Speciation by Geographic & Reproduction isolation - Grade 12 Life Sciences evolution

Hey there wonderful matrix, welcome to educate, today we'll be doing the topic of speciation under evolution. I hope that you have watched my previous two videos explaining the concept of the sources of variation, explaining natural selection, Lamar theory and what not. Now we are now looking at the term speciation. Basically speciation is the formation of new species. So when we are forming new species, we say that the speciation occurring. You need to understand first, what are species? You remember that the definition of species, we've said that this is a group of organisms that can interbreed. So the most important thing is that they can interbreed and they're able to produce fetal offspring. So they're able to produce fetal offspring. So if we have got two organisms, two similar organisms, and they're able to mate or they're able to produce some fetal offspring, then we can say that those are organisms of the same species. For example, as humans, we are organisms of the same species because we can interbreed. I can interbreed. I've definitely interbreed it in my life and I've produced fetal offspring. So basically that's a species. But basically we can actually form new species from old species using this technique known as speciation. Speciation can be achieved in two ways. That is, we have got two types of speciation. We have got speciation by geographic isolation as well as speciation by reproductive isolation. Now when we say that we are having speciation by geographic isolation, it simply means that we are actually separating a population using a physical barrier. We are still going to see how that works, but basically we use a physical barrier or a geographic barrier to separate a population. Then suddenly we create new species. So we need to actually know how does this work. For example, in this picture, you can see that we have separated these animals from these animals. You can see that they're almost, they look alike, right? But we have separated them using a river. So this is a geographic barrier. So they cannot meet anymore because we have separated them. So how do we end up creating new species from old species? Does it always mean that when we separate two organisms, then they are no longer the same species? Now let's look at speciation by geographic isolation. So basically when you say that we have got speciation by geographic isolation, we start with a population which has got a single species. So we start with a population, remember a population is just a group of similar organisms as well that are of the same species. So basically we start with a population that is single, and then it becomes separated by a geographical barrier. A geographical barrier is just a physical barrier. For example, a sea, a river, a mountain, or a lake. So usually it's a sea, it's a river, a mountain, or lake is most probably one of these four can come out in a scenario. So basically we can split a population into two using that geographic barrier. For example, look at this, we are having here, these two organisms, I don't know if they are crocodiles or whatever that are, those are, but basically we have separated them using this river. You can see that this is sort of like a river or it's a stream. So these two organisms, they cannot meet with each other anymore because we have separated them. Okay, so that's the first step in speciation by geographic isolation. We separate a population into two using a geographical barrier. It can be either a sea, it can be a river, it can be a mountain, or a lake. So you can see that on one side of the river, on one side of this stream, or on one side of this river, we have got one part of the population, and on the other side, we have got another part of the population. So we have separated them. So now how does that make them different? Now the next thing, there is no gene flow between the two populations. So basically, once you separate these two populations into two, then there will not be any gene flow. Remember, we're not talking about gene flow, it simply means that the organisms are mating or they are interbreeding. Okay, they are doing the deed, yes, the deed. So basically, if these organisms cannot meet, then they cannot do the deed, okay? They cannot mate, they cannot, there won't be any gene flow. Gene flow simply means that they are mating, they are interbreeding, that kind of stuff, right? So basically, because we've separated them using a sea or a river or a mountain or lake, these two cannot meet. For example, you can see that this one definitely wants to meet with this one, I can feel that they want to meet. But because we have got this barrier of this river that we're having between them, they cannot meet with each other. So there won't be any gene flow between these two populations, okay? So now, each population will now be exposed to different environmental conditions. So you need to know one thing in geography, that on two sides of a river, we can experience different weather conditions. Let's just assume that this population on this side of the river, they're experiencing sun conditions, it is a warm area, or maybe there's a good temperature. And then on the other side of the river, on the other side of the geographical barrier, they're experiencing cold conditions. So you can see that the moment we split or the moment we separate the population into two parts, each part or each population will now be exposed to different environmental conditions. So it simply means that this side of this population may be experiencing hot conditions, they may be experiencing warmer temperatures, or maybe cold conditions or whatever. And the other side will be experiencing different conditions. So they're exposed to different environmental conditions. And once they're exposed to different environmental conditions, then we know that natural selection will okay to both of them. So basically, natural selection, it occurs independently