were very tall and it only makes sense because back in the day you know you don't have stove and all that stuff you have to be tall if you're going to pick fruits and you need fruit to eat and all that stuff so basically it was advantageous just for example purposes only right and then we know as I said before, it drives evolution and it forms new species. So natural selection will always pick the fittest of the fittest to pass on those genes. Right? So it is one of the major drivers of evolution.

[00:11:46]Now what are some advantages of natural selection? We say it promotes adaptation to the environment. It increases survival and reproductive success.

[00:11:57]maintains or improves the population fitness and we talk about fitness a lot and we say if you don't remember anything else about natural selection just remember that it is a process by which it selects or it picks the fittest of the fittest in the population right so every individual is held to that standard of being fit so it's not like oh the entire population is going to be healthier or the entire population is going to be fit no it is done by individuals So it is the survival of the fetus almost like when um reproduction takes place or when um a woman gets pregnant. Let's just say all the sperm smell the sperm cells all of them rush towards the egg and you know that only one will actually fertilize the egg. So think of it like that. The fastest one to get to the egg is going to be fertilized. That is natural selection right there. So the sperm the sperm cells a lot of them are produced but only one can actually fertilize the egg and actually get the woman pregnant basically. So you have to look at it from that perspective. So that's an example of natural selection right there. Just always remember it is done by the survival of the fittest. And as we said before, it drives evolution and it drives speciation and it eliminates harmful traits over time because natural selection only deals with favorable traits. That's it. If it's harmful, if it's not beneficial, natural selection will get rid of it.

[00:13:41]What are some disadvantages? So it's a very slow process and as we said before is like natural selection is not a yesterday it's not a last week it's not last year it's not 10 years ago it takes many generations many many many many generation it's not a quick process is a long time coming from caveman days coming straight up that cannot make up evolution and we say that natural selection is a major driver of evolution it's coming all the way up from then.

[00:14:16]And another disadvantage, it says it may may not keep up with the rapid environmental changes. And this was the point that I did not really want to get into, but since it's here, what this is basically meaning is that the environment is not constant. So 1 million years ago, your ancestors having a particular trait was beneficial. 1 million years ago. As we said before, let's just say short leg, long leg, let's just say that back then we said that short legs were they were not a good trait to have. It never make no sense. And so only the tall people survived basically, right? And actually let me use a real world example um with Darwin's pinches. So is not constant.

[00:15:08]Meaning that let's just say for example um let's just say for example way way back let's just say that you have the population of birds and basically there was a drought. So let's just say there was a drought and you have the finches and so it made sense that the finches finches are birds. So basically it made sense that they had hard tough beaks in order to crack the seeds like the seeds that came from the tree, right? And that was the selection that was natural selection at work. And so basically these birds, they evolved to have these tough hard beaks because there was a drought at that time. And so it made sense to have those um broad and tough and hard beaks in order to crack the seeds basically, right? And basically that is what natural selection chose for that population. And the birds that had short and like soft beaks, they weren't able to crack this the seeds and basically they starved and they died.

[00:16:22]And this is actually a real life um story. I think it was Darwin. I don't remember what experiment it was, but this is actually something that really happened. And but you can definitely go and look it up and see which experiment this was. But basically natural selection picked these tough hard beaks because at that time there was a drought affecting the population of birds and and basically it made sense that the survival of the fittest the ones with the soft beaks they died or most of them died and it was mainly the ones with the tough hard beaks those were the ones that lived and then down the a flood happened and when that flood happened the seeds became softer and then natural selection ended up um bringing back the soft beaked um birds basically. So basically those soft beak birds they started to dominate again basically. But basically we're trying to say that natural selection doesn't always keep up with rapid environmental changes because it's it's such a slow process because when the drought happened, natural selection was like okay only the only the big the the birds with the big beaks the tough beaks that can crack the seeds they're going to survive. we pick those because they could actually feed themselves, right?

[00:17:56]And then the other birds that were not so their beaks were short and soft and couldn't couldn't um chew the seed like the other birds. Natural selection ruled them out and basically a very small small small um population probably survived or maybe not at all. And then some years down the line something happened and natural selection has to bring back those soft beards. So basically that that's what we're trying to say that natural selection doesn't always keep up with the environmental changes because natural selection is so slow. So while it was there picking the tough hard beaks and those who were having offsprings and those having offspring they did not realize let's just say for example 10 years later there will be a drought. They had no it had no idea that okay you know what there's going to be a drought and we need to select another trait that selection is basically slow it lacks basically. So that's what we mean by that. Um, another disadvantage, it can lead to extinction if organisms cannot cannot adapt. And that actually goes back to the same story or the same experiment I was trying to um bring back to that. If those and as I said before, majority of those birds with the soft short beaks, the most of them died. most majority died because they could not feed on the seas because their beaks were not strong enough. So it can lead to extinction of a particular species if they cannot adapt to that environment.

[00:19:48]Um another disadvantage favors only trace beneficial for survival not necessarily for other purposes. Okay. So this can really mean that natural selection will pick the trees for survival. So it doesn't take into consideration something like let's just say um let's just say that some organisms are able to camouflage right and camouflage camouflaging is very important for many many animals like they need to camouflage in order to protect themselves to hide from predators and all that stuff. So they needed that. And then there are some other animals. There are some other animals that do not camouflage because they use their pretty colors like maybe um the peacock or I don't remember which other animal right now, but they they are not hiding because they use those pretty colors. You have some birds that they sing and all kinds of stuff basically that would make them noticeable by predators all for the sake of um sexual reproduction. So basically they need they needed to mate. So natural selection doesn't care about mating or it doesn't it doesn't care about um sexual reproduction. So that's what it kind of this is what it means basically.

[00:21:13]it's only really focusing on survival.

[00:21:16]It's not focusing on oh you need to mate and reproduce. So that's basically what it means. And then another disadvantage is it reduces genetic diversity in some cases because if you have two um let's go back to the bread example.

[00:21:36]Some of them had hard tough beaks. Some of them had soft, short, not strong beaks. And if they get rid of the not strong beaks and only going to leave the ones with the tough hard beaks, then you know that that's less diversity because all of them in the population are going to have the same thing. Or even if we go back to the long legs, short legs, if we ruled out if natural selection p selected against short legs and now everybody have tall leg, everybody have long leg now then that's less diversity.

[00:22:10]The population is going to basically look the same.

[00:22:14]All right. So we talked about natural selection already. Um migration is very simple. It's another driver of evolution. It's basically when um a species or population moves from one place to another and then you have mutations change in a DNA um sequence. You have genetic drift which is completely random and it causes changes in al frequency. So basically these four are driveways of evolution.

[00:22:46]They can affect how the population will look later on down the line.

[00:22:51]And so yeah then you have artificial selection. So basically artificial selection or selective breeding is a process in which humans select the desired trait to pass to the next generation of offsprings of plants or animals. And this is what I was talking about before. When we're talking about natural selection and artificial selection and even genetic engineering from the name artificial selection, you kind of know what this is already. You hear natural. You're thinking about nature. You're thinking about God.

