Evolution can Occur Via Natural Selection

by Jason Amores Sumpter
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So now that we've discussed adaptation, fitness and natural selection in this video, we're going to define evolution and talk about how one of the ways that evolution can occur is via natural selection. And so most people have some preconceived idea of what evolution is through watching fictional sci fi TV shows and cartoons and things like that. And so maybe you guys think an example of evolution would be a pair of wings popping out of my back and me floating away like a little butterfly. However, that is not what evolution is about at all. Evolution does not have anything to do with physical changes. Instead, scientists define evolution in a very specific way, and so evolution is defined by scientists as changes in the D N A. Of a population over multiple generations or over long periods of time. And so really, evolution just means changes in the DNA of a population. And so again, changes in the DNA of a population may or may not result in physical changes. And so this is how you should know evolution is defined now. Evolution can occur in a wide variety of different ways. But what you guys should know is that one of the ways that evolution can occur is via natural selection, which we already discussed in our last lesson. Video now evolution. The changes in DNA of a population over long periods of time has shaped all life on Earth. And really, evolution is what is responsible for life's incredible diversity and so down below. In our example right here, we're going to look at an example of evolution by natural selection. And really, this image that we see right here is an example of natural selection. And it's very similar in many ways to the natural selection image that we showed with giraffes in our previous lesson video. And so they're both showing classic examples of natural selection. But here we're specifically showing natural selection in the context of evolution. And so what I want you guys to notice is down below. In our image, we have this population here of beetles and notice that within this population of beetles, we have some genetic diversity. We have these green or dark beetles, and then we also have these orangish light colored beetles. And another thing for you to notice is that the background or The natural environment that these beetles are in is pretty light colored. It's a tan color. And so, uh, one thing toe. Also note is that most of the Beatles in this population are dark Beatles, their dark greenish beetles that you see here. And so that's something important to note here. Now. Notice also that we have these birds here, and the birds are feeding on these on this population of beetles. However, because the natural background the natural environment is light colored, these birds can see the dark beetles so much easier than they can see the light colored orangish beetles. And so because they can see the dark colored beetles a lot easier, these birds are just going thio eat the dark colored Beatles mawr often than they eat the light colored beetles. And so generations later, if this selective pressure of the birds eating the dark Beatles continues toe happen over long periods of time. Ultimately, what we'll have is an evolving population of beetles. Notice that their arm or orange Beatles showing up over time because these orange beetles have a lot, uh, a higher likelihood of surviving and reproducing since they blend into their natural background. Ah, lot better than the dark beetles do. And so the reason that this is an evolving population of beetles is because noticed that the DNA of the population is starting to change over long periods of time. Generations later here we have mostly dark beetles, and over here this population is starting to evolve because the DNA in the population is starting to change to these orange colored, uh