in each of the two populations. Remember, we've said that natural selection just simply means that the survival for the fittest. Okay. So for example, if I have gotten a little that can survive hot weather condition, then I will leave. But if I do not have the favorable characteristic, I will die. That's what natural selection simply means. Simply means that the organism that has got a favorable characteristic, it will leave and it will pass on that characteristic. And the organism that does not have a favorable characteristic, it will die and everything's over about it. But now here, natural selection, it will okay independently in each of these two populations because they are exposed to different environmental conditions. So for example, let us just say that these organisms on one side of the river, they're exposed to sunny conditions. So it means if natural selection was to happen to these organisms that are exposed to warmer temperatures and sunny conditions, the ones that have got the favorable characteristic will live on and the ones which do not have the favorable characteristic, they will die. So please make sure that you watch my video on natural selection as I explain how it works. But basically, you can see that here on this side, the ones that can survive the hot weather conditions will live on, but the ones that cannot survive, they will die. And on the other side, let's just assume that on the other side of the river or on the other side of the geographical area, they're experiencing extremely cold conditions. The ones here that have the favorable characteristic to survive those cold conditions, they will live on. But the ones which do not have the favorable characteristics, they will do it. They will die. So basically, that's what we mean when we say that the natural selection will occur independently. So natural selection will occur on both sides of the organisms. So it means it's just the survival of the fittest. So it just simply means that on this side, we will remain with those ones which can survive the hot weather conditions only. And on this side, we'll remain with those ones that can survive the cold weather conditions. Because remember that the fact that they're experiencing different environmental conditions, the ones that have got the favorable characteristic, the ones that can survive the conditions, they will live. The ones that they cannot survive those conditions, they will die. So natural selection is occurred independently. So this will actually lead to these two different individuals, or two different populations to become different from one another. Definitely, they will be different. Because remember, we said that on one side here, the ones that will survive are those ones that can survive the warm weather conditions, or maybe the high temperature weather conditions. And these ones on the other side of the river, they survive the cold weather conditions. So they're already different from one another. Remember, these were the same population and we separated them. But because of this separation, they experienced different environmental conditions. Some of them were experiencing warmer temperatures. Some of them were experiencing colder temperatures. All right. So the ones that will survive on this side will definitely be different than the ones that will survive on the other side. Because remember that natural selection, it will just keep the ones that have the favorable characteristic. So here we'll have those animals that have survived the hot weather conditions. On the other side, we'll have the animals that have survived the colder weather conditions. So basically, now we can say the individuals of these two populations are now different from each other. And not only are they going to be different phenotypically or in their phenotype or in their physical characteristics, they will be also different genotypically. So they will become different from one another phenotypically and genotypically. It means that they will not have the same gene structure. And you'll be like wondering how. Remember, I've already said that the ones that have the favorable characteristics, they will live on. So it means that if I was to look at the gene of one organism on this one side, the gene will be able to survive the hot weather conditions in that environment. But if I was to take another one on this colder side, its gene will be able to survive the cold weather conditions. So you can see that they're now different from each other phenotypically and genotypically. So basically, they are now different. They are now different, these two populations. That's why you can see here they are depicted using different colors. Some of them here, they are white, here they are a bit darker. But they came from one population. Remember, the aim here is to create new species. Now we've separated them. Now, even if these two populations were to mix again, they will not be able to interbreed to produce fertile offspring. So basically, now let's just assume that the river is gone or maybe the river has dried up and these animals are now able to crawl up to each other or they are now able to meet or mix with each other. They will not be able to interbreed. They will not be able to interbreed to produce fertile offspring. So if I was to mix them, let's just say the river is now dry, like in this image that I'm pointing. Now the river is now dry. So now you can see that these two species, these two parts of the population, we are now mixing them again, maybe after several years. But now they are different from each other. Remember, they are different from each other genotypically and phenotypically. That's why you see some of them are black, some of them are white, depending on the environment that they are coming from. So now if we mix them together, they will not be able to interbreed to produce fertile offspring. Even if they interbreed, they will not produce fertile offspring. Yes, it's fine. Maybe they can mate or maybe they can love each other and mate