[00:23:28]You're thinking about untampered. When you hear artificial artificial selection, you're thinking about tampering. You're thinking about we maybe we as humans need some tweaks. We did something because it's artificial.

[00:23:42]It's not I won't say it's not real, but it's not natural. Basically, so we are the ones that pick the traits that we want to pass on to the next generation.

[00:23:52]In natural selection, nature does that.

[00:23:55]We play we play zero part zero role in natural selection. We cannot um we can predict natural selection to a certain extent but we cannot interfere with it or tell natural selection to do this or to do that. It happens naturally over a long period of time. Artificial selection let's just say that we have um let's just say we have an example here with the cows. So let's just say our cows we get a certain amount of milk per day from the cow, right? normal cow would grow the cow, have the cow and everything, right? But then we as humans, we're like, "No, we have factories, we need to supply them.

[00:24:36]People need cow's milk, people need skin, people need all types of milk."

[00:24:40]And then you say, "Okay, we need more production from um the cows." And then we artificially change something within the cow in order to get higher production. Even with chickens, we said that the chickens, they lay some eggs. I always say, hm, we need more eggs for production for mass scale. We have the factories and we need to sell it to the supermarket and everybody need this, this, this, this, this. And so basically, it's us tampering to get the desired treat that we want so we can pass it on to the next generation, right? So if you want larger eggs or if you want more milk, artificial selection can be done in order to get that.

[00:25:28]This is just comparing artificial selection right here talking about its advantages and it disadvantages.

[00:25:38]So basically one it produces organisms with desired traits and basically we are the ones picking the trait. We say, "Okay, the cow we need, we need more milk." So, we're the one putting in the tree that we want. Increases, increases food production. As we said before, if we get more egg, if we want more milk, natural selection can help us to get that. And then it says improves disease resistance in plants and animal. So, yes. So, basically, selection is not only about producing food for the market or getting more milk or getting more eggs. It's also about keeping the keeping animals, plants and animals healthy because let's just say that um let's just say that there is a particular illness that affects um these types of animals and we're trying to build up resistance in them. Then artificial selection is a way for us to get rid of the undesirable trait. We don't want the co to get sick. We don't want to go to get um this particular illness because dental kind of slow slow everything. So basically that's what this means right here. We can improve disease resistance. It can also enhance the quality of products and in all of this is basically us editing. We're tampering or tampering for the better if you get what I mean. And it also helps develop new breeds or varieties. Then we have disadvantages of artificial selection. So basically the thing about even artificial selection and also natural selection we spoke about it is that when it comes to selecting anything it means choosing and because you're choosing to enhance this particular trait it means you're getting rid of variation. you're getting rid of differences between um the individ the individuals or the offsprings or the animals, the plants. We're getting rid of that diversity essentially. Um so that's what's happening because we're trying to enhance just that particular traits and we don't want the bad traits.

[00:27:49]So, but guess what? Those bad traits or those undesirable traits make up a part of what genetic um variation is. any type of variation, the good, the bad, everything that is diversity when everything is different.

[00:28:05]Um, and then we say that it can increase susceptibility to certain diseases. So basically, we can get disease resistance, but we can also become more susceptible depending on what within the animal they're tampering with, what they're changing, what they're altering in order to get those traits.

[00:28:26]other diseases, it does put them at risk of um developing another type of disease depending on the method that they use um sterilization everything. So it's a two-way street.

[00:28:42]Um another disadvantage is may cause undesirable traits to appear. So basically um artificial selection it's it's not natural. We know that and none of us are God. We cannot predict things.

[00:29:00]Basically, all we're working on is research. That's what these people work with. They work with research that have that has been previously published and that's how they come up with their theories or their hypothesis and say, okay, this can work, this can't work.

[00:29:16]And the thing about artificial selection is that it's as far as I know it's fairly new. As in I mean that there's more research to be done even on genetic engineering. There's a lot more to uncover and dive into because as I said there's no way to predict. We don't know anything for 100%. We're not 100% sure about anything. We know to a certain extent what could happen, but we don't know 100%. We don't know how each offspring or each individual or each animal or plant will react. We don't we're working on previous research and we kind of just winging it honestly, right? So, let's just say they did artificial selection and something can go wrong and undesirable trait pops back up.

[00:30:09]The next thing about artificial selection is that it requires time and human effort. Time and human effort. And what I believe and then the last one says it can lead to inbreeding problem.

[00:30:22]So basically I believe that it's not everything that can be tampered with should be tampered with. Some things we should leave alone because sometimes we don't know what we're putting together or what can happen. and basically requiring time and human effort. It is literally called artificial selection.

[00:30:44]So it means that it is basically humans.

[00:30:47]We're doing all of this basically, right? Inbreeding is basically um when you meet individuals like siblings or cousins but basically related in some way and it it can cause problems depending on what they're trying to do or what their end goal is when they carry out this artificial selection.

[00:31:12]So this is just a table comparing them.

[00:31:15]Um natural selection long and slow.

[00:31:18]Artificial selection is very fast.

[00:31:21]Natural selection there's more variation in the population.

[00:31:26]Um artificial selection not much variation in the population. Natural selection reproducing individuals have characteristics that suit their environments.

[00:31:37]And then artificial selection those individuals have characteristics that are desired by us humans. Natural selection there's less likely to be inbreeding. So offspring are healthier.

[00:31:51]Artificial selection there's more likely to be inbreeding. And the chance of getting genetic disorders because just in general, not even just with animals, but it's a general rule of life that it's almost like like mating with somebody from the same family. And there's a reason why there's ethical reasons why you wouldn't want to meet within your family or anybody you're related to. Ethical reasons, right?

[00:32:21]Spiritual, religious reasons, a lot of reasons. But from a genetic perspective, it's also very risky because you're mixing like with like and you don't know what will happen. Basically um natural selection is natural in the wild and artificial selection we play a huge role. We are the basically the authors. We're the engineers behind it in artificial selection.

[00:32:51]Now we're getting into genetic engineering. And basically this is where we're getting into the nitty-gritty basically. And it's basically us altering the DNA of an organism to change its traits or produce new characteristics and engineering.

[00:33:10]Listen, when we say genetic genetic engineering, it means to make, we're going to construct, we're going to we're going to alter. That's what this means.

[00:33:20]And we're focusing on the genes.

[00:33:23]Right? The gene is a segment of DNA.

[00:33:28]So what are some advantages of genetic engineering? Produces crops with higher yields. It creates animals with desirable traits. It helps in reproducing medicines and vaccines.

[00:33:41]It can correct genetic disorders in humans. It reduces the need for chemical pesticides. There are a lot of benefits to genetic engineering. But at the same time there are risk there are concerns.

[00:33:55]There are spiritual concerns, religious concerns, ethical concerns in this not just genetic engineering but also artificial selection. Right?

