 You may have heard of things like man is evolved from apes or maybe something like birds that evolved from dinosaurs. But what exactly is this evolution? And what causes it to happen? Well, in this video we're going to learn exactly what this evolution is by taking a much simpler example. So evolution can be defined in many ways. I like to think of it as change, it's a change in something called the gene frequency. Gene frequency and we'll talk about what this is in a second. Of a population, of a population over, over generations, over generations. Okay, so a lot of fancy words over here, right? So to make sense of this statement, let me tell you a story of beetles and crows. So imagine there are some red beetles on a bush who like to eat these leaves and there are some crows over there which like to eat these beetles. And so as these crows eat the beetles, their number decreases, but these beetles reproduce. And that keeps the population in balance. So everything is fine and great until one fine day a green colored beetle is born. And it's a little difficult to see, so here is that green beetle, alright? Now you may be wondering, hey, how come suddenly a green beetle gets born? This can happen due to something called mutation. Mutation is where the genes that are being passed along from the parents to kids undergo some changes. Because of these changes, some new traits are found in the kids. So maybe the gene that is responsible for color underwent some change and because of that the new kid got green colored. These mutations happen all the time. A realistic example is blue color of the eye that we see in humans. That is also mutation. So that happens all the time. And if you're wondering why green color, it's purely random. So just to make this point clear, let's say for some other parents, different mutation causes that skin to become blue in color. So mutations are random and that's important. Now let's see how this affects our population. You see the green colored beetles have an advantage. They are very hard to see. I'm pretty sure you can see that. So the crows also find them very hard to see, which means their chances of getting eaten is less. So they have a higher chance of survival compared to the red beetles and the blue beetles maybe. And therefore, more importantly, they have a higher chances of reproduction and making more copies of themselves. So as time passes, what do you think happens? See right now, the green beetles are minority. Most of the beetles are red in color. But as time passes, what do you think happens? Well, because green beetles have a higher chances of reproducing compared to their red colored cousins or blue colored cousins, we might expect their number to increase. And that's exactly what happens as time passes by. We will find that the red beetles start decreasing in number because they can be eaten very easily. They can be spotted very easily. But the green beetles cannot be spotted that easily and so they start increasing in number. Maybe the blue beetles also start getting eaten and before they have a chance of passing their DNA, maybe they get completely wiped out. That's totally possible because they were minority, had no advantage, and so they are completely gone. And after a few years or maybe many years, we might find that all the red beetles are gone and only the green beetles have survived. So let's think about what happened. Initially, the red colored beetles were more in number, which means the gene that is responsible for red color, that was more frequently seen in every generation. That was more frequently being passed on, right? So we can say initially or earlier, these genes, the genes responsible for red color had a higher frequency. That's the meaning of gene frequency. Gene frequency means which genes do you more frequently see in every generation, which gets more passed along. So that was ready initially to begin with because they were majority in number and the green and blue were very minority in number. But as years passed and this can take many, the amount of time it takes depends on a lot of stuff. It can take a few years or it can take a lot of years. It can take hundreds of years. So anyways, after many generations, what do we see now? We now see that it's the green colored beetles. They have become the majority, which means the genes responsible for green color, that is now more frequently seen. That is more frequently being passed along. So now the green colored genes, they have a higher frequency. In this population, the red colors are gone. They have become ancient. You don't even see them anymore. Any more only green color will be passed on. So this means, can we see that there has been a change in the gene frequency that we see? That's what we mean by change in the gene frequency, right? Earlier it was red, now it has become green. So there's a change in the gene frequency of the population of our beetles over generations, right? In other words, evolution has taken place. So this is evolution. From here to here, this is evolution. And so why did this happen? What caused this evolution? Well, two things. One, the mutation caused some changes in the traits. That's one thing, allowing different colored beetles to be formed. Second, one particular variant, the green colored one, had an advantage, meaning they had a higher chance of survival and a higher chance of reproduction because of which their numbers started increasing. And so this process in which the genes or the traits which have an advantage and because of which they can start being passed along more and more and start increasing in number, this process is what we call natural selection. And it's called so because this happened naturally. You see, the moment you have an advantage, naturally you will end up creating more copies of yourself but increasing in number. So what you're seeing over here is evolution by natural selection. Of course, there are other ways in which evolution can happen as well which we'll talk about in other videos. Anyways, natural selection is one of the major reasons why evolution happens. And this idea of natural selection was first proposed by a man called Charles Darwin. And because of his contribution, today we call him the father of evolutionary biology. Okay, now before you wind up, let's look at some of the important features of evolution. One important thing you can see is that evolution only makes sense over a population. It's wrong to say that an individual beetle evolved. That makes no sense. It's the population of the beetles that has evolved. Secondly, which is the most important point, I should think that in evolution, the nature forces you to change and adapt to the surrounding. Is that correct? Is the nature forcing these beetles to change? No! You see, the changes are happening randomly due to mutation. That has nothing to do with their environment. That would have happened regardless of what environment these beetles were in. Okay, so the changes happen randomly. But the nature helps in selecting which of those changes should get transferred, you know, should get passed along in the future generation and should increase in number. That's what natural selection is. So nature doesn't force you to change. Changes happen randomly, but nature helps you in selecting which one grows in number. Now, this might make you think, hey, the green variant is superior. The blue variant was useless. Again, that would be the wrong way to think about it. The green was superior only in this situation. But let me show you a different scenario. What if, as time passed on, even the bushes started changing its color? What if the bushes changed slowly to blue color? Now, I know this might sound ridiculous. I'm making this up, but I'm trying to say that, you know, environment can keep changing. And so think about it. What if the bushes had changed its color? Then the green wouldn't be selected and they would lose that advantage. They wouldn't have any advantage. And I'm pretty sure you would understand that it will be the blue that gets selected. And so now the beetles will evolve into blue color. So you see, all those random variations were important. These variations help prepare the species for our ever-changing environment. And so if you have lots of variations, you have lots of options for it to be selected and adapted to the environment. That's how evolution works. And so variations may not be very useful for individual organisms. Individual organisms might suffer because of the variation, but for the species as a whole, variations are super important. It's because of these random variations, natural selection can kick in and a species can adapt to various changes in environment. So that's pretty much it. Let's quickly see if we can go ahead and recall what we learned. So can you recall what is evolution? What is natural selection? Who is called the father of evolutionary biology? What causes variations? And finally, why variations are important for species? If you have troubles answering these questions, no worries. You can always go back and revisit the video.