and have some fun and whatnot. But still, they will not be able to do it. They will not be able to produce fertile offspring. So they are already different species. So we can say that these two populations are now different species. Because once you are not able to interbreed to produce fertile offspring, then you are not of the same species. Remember, we have defined species to say that they are similar organisms that can do it, that can interbreed, that can mate with each other, that can do the act and get some fertile offspring, some fertile baby that can do the same thing as well. But now these two, when we mix them again, after separating them, after they've experienced natural selection, after they have now been differentiated genotypically and phenotypically, now even if you mix them, they will not be able to produce fertile offspring. Even if they mate, they will not produce fertile offspring. So now we can say that now we have got two different species, because if they cannot produce fertile offspring, then they are not of the same species. It's like you are taking a human being and you are mating. Okay, that's weird. Basically, you're taking two different organisms. Even if you interbreed them, they won't produce fertile offspring. So now we have created new species through the method of geographic isolation. So when you say that we are doing speciation through the method of geographic isolation, it simply means that we separate a population. Remember, there were one population. It was a single population. We separated it using some geographic barrier. In this case, it was a river. It can be something natural, okay, because you can see that this is a river that has separated them. And then now, what happened? There was no... Okay, they were split into two, and then there was no gene flow between these two populations or sub-populations. These two parts of the population, there was no gene flow. They were not able to interbreed. So there was no flow of genes from one individual to another individual. Now they are separate. And then now, each population, remember, it is exposed to different environmental conditions. We assume that on one side of the lake, it is hot. On the other side of the lake, it is a bit colder. So basically, they're experiencing different environmental conditions. Don't say weather conditions, environmental conditions, all right? And then now, natural selection occurs independently on them because they're experiencing different conditions, right? So it means on this side will only remain with those ones that can survive the warmer conditions or the hotter conditions. But on the other side of the lake will remain with those ones that can survive the colder conditions. So natural selection has occurred to them independently. So, okay, and then now, these individuals are now different from one another phenotypically, genotypically as well, because they are surviving different conditions, right? These ones are surviving the sunny conditions. These ones are surviving the colder conditions. So basically, they are different. They cannot be the same, okay? They cannot be the same. So basically, now they are different from each other, genotypically and phenotypically. So it means their gene structure is different from one another. And also, the way they look is now different. You can see that here they are white, here they are a bit brownish. But at first, they were all the same. And then now, even if you mix this population again, whenever you want to mix them, let's assume that the river is no longer there and they're able to meet with each other. Even if you mix them, they will not be able to interbreed to form fertile offspring. And then now they're different species. So we have done speciation by geographic isolation. Okay, so by the way, please join the private tutorials if you want extra help. We have got great tutors that are able to help you online. Just simply WhatsApp this number, only say the words, Hi, I want to join private tutorials. Guys, I'm married. I don't want any, any silly conversations on my WhatsApp. Thank you. Hey, Lapo. I know that you've been enjoying this wonderful video and most likely you've been enjoying watching this handsome face in front of you. But sorry, ladies, I'm taken. I just here to tell you that educate is on the road to 100,000 subscribers by the end of 2025. So please click the subscribe button and click the notification bell so that you get notifications whenever I post new videos. I want you guys to pass. Okay, so if you make my dream true, I reach 100k subscribers. I will make your dreams come true. I will even get you to varsity. I will get you with seven distinctions. Yes. So now let's look at the reproductive isolation. Remember, I've said that at first, the speciation has got two methods. So I remember we mentioned it's that speciation has got two methods. It can be achieved by geographic isolation. The one that we've explained whereby we put a physical barrier, then we separate the populations and whatnot. And then now the other method is the reproductive isolation. So now let's talk about reproductive isolation. Basically, when you're talking about reproductive isolation, you want to prevent reproduction. So how can you prevent two animals from reproducing with each other? Not using any physical barrier or anything like that. But basically, is there any way nature is preventing certain organisms from producing with each other? So let's look at those mechanisms that are known as the reproductive mechanisms of a reproductive isolation mechanism. So now here we have got breeding at different times of the year. So basically, when you've got two organisms that are similar to each other, or maybe they probably can interbreed, or maybe they can even form fetal offspring. They're actually the same species. But if they breed at different times of the year, let us just say that I have got lions. Okay. So some of these lions, they breed in summer. Some of these lions, they breed in winter. Okay. Winter