[00:34:07]So basically they you're basically there's a potential to reduce genetic diversity.

[00:34:17]And the second one and this is actually a big one can have unforeseen health or environmental effects. And this is the part that a lot of people are concerned about because genetic engineering it is relatively new as in there is a lot more research that needs to be done on this because because they're just starting to do this genetic engineering. It's not like it's been around for millions and millions and millions of years so we know what's going to happen. No, it's literally a new science, a new technique that they're bringing in. And so when you're altering DNA and you know that DNA that's DNA is unique, right? The our DNA sequence.

[00:35:03]It's unique to every individuals. That is us tampering with our cells. It it's it's just a complex thing, right? And if you go back to like maybe high school biology when they say that cells are the basic unit of life um it's basically it's basically a lot like nothing is more unique to you than your DNA your DNA sequence and then this genetic engineering is literally altering that DNA sequence right as in DNA sequence that God gave you this genetic engineering is altering and nobody knows what's going to happen in a 100 years.

[00:35:49]Let's just say they alter a a human's um sequence or they change up something in the genes. Um they use a particular technique and let's just say they use maybe crisper or one of those other molecular biology techniques and we don't know what's going to happen in a 100 years time to that human body.

[00:36:12]That is kind of why most of these studies are actually carried out on animals first, right? It's mainly carried out in animals. And I think they're used on humans but not as frequent, right? Because they can be um used in basically like helping with cancer and other things. But there are ethical concerns people I said before ethical, spiritual, everything. Nobody knows about the future, no one knows what's going to happen. And if we're talking before, if we're talking from like a spiritual perspective or um a religious perspective, it's like, as I said before, there's nothing more unique about you than your DNA.

[00:36:59]Your DNA is your DNA. No one shares the same DNA as you. that that is the most personal thing about you that make you up basically right and it's okay so basically yeah um there are concerns about that um it's also very expensive and it requires advanced technology it requires um advanced expertise meaning people who actually know their stuff experts in their fields So it it requires a lot basically. Um there's also the potential for creating new allergens or toxins. So we honestly the bottom line the biggest disadvantage about genetic engineering is that we do not know what we're tampering with.

[00:37:50]We're kind of just winging it. Previous research has been done. We have a little hypothesis. We have a little theory. We okay it could go like this. We see that it can help but we don't know the full extent of what can happen because of this basically. So that's the downside to genetic engineering.

[00:38:11]Right? So we went through artificial selection, natural selection, genetic engineering and these are part of section C of the cet biology levels. So let's just you can literally go back and look at each slide. We did not go in depth on this. We don't need to go in depth as long as you know what they are that they're of evolution and you can define.

[00:38:41]Okay. So now we're moving on to variation and basically variation is a part of section C continuity and variation is a part of that um section of the syllabus for CE biology and basically if you need free resources they are right here.

[00:39:02]you can go and check out those channels and the email is also right here and the study guide is right here.

[00:39:14]So basically um we're talking about genetic variation and this is such a term that we use so often and in the simplest form when you talk about genetic variation we're talking about the differences between the genes differences in the DNA among individuals within a population or a species.

[00:39:38]So basically we're focusing on differences. That is key behind genetic variation and it's very important for us to have variation for a multitude of reasons. And overall it's just better for survival when the population is not all the same and the population is different. And the number one way to get some variation is simply from sexual reproduction. Cuz you know that asexual reproduction gives you clones. All the offsprings exactly alike. Variation on the other hand gives you a variety. It gives you diversity. Everyone in that population or in that species have a unique thing to them. Even though they are related and they they look almost alike but they are not all the same and it's almost like siblings or within a family you have siblings and you have one that may be tall then one short then one medium height. So variation is very important for survival.

[00:40:48]So basically when genetic variation is present in a population individuals they are not genetically identical which leads to differences in traits such as their height, skin color, um disease resistance or behavior. So basically what that means is that even if on the outside they look alike, genetically they are not the same. No two people who are products of sexual reproduction are the same. Basically their genotype if you remember what genotype is and basically genotype is the genetic makeup of an organism. The genotype is always it's it's different right? So, it's different from the phenotype because you can have two individuals that look exactly the same on the outside with the same phenotype and then when you check their genotype, their genotypes are completely different. One might be um dominant and then you might have one that is hetererozygous basically. So, you won't know until you check the genotype basically. But we're saying that genetic variation no two are genetically identical.

[00:42:08]So basically how does um variation arise? So basically I said that the number one way is through sexual reproduction and basically we're going to get down with it more and see the different ways that we can get some variation in our jeans basically. So one way we have mutation right here and mutations do happen obviously they happen somewhat frequently but not all but most of the time when mutations happens they don't they don't change much if that makes sense not all the time and basically mutation is a change in a DNA sequence now sometimes when this happens you know that it can cause serious problems such as people who end up with cancer and that's simply because of the change in their DNA sequence right so sometimes you can have um I don't remember the term but basically you can have the within a codon and basically we're talking about your DNA sequence but in the simplest terms things can change in your DNA sequence something one of the nucleotides can be swapped out and everything stays normal and then in some cases it can be swapped out and then it causes a lot of problem right so genetic variation does come from mutation and we said that those are changes in the DNA sequence and they can create new alles then we have miosis and we know that miosis only happens in sexually uh sexually reproducing organisms Right? Just like how in cell division we saw that mitosis happens in somatic cells, meiosis only happens in sex cells basically. And there are two important processes within meiosis that occurs to allow for this variation and that is crossing over. If you remember, you have meiosis one and meiosis 2. In prophase one of meiosis one, you're going to have crossing over. And that's basically when the sister um the sister chromatids or is actually the homologous pairs.

[00:44:37]They're going to switch um segments and that allows for basically recombination and that's how you get those little variation. Then you have independent assortment and that happens in metaphase one and that's basically when the chromosomes are lining up at the equator when they're lining up in the middle of the cell. Basically the rule is that they don't line up at the cell in any particular order if that makes sense.

[00:45:07]They they just line up completely randomly. And so by the time anaphase happens where they're pulled to opposite end of the cell, they're pulled like all over the place because they did not line up in any particular order and that allows for some more um variation, some more differences in the offsprings. Then we said um sex reproduction comes genes from two parents we need offspring and sex reproduction and meiosis both of them kind of just go together if that makes sense because they are intertwined essentially because meiosis can only happen if sexual reproduction is happening basically. And then you have gene flow which is basically the movement of individuals between populations and that helps to introduce genes you also have random fertilization.

[00:46:00]And the example that I would give is that during conception when a woman gets pregnant, you have lots and lots of sperm cells, but only one will actually fertilize the egg and only one will actually get the woman pregnant. That's also random fertilization. So it's not predetermined that okay, this particular sperm cell is going to fertilize the egg. We have no idea which sperm cell is going to move the fastest and get to the egg first and fertilize it. So that's where we talk about random fertilization.

[00:46:36]So what's the importance? Why do we need all of this variation? Why do we need all this differences? What's the purpose behind all of this basically? So it's very important to adapt to changing environments. It's important for disease resistance. is important for evolutionary potential. It prevents ingredient problems and it ensures population survival. So basically if we put all of this in a summary, the importance of genetic variation is to increase our chances of survival because disease resistance we can resist disease and you don't get sick or whatever you're going to live. If you don't have ingredient problems, you're going to live. So the goal behind genetic variation is to ensure that in a population at least some will survive because let's just say that the entire population is there let's just say the entire population let's just use plants and say that we have some plants that were produced from let's just say asexual reproduction they're all clones all of them look the same and something happens a particular disease comes in and because they are all the same disease, the disease is going to wipe all of them out one time, all of them dead. Versus if you had some plants that they did sexual reproduction and now some of the plants are disease resistant, some are not, the disease come and the ones that are not disease resistant, they die. And then the ones that are disease resistant, the meaning that they're healthy and they're good, they survive. So that's the whole point of genetic variation to ensure that basically to ensure survival or ensure that some survive from the offsprings that are produced basically.

[00:48:28]Then you have um two types of variation.

[00:48:31]Um you have continuous and you have discontinuous variation. So continuous variation is basically one that shows a gradual change in the differences with no clear categories. It is usually influenced by many genes and environmental factories. Example man height.

[00:48:54]So if you look at this little chart, it's showing the gradual change. So you can see that it goes it starts off low then go up again down and the prime example of this would be woman height.

[00:49:10]So it's basically a gradual change with no clearcut categories. There's usually no clearcut categories in the situation.

[00:49:21]Then you have discontinuous variation and discontinuous variation has clearcut categories with no interbing. So basically this means is either you are or you aren't. This is either you have it or you don't. So in continuous variation we're talking about it there was room for ambiguity meaning that somebody can have height. Somebody might be 51, 52 or 5 this 5. But point is that there is room for there's no clearcut category to say okay you have to be this or you have to be that. With this with discontinuous variation there is clear cut categories meaning blood groups for example meaning that is either your A b or o there's no aish there's no bish there's no abish. you have to fall into one of the categories basically. Um even with your gender, you have to either be male or female. There's no in between.

[00:50:21]There's no issues. Either you can roll your tongue or you can't. Either your um ear loses are attached or they're not attached. There's no in between basically. And if you look at the graph, clear cut category. This is showing different blood groups, but clear cut categories.

[00:50:40]If you look back on continuous variation, this is it wasn't it was more curvy, it's more it wasn't defined.

[00:50:49]Basically, it's not defined.

[00:50:52]While in this continuous variation, it is very much defined clearcut categories.

[00:50:59]And then this is literally a comparison table showing you continuous versus discontinuous variation. Um just going back to it, discont discontinuous has distinct categories. Continuous has no distinct categories. Examples of um continuous variation. You have height, weight, heart rate, finger length, leaf length is no clear categories. And then discontinuous is either you have it or you don't. There's no in between.

[00:51:30]There's no is either you have blue eye or you have um black eye. There's no in between. Basically, the bed groups is you have to fall into one of the categories. Versus with continuous variation, you don't have to fall completely into a category if that makes sense. So, you can be for example weight, you can be maybe 150, 150.5.

[00:51:54]It can be like maybe 150.6. You can be in between if that makes sense. And then the graphs are represented very much differently with the continuous variation showing a bell curve while discontinuous variation showing clear distinct categories.

[00:52:13]All right. So basically that's um variation right here comparing continuous and discontinuous variation talking about importance how it arises what it is and yeah so all right so the endocrine system so basically we're going to look at the endocrine system and just look at the different glands look at what it is and just the processes that are taking place within the endocrine system. And we're also going to be comparing it to the nervous system. And basically the nervous system and the endocrine system.

[00:52:58]They they have a little relationship. Let's just say that. And we're going to be comparing the endocrine system to the nervous system.

[00:53:08]um for free resources. You can just go ahead and check those out right there.

[00:53:14]And then you also have the email for tutoring down at the bottom right here.

[00:53:21]Um these are lessons and you can get more free resources here. And this is the study guide that you can find on here as well as the rep study method as well.

[00:53:36]Okay. So the endocrine system so basically it is a system of ductless glands that produce and release hormones directly into the bloodstream to regulate and coordinate the body's function. So that means that there are no ducts, there's no tube, there's no vessels, it is just released directly into the bloodstream, right?

[00:54:06]And basically the endocrine system uses what we call hormones. And hormones are basically chemical messengers that are used to transport these different messages around the body essentially, right? So the endocrine system produces hormones and those hormones travel directly into the bloodstream. The hormones are the chemical messengers that tell the body exactly what to do depending on the gland that is coming from whether it be the the pituitary gland, the pineal gland, the adrenal gland depending on the glands because the glands are what makes up the end system. What is going to be produced is the hormone. So hormones are produced from glands and glands make up the end system.

[00:55:00]And when those hormones are released, they regulate and coordinate the body's function. So if it means increasing something, decreasing something, controlling the blood sugar, it it's all works together to simply maintain homeostasis in the body basically.

[00:55:19]Now the differences between the endocrine and the nervous system is that one one main difference is that endocrine system uses hormones basically, right? So hormones are what are produced in the endocrine system and in the nervous system what we have instead is um neurotransmitters.

[00:55:39]So basically neurotransmitters are the chemical messengers in the nervous system and then in the endocrine system.

[00:55:46]Hormones are the chemical messengers.

[00:55:49]The endocrine system uses glands while the nervous system uses nerve impulses in order to transmit the message along the nerves.

[00:56:02]The nervous system is also a lot lot faster like like um have if you've ever heard of the all or nothing um theory or whatever but basically all or nothing means that that's basically when a neuron fires if it meets the threshold it will fire and it will generate the message and it will travel along the neuron in order to get the response.

[00:56:29]So basically the hormones are carried in the blood and for the nervous system they simply use electrical impulses and those travel along the nerves and those are what produces those rapid short-term responses.

[00:56:46]Now based on the endocrine system we know that there are different glands and some of those glands are the penal gland, the pituitary gland. So basically the pineal and the pituitary gland both of both of them are found within the brain within in that region basically you have the thyroid in the throat and then the thigh muscles below the thyroid the adrenal glands are found on top of the kidneys and then the pancreas is basically in between and then of course you have the ovary which is in the reproductive area.

[00:57:27]So basically um each gland produces a particular hormone to stimulate a particular function basically. So depending on the gland a particular hormone hormone specific to the function of that gland will be secreted basically and we know that the pituitary gland is very much in the brain. Thyroid in the throat and the parathyroid glands behind the thyroid gland. So if we look here the parathyroid gland is behind the thyroid gland right here. The panic as we said before adrena overies all that stuff. So basically you can see where the locations are within the different um glands and where they are in the human body. And then if we look at the hormones now, so basically one of the easiest ones to remember are basically the pituitary gland and that one's found in the brain and then you have the pancreas. And the reason why the pancreas is so significant because everyone kind of knows about blood sugar. We know about insulin.