is the ideal one. But basically, some of these breed in summer. Some of these, they breed in what? In winter. So we can see that they are breeding at different seasons of the year or different times of the year. So we are actually preventing them from doing what? From reproducing. So that's one method of reproductive isolation. Reproductive isolation is not really much about anything. It's all about preventing the fertilization or preventing reproduction between two organisms. So in this case, breeding at different times of the year, it prevents the species from mating with each other. Okay. A lion that reproduces or that breeds in May cannot breed in September. So in September, it will be just gaining energy and whatnot. But in May, it will start breeding. So basically, if we have got a male lion in May, when it meets a female in September, it will definitely not breed with her. Okay. They'll be just like looking at each other and look like, I will see you next year. But basically, breeding at different times of the year is one of the methods that we use to do that to prevent reproduction between two species. The other mechanism is the species-specific courtship behavior. Look at this image. You can see that these birds are dancing to each other's tune. So basically, each and every species, they've got specific courtship behavior. When we talk about courtship behavior, it's the behavior that attracts the male. All right. So basically, let's assume this is the female because I think she's the one in front. Yes. Yeah. So this is the female. You can see, but basically, this is the female. You can see that she is dancing in a certain way. So that's a certain behavior that will attract this male. So you can see it will only attract this male and no other males. So if we take any other birds that can be of the same species or the same kind, some of them will not be able to resonate to this dance. So each and every species, they've got specific courtship behavior. They've got a certain way that they behave with each other to attract each other so that they can fertilize. Okay. So basically, it's a mechanism that is isolating them from fertilizing with other males. This female can only be fertilized by a male who likes a dance. Okay. So basically, it's a specific courtship behavior. It's a behavior such as a dance. You can see sometimes the birds, they have tunes. Birds like singing and singing to attract the males. That sound, it can only attract a certain type of male and not the other males. So basically, it's a way to isolate themselves. It's a reproductive isolation method. We also have got a plant adaptation to different pollinators. You know this from Great Living that each and every different types of plant or flower, it is pollinated by different agents. Okay. Some of them are pollinated by birds. Some of them are pollinated by wind. Some of them by bees and all that. And all those insects and whatnot. So basically, each plant is adapted to different pollinators. So it makes it isolated. You will never see this plant being pollinated by a bird. No, it is only for the insects. You can see the bird actually likes the red colored flowers. Most of the times I'm not mistaken. And then we also have got infertile offspring. The best way to express this is taking a donkey. If we have got a donkey, here is a donkey. And we mix it with a horse. You can see that a donkey and a horse, they're almost the same thing. It's always the same. It's almost the same thing. But now, when they mate with each other, they can produce an offspring. But that offspring is infertile, right? So the offspring or the combination of a donkey and their horse is known as a mule. Okay, whenever you hear the word mule, we are talking about the word, the combination of a donkey and a horse. So basically, they reproduce a mule. But a mule is infertile. It can never fertilize with another mule to make more mules. No, a mule is infertile. I know, like literally infertile. It cannot make more babies. So this is a creation of a new species. Okay, we are creating new species, remember? So it's a creation of a new species. So a mule cannot mate to produce any fertile offspring. A mule will just remain the way it is forever and ever. Okay, so basically, when you combine a donkey and a horse, we produce an infertile offspring. That's a way to create new species because a mule is a different species. Definitely cannot interbreed with a horse. If this mule was to try and mate with this horse, that would be just a disaster. Nothing will happen. So it is infertile offspring. Then the last one is a prevention of fertilization. This one is a bit hard to explain because it needs you to have a bit of a dirty mind. All right, so basically, there are some methods that can prevent fertilization. Remember, fertilization simply means that the sperm cells and the ovum, they are meeting with each other. They are fusing with each other. Their nuclei are fusing with each other to form a zygote and later on, whatever. But there's no true protection. But basically, there are ways to prevent this fertilization. So basically, animals, they don't use contraception like humans do. But basically, there is a natural contraceptive method, something like that. So prevention of fertilization is one of a reproductive isolation method. The best example of this is the organs that don't fit into each other. So you will probably hear, maybe just read Understanding Life Sciences. You will try to understand that. So basically, it can happen that the female has got an opening that does not fit, such that the male cannot fit into her. In that sense, that sense is the right one. So that is also one of the methods or one of the mechanisms of reproductive isolation. It can happen that the female is like this, but the male is like this, something like this. So definitely, they cannot fit into each other. So thank you so much, Matrix, for watching this video. Don't forget to subscribe to the channel. Tell your friends to also stay tuned.