[00:58:47]um people who have diabetes and you know that insulin, glucagon, they all play a role in regulating the blood sugar basically. So when it gets too high you know insulin is produced when it gets too low we um we secrete glucagon which basically brings back up the blood sugar level basically. So there are different hormones and you probably won't remember all of them. But yeah, you just have to at least remember one or just remember the the basics behind it. But panic, so insulin glucagon, that one is also very popular on the exam. They like insulin, glucagon, they always bring up the blood sugar. So that's popular. The pituitary gland because it's the master gland, controls basically all the other glands within the body. That's also very significant. So it would be good to know the pituitary gland. So we can have the growth hormones and as you can see the function this one is a major one. It it has a growth hormone, the follical stimulating hormone, luteinizing hormone. It it does a lot. This one does a lot. And you have thyroxine, the thyroid gland. And basically all of them are very much significant and all of them play a very big role in the different functions. So basically with the gland they all secrete a very specific hormone and they all serve very specific function.

[01:00:30]Then exocrine and the endocrine gland.

[01:00:33]So basically this is pretty simple.

[01:00:36]Endocrine endocrine glands those are the ones that release the hormones directly into the bloodstream. That the very first thing that we said was that the endocrine glands we said that those are duckless meaning that they are released directly into the bloodstream. There's no vessel there's no duct. They are just released directly into the bloodstream.

[01:01:00]exoprene they release these substances through the ducks. So that's basically one of the major differences. So one is duck lifts and one is not one has ducks. Um the chemical messengers of the endocrine glands. Then we have the exoprene glands talking about enzymes, mucus, sweat, saliva that produces. You have all of those as part of the exoprene glands and different target areas, different speeds, different functions and very different examples. So basically there's a difference between endocrine and exocrine glands but ex exoprene the function is not necessarily on the exocrine it's more on the endocrine glands because these these are the more I want say the more important ones but they're the more these are the focus basically the focus is on endocrine and the most they will ask is just compare and just maybe mention what's the main difference between both of these, but this is the focus basically.

[01:02:15]Um, so yeah, so back to the different glands.

[01:02:20]Um so basically blood sugar that's a very popular one as I said before and they love insulin and they love glucagon because this is something that's very popular especially for people who have diabetes because the insulin is going to lower the blood sugar and the glucagon is going to raise it. Um, if we're talking about water balance, then you have the pituitary gland producing ADH. And ADH increases water reabsorption in the kidney and it prevents dehydration.

[01:02:58]Thyroxine and adrenaline both of them help to regulate temperature.

[01:03:06]Um, those in it involves both the thyroid and the adrenal glands. It increases the metabolic um activity and heat production and overall maintaining homeostasis. For basically all of these processes right here, the goal is simply to maintain overall homeostasis in all of them. Even if it's a different process, the goal is simply always homeostasis in all cases.

[01:03:34]Then you have the metabolic rate. Um you have thyroxine and that is produced by the thyroid gland and it basically control the speed of re chemical reactions in the cell and it basically just to regulate the energy use overall.

[01:03:57]So if we're looking at an example negative and positive feedback. So basically negative feedback we're basically reducing the original stimulus to maintain balance while positive feedback is enhancing the stimulus until a specific event is completed.

[01:04:23]Right? So if the thyroxide levels are going to rise, the pituitary gland reduces TSH and that's the thyroid stimulating hormone and overall it's just to reduce it. Basically as we said before negative feedback we want to reduce it in order to get homeostasis.

[01:04:47]Positive feedback we want to increase it to get homeostasis. And the positive feedback one is a little bit different because if we're looking at child birth and oxytocin is what's released during um child birth and that it basically increases in the body in order to get more contractions basically and the whole point is to get the baby out.

[01:05:14]So the whole point behind oxytoxin, we're increasing it in the bloodstream.

[01:05:20]We're causing more contractions. The baby is going to be delivered and therefore the body can go back to homeostasis once the baby is out.

[01:05:29]Basically, that would be positive feedback. So we're just comparing them.

[01:05:35]Negative, just remember that it reduces the stimulus. Positive increases the stimulus. And that stimulus is basically the hormone that we're talking about in this case, right? And overall the goal behind the end system, the interior system is to always maintain homeostasis. So it's meant to use these hormones either to increase or decrease the levels within the bloodstream, but the goal is always homeostasis.

[01:06:10]Okay? So basically this is another past paper that um we're going to go through.

[01:06:16]So basically this one is taken from um 2020. So basically it's the same instructions. It just says this paper consists of six questions in two sections and all that stuff. So basically you should actually read the front page just in case things change.

[01:06:35]Always read the front page for the different instructions. But now let's get into the real questions. So all right. So basically obviously they cannot test you on the entire syllabus but they will pick out different different parts and put it on the paper two. So anyways this is going to be section A. We're going to start here and then we're going along. So the first question is saying so basically this is a diagram of a diseased artery.

[01:07:07]So what do we know about arteries?

[01:07:09]Arteries um they carry blood away from the heart, right? So we know that so it carries blood away from the heart at high pressure. So now it's asking um identify the condition shown in figure one. So obviously what we see here is an artery, right? So it brings blood away from the heart at high pressure. And what we have here specifically that's going to tell us what kind of disease is the plaque. So as you can see the plaque literally build up and basically plaque is like a mixture of um different different things like for example like cholesterol and all that stuff that gets stuck in the arteries and it can cause this condition right here called athetherio sclerosis.

[01:08:01]we cannot pronounce it but this is the condition right here. So this is the condition that causes a disease arteries and basically where we have plaque um building up as you can see it's a build up because regularly or naturally the blood is supposed to pass through right because artery is a blood vessel. So now when you have this plaque it's blocking the blood flow and can lead to this disease right here. So this would be the answer for um number one.

[01:08:32]The second question is saying describe how the condition in figure one contributes to hypertension. So this plaque being within the artery is literally obstructing blood flow. Right?

[01:08:45]So obstructing blood flow and it's going to increase resistance and when the blood is having a harder time moving through it is going to raise the blood pressure. So that's how we get hypertension.

[01:08:57]Hypertension is the same thing as high blood pressure says the exact same thing. So if you see the word hypertension don't be alarmed.

[01:09:05]Hypertension and high blood pressure is the exact same thing. It's just um high blood pressure is just like um layman term or just regular term but the medical term is hypertension for high blood pressure.

[01:09:20]All right. So now it says next person says name one potentially fatal cardiovascular event that the condition in figure one may lead to. So the very first one can be a heart attack. And how we know that it's heart attack? It's the most obvious one. First the question is saying cardio. From you hear the word cardio you know it has to go with the heart. And if we go back to the arteries, we know that arteries bring blood um away from the heart, right? So it's a blood vessel. So basically um it can lead to a heart attack because what will happen is that the blood is supposed to um leave the heart and obviously go out. The blood is going to be blocked and it can kind of like cause a backflow, you know. So it can lead to a heart attack if the blood is not flowing and regulating how it's supposed to. So that is how that condition can be a heart attack for um this um diseased artery.

[01:10:25]Then the next question states state two factors other than diet for developing the condition in figure one.

[01:10:35]And the reason why they say other than diet is because obviously we know that cholesterol if your cholesterol levels are high and stuff like that it can lally build up and start to block um within the blood vessels right. So that is why they so they scrapped um diet completely. So we cannot mention anything anything about any cholesterol or any fatty food or nothing like that. So it means that in this situation the other risk factors for developing the condition is going to be high blood pressure and also smoking.

[01:11:06]So basically high blood pressure the same hypertension. So if somebody already has um high blood pressure, right? So let's just say that they don't have this um disease, right? But they have high blood pressure. So the fact that they have high blood pressure, it kind of is like a risk factor, right? So it increases their risk of developing the condition. So having high blood pressure it would cause um uncontrolled so uncontrolled high blood pressure would damage the blood vessel right increasing the risk of athetherio sclerosis right so increase the risk and then also smoking. So smoking when you smoke it would kind of it would contribute to damaging the lining of the arteries promoting plaque buildup and also increasing the risk of heart disease. Right? So these are two other risk factors that you can mention other than diet cholesterol or like that um causing the plaque to build up in the blood vessel.

[01:12:08]So you can mention these two high blood pressure. If the person already have it before then they're at risk of potentially developing this condition and also if they are a smoker then it can also helps to um um damage the lining of the arteries and also lead to this condition. So those are two risk factors that you can consider.

[01:12:31]Right. So now this question is talking about um there's a menu. So basically it says individuals with heart disease are advised to follow a special diet to improve their condition and overall health. From the menu below circle the healthiest option for each meal time which would contribute to improved cardiovascular health. So this is a very easy one because you can literally just use your common sense and look at it and see which is the healthiest out of all of these.

[01:13:06]Right? So you have breakfast, you have lunch and then you also have snack. So if we look at the first column with breakfast, right?

[01:13:16]So basically where the x's are that is what the answer is. So never circle it but there's an x there indicating that that is the answer. So, white bread and butter and hot cocoa. We're going to um scrap that one completely, right? We're going to scrap that because it's not the healthiest choice. You know, butter and fat and all that is not the best um choice. Add cocoa, especially if you put sugar in there, that's al that's not the best um choice because what we're trying to do is to improve the cardiovascular health. So, anything with too much cholesterol, too much fat, we don't want it, right? So, we're going to scrap um white bread and butter and hot cocoa, frosted flakes and milk and banana. On a first glance, it seem like said that would be healthy. But you see, frosted flakes is processed, right? So, then probably put sugar and all kind of something in there. That is why we're not going to choose frosted flakes, corn flakes, and milk and banana. The answer is going to be oatmeal with fruit and herbal tea because it's the most naturalist and it will promote the best um cardiovascular health. That is why that is the answer for lunch. The cheeseburger one will scrap it completely. That is not healthy. That's cholesterol and that is just leading to a heart attack, right? Because it's not healthy to build up in your blood vessels and can cause heart attack and stuff like that. your fried chicken, colelaw, macaroni and cheese and lemonade. That one also sounds very appealing. But fried chicken, cholesterol, the aisle, it's not good.

[01:14:54]So, the best option for lunch is going to be grilled fish, right? We get the protein. We have rice, fresh green salad, string beans, and a glass of water since you know sugar don't good for us. So, that is why that is the answer. And then dinner slices of pizza could never be the answer just on first glance. And then also peanut butter and jelly and white bread could not be the answer either. It just it could not be the answer. Too much um stuff in there, processed stuff. So the best answer would be fish soup with vegetables, right? Because when you're talking about cardiovascular health, like I said before, we're trying to get rid of oil and just overall fatty fats. like that's what's going to um cause the plaque to build up in the arteries and stuff like that and we don't want that. So that is why we cannot have those as the answer and the answer is going to be fish soup with vegetables.

[01:15:52]For the snack section, it's very obvious potato chips processed stuff that candy bar too sweet. So it's best to go with the mango which is natural. So that is going to be the answer for um the snack one.

[01:16:07]Then right so basically it says figure two shows a graph of the leading cause of debt during the years 1900 and the year 2000 right so basically um this is 1900 this is 2000. So basically it's saying what percentage of the deaths in the year 2000 were likely caused by non-communicable diseases. So first we're going to have to look on 2000 since that is what it asks for. So basically heart disease that's so first what is an uncommunicable disease? So basically it's a disease that cannot be passed on.

[01:16:46]So for example if you touch somebody then cannot just get it right. So that is what they're asking what percentage were caused by communicable disease. So the first one up here is heart heart disease right. So basically if somebody cannot just get heart disease just because they have it. So that's um non-communicable. Colon cancer, that's also non-communicable. Cardiovascular disease, we cannot just touch somebody and then get it. That's also non-communicable.

[01:17:13]COPD, that's also non-communicable.

[01:17:17]And then pneumonia and influenza. This right here, this is communicable. So for example, if somebody have the flu and you go around them or you touch the same things as them, then you're likely to get the flu. And pneumonia can also be contagious.

[01:17:32]Um then diabetes mel melus is also this is noncommunicable.

[01:17:38]So non-communicable non-communicable non-communicable non-communicable communicable and then noncommunicable again. And then accidents are not necessarily considered diseases. So we're not going to count it in it. So basically, if we want to find out the percentage of deaths in the year 2000 that were caused by non-communicable diseases, we are going to have to add up all of these, right? We're going to add up heart disease, colon cancer, cardiovascular disease, COPD and diabetes, melitus, and it's going to come to about 70%.

[01:18:16]Now we cannot add pneumonia in it because it is communicable and then also accidents are not considered diseases right so we won't add that in it either right so that's going to be the answer for that then it says outline the most significant difference in the types of diseases that resulted in death in the year 1900 as compared to 2000. So if we go back up here, we realize that in 1900 these are most of them are infectious diseases, right? Meaning that you can get them from people, right? So for example like small pox you know that can can be contagious. Um you go around them you might get it your morning you might get it. Diarrhea these things can be um transferred to somebody else. Especially if you go around them that is why we say infectious diseases. So some of them are in fact communicable versus in 2000 where most of them are done communicable. Literally the only one that is communicable is the pneumonia and influenza from the 2000 list while over here smallox diarrhea pneumonia all of these things can be um infectious to other people. So that is why that's the answer. So 1900 had more infectious diseases than in 2000.

[01:19:41]Right? So then it says suggest two reasons for the difference in the types of diseases outlined in C that's C2.

[01:19:51]So too different for the difference in the types of diseases out in C. So basically um what can be the difference in the types of diseases within the two years is perhaps better educated public. So for example, if people are now um better educated and understand that okay, if somebody have diarrhea and you you share things with them or eat the same thing, you might catch it. If you go around them or let's just say somebody who um have gastroenteritis or something and vomit or it can be transferred or if somebody have pneumonia, it can be contagious or have flu. People understand and are more cautious now because they're better educated. And the next reason is also um more accessibility to health care. So more health care is more healthare and treatment is more readily available. So it's able to be um controlled a lot more. So for example, if somebody might um get pneumonia, they can seek um health care, they can go to the hospital. Um people just overall know how to better handle these infectious diseases now, right? And if anything wrong they have the health care system.

[01:21:12]So basically it would not cause as much death. So for example if you look at the 1900 you had if you look at the 1900 you had a lot of people dying from these different infectious diseases. Now in 2000 less people are dying from infectious diseases because they have more access to healthare. So instead of somebody just wait for dead they can go to the hospital and actually get treatment and that would cause a decline in u people dying from infectious diseases. So that would be the answer for this and then the number 2 a. So it says list four characteristics of living organisms. So this right here is a very easy question right. So with the four that I picked it can be growth, reproduction, excretion and movement.

[01:22:02]But basically we know that there are seven um characteristics of living organisms that's growth, reproduction, irritability/ sensitivity, movement, excretion and then also um nutrition and respiration. So if you pick any of the seven it would be um correct. Right. Now B said two organals found in plants that are not found in animals. So basically a chloroplast is very unique to plant cells and also a cell wall is also unique to a plant cell. You could have maybe put large vacule because you you'll only find a large central vacule in the plant cell and it's not found in animal cells also. So that could be a possibility.

[01:22:54]Okay. So now the next question says Sanjay carried out an experiment to confirm that oxygen is generated from photosynthesis. Figure three shows his experimental setup. And then basically this is the procedure right here. Right?

[01:23:10]So basically they want to test basically to find out if oxygen is a byproduct of photosynthesis.

[01:23:19]And you remember the formula. The formula says um carbon dioxide plus water. Sunlight over chlorophyll gives you glucose and oxygen, right? Because you get oxygen from plants. So once you know that, this should be pretty simple and straightforward. As a matter of fact, I think we did do this. You're supposed to do it in your labs.

[01:23:41]All right. So now state which experiment A or B that would have generated more bubbles.

[01:23:48]So, experiment A would have generated more bubbles and the reason for that is experiment A had a light source. So, if we go back to the photosynthesis formula, um basically experiment A had a higher light intensity, right? because we don't know how the room the room that the experiment was carried out in. We don't know how the room was, but all we know is that um experiment A had a higher light intensity. So that means that it was getting enough light in order to carry out photosynthesis, right? So if we know the formula, we know that um light is a necessity for um photosynthesis to take place. So they need light.

[01:24:34]So now the next question says state what Sanj would have observed happening to the glowing splints in experiment A and experiment B. So basically in experiment A because um the plant is photosynthesizing a lot right? So since the plant is photosynthesizing a lot it is going to be producing a lot um more oxygen bubbles right. So the bubbles will be coming up. So now when um Sanjay would have taken out the test tube and put the stick in there or whatever right the splint the splint would basically glow would kind of have like a fire right so that is what would happen and the reason make me feel like me jump it so that would happen the splint will glow and then in B when the splint go in there the splint would not have any fire would not have any glow basically All right.

[01:25:31]And then we're going we're going to explain why.

[01:25:36]So then it says identify the gas that would have produced the bubbles in experiment B and state the process which have produced the SC. So for experiment B carbon dioxide would have been produced and the process would have been respiration.

[01:25:51]Now the next question that followed so CO2 is a gas and then the process is respiration. The next question says explain why Sanj can conclude that oxygen is a byproduct of photosynthesis.

[01:26:04]So basically in experiment A when um he put the splint in the test tube right and it had that fire or that glow right.

[01:26:14]So basically that glow only happened because oxygen causes combustion right so that is the reason why the splint glowed slash had a fire um in the test tube is all because the presence of oxygen was there. So if there was no oxygen or not enough oxygen in there because the plant was not um photosynthesizing enough then the sprint would not grow would not glow there would be no fire um there would be no light basically and in state which um experiment served as a control and give one reason for your response. So B was what served as a control and this is because there was no manipulative um variable. So basically we were kind of not testing for for anything in a sense with B because in A we had a light source. So we could see that okay um we can see how the plant responds to having the light intensity and everything like that. So basically the control would have been B and that would be because there would was no manipulative um variable.

[01:27:22]All right. So the next part is going to be the endocrine system. So the endocrine system has literally everything to do with glands and hormones, right? So the first part is saying identify the glands labeled A and B. So from your see the A pointing in the brain, we know that that is going to be the pituitary gland. And then from we see B pointing on top of the kidney, we know that is going to be the adrenal gland, right? And these are probably um two of the most common glands that everybody might remember out of all of them. Kidney adrenal adrenaline and then pituitary brain. Right.

[01:28:06]So now complete the table by inserting the missing hormone or hormone function.

[01:28:12]So LH luteinizing hormone stimulates the corpus lutium to produce pole. This is what they have already. But the part that they want us to answer is efficacy.

[01:28:24]So the function is to promote growth of um follicles and production of estrogen in the ovaries. So basically this is the follicle stimulating hormone right that would be the hormone for here and then the adrenaline is what would initiate that's the hormone that would initiate fire or flight um response in the body just overall preparing the body for action and increases the heart rate and the blood flow to the muscles. So, for example, if somebody realize them in a danger or maybe they're getting attacked, adrenaline would be what would be released. That would initiate that fight or flight response within the body and just start bring up your heart rate and sending more blood flow to the muscles.

[01:29:13]Then it says outline one difference between the endocrine system and the nervous system. So the endocrine system and the nervous system um kind of work very closely to each other. But since they said difference um endocrine system the biggest difference is that the endocrine system utilizes hormones while the nervous system uses nerves/neurons right so nerve cells. So they use nerve cells/neurons to transmit signals. So basically the endocrine system releases hormones within the bloodstream and then the nervous system uses um neurons to send messages all over the body. You know you have your motor neurons, sensory neurons, all of those things and then hormones is a different situation.

[01:30:00]Another difference between them is that the endocrine system is very slow. So obviously because these hormones are being released in the bloodstream it means that they are moving very very it's moving very very slow. So we know that our body has blood in it, right? So for example, if um a hormone is released in our bloodstream, right? So oh actually this is the biggest one. This is another difference. So basically with the nervous system, it has a target, right? So for example, if um maybe we have a sensory neuron or something, maybe we touch something or whatever and it's going to send that message um to the inter neuron and it's going to get to the brain. So basically the nervous system is a lot more precise. With the endocrine system, when that hormone um gets released into the bloodstream, it goes all over the body. So, for example, if if um let's just say maybe um let's just say maybe the adrenal hormone or whatever, right? But and basically the target is for it to um I don't know, let's just say it releasing in the body and it has a target. So if we release a hormone in the body and it has like a target because of the bloodstream it's going all over the body but it will only act where it's supposed to. If that makes sense. If that makes sense. But basically the endocrine system is very slow because it's going in the bloodstream. So it's going all over and then the nervous system is a lot more precise and a lot more faster.

[01:31:38]Hopefully that makes sense. Just follow what's um here. Don't even bother with me. Just follow what's here. This is a lot more simpler.

[01:31:46]So anyways, next question. So Rhonda is a 53year-old wife who is experiencing challenges with her weight and is feeling unwell. The doctor suspects she might have a thyroid problem. The table before shows the results of Randa's blood test.

[01:32:06]Okay. So based on the table so this the endocrine condition that Ronda may have.

[01:32:13]So basically this table is showing us the test thyroxine and thyroid stimulating hormone. So normal levels for thyroxine should be between 4.6 to 12 and then for the TSH the normal level should be between 0.5 to 0.6. Right? So now we have Ronda's levels.

[01:32:36]So runners levels is 1.8 and then 0.55.

[01:32:42]So basically what we're going to look at is the tyroxine part here. So basically this is saying that if if the value for the patient is less than 4.6 that is what is saying if it's less than 4.6 and she has 1.8 it means that they have hypothyroidism.

[01:33:06]If their if her value was greater than 12 then she would have hyperyroidism right but because her value is less than that the answer um is going to be hypothyroidism right so anyways that's the answer identify the lab data from the table that supports the diagnosis of the endocrine condition and it's the same thing that I was explaining so less than 4.6 six and she has a 1.8 so she's less than 4.6 and that's what um makes her have hypothyroidism.

[01:33:42]Now the next question says treat three conditions or three symptoms that Ronda may experience as a result of the conditioning B.

[01:33:52]All right. So then this question says state whether Ronda's condition is caused by a malfunctioning pituitary gland and then give one reason for a response. So basically the pituitary gland is what controls all the other glands. It is referred to as the master gland, right? So if um anything was wrong, we would a would be we would be able to trace it back to the pituitary gland. So basically give one reason for your response. So basically we say no, it's not the pituitary gland that is malfunctioning.

[01:34:27]And how we know is because the thyroid stimulating hormone is in the normal range. The thyroid stimulating hormone is what is released by the pituitary gland. Right? So if it was the pituitary gland that was malfunctioning, this value would not be in a normal range. So let us go back up and look Rhonda's levels for the thyroid hormone.

[01:34:51]It is 0.5 which is within the normal range. So that is how we know that the pituitary gland is not malfunctioning right that is how we know right here.

[01:35:04]So as we said before if um it if the pituitary gland was the problem we would know since it is what secretes the thyroid hormone that gets the thyroid um gland to work. But in Rhonda's case it's in the normal range. So that is not the issue. So the next question says the doctor has prescred a hormonal replacement drug and as a result Rhonda has lost 5 pounds. However, she's unable to lose any more weight. Suggest whether the doctor should increase her dosage and state one reason for your response.

[01:35:42]So basically no basically. So um the hormonal replacement drug that Rhonda was given right is mainly to just fix her symptoms right so it's just to fix her symptoms. So when someone has hypothyroidism, it basically means that um yeah there are fatigue, tiredness, all that stuff comes with it, right? And that is because it affects um the metabolism, right? So taking this replacement drug, the focus or the aim is really to fix the metabolism.

[01:36:22]So run.

[01:36:26]So basically that would be the answer.

[01:36:28]The drug is already fixing her metabolism and she cannot lose any more weight. So what's the point of increasing the dosage right once the symptoms are fixed and the reason why um medications such as this one is because it affects the metabolism. So what can happen is like water retention is what would cause her to like um gain weight.

[01:36:51]So them increasing she taking this drug her metabolism increasing that is why she's losing the weight right. So no we wouldn't need to increase the drug.

[01:37:07]All right. So next up this is going to be cell division. So cell division is very simple and straightforward. So cell division promotes growth and reproduction in organisms and these processes occur by mitosis. So we have two types of subdivisions. We have mitosis and also miosis. But based on first glance this question is targeting specifically mitosis. And just to know the difference is that mitosis is basically to repair ner cells and stuff like that while miosis is specifically targeted to our sex cells. So the division of our sex cells is miois and division of like our somatic cells or body cells. Um those are um done by mitosis. So basically the first question identify one cell in the body in which mitosis takes place and one cell in which mitosis does not take place. So basically mitosis takes place in somatic cells. Somatic cells is just the same thing as body cells, right? is just a fancy name for our body cells. So um cells that mitosis take place in would be like our muscle cells, skin cells, cells like that. And then another cell the type of cells that you would never ever ever see mitosis happening in is in our sex cells, right? So like our egg cells and our sperm cells, absolutely no mitosis can take place there. only meiosis cuz miosis is the designated process. It's a designated um cell division to divide those sex cells and not mitosis.

[01:38:45]Right? So now let us look at um the process down here. So process of miosis, right? And we said that um so at the end of mitosis we're going to end up with um two daughter cells. At the end of miois we're ending up with four daughter cells, right? So we're going to start off deployed and then we're going to end hloid in mucosis. So it says match um label state of the cells with the description by placing the correct letter A, B or C on the line. So if you completely clueless just you need to remember that mucosis the end result is going to give four hli do cells. Four hide do cells. You see the four hloid daughter cells at the end of miois right here. So when we see hloid we know that c is going here immediately and then we know that the starting point we started off with deployed. So we started off deployed and that's what is a and in here common sense would tell you that this is you lally see divide you start off with four and now all of them have appeared. So you can literally use a command and say okay DNA duplication takes took place right here and that's it. So applied this C deployed A and then B is going to be DNA replication.

[01:40:08]So then it says state one factor that would account for the variation in daughter cells at the end of meiosis because we know that when at the end of meiosis every sing the four daughter cells that are produced they are different. None of them are alike. And this is because of two processes. Even though this question only answer for one, but there are two processes that takes place during miosis. I like miois does the lap twice. So it's basically mitosis but done twice and a little tweak to it, right? So you know that in mucosis we have like homologous um homologous chromosomes coming together and all of that stuff, right? So one the factor that would cause variation meaning cause them to be different just like how human beings at the end we're different like you and your brother and your sister is not the same each person come with their own different tweak. You could have look alike all the while but everybody come with a little tweak and it's because of crossing over. So during prophase one crossing over takes place that is basically where um the chromosomes kind of swap um a piece of a piece of like um the gene. So that's crossing over right at the signups and then you have independent assortment that would take place in metaphase one.

[01:41:28]So basically independent assortment it just mean that the chromosomes are just line up completely randomly at the equator. So that's when that happened.

[01:41:37]They're going to just line up at equator completely 100% randomly.

[01:41:42]Right. So this that is basically what we're going what we um go through and hopefully this is useful and um we can say is good luck and hope everybody do good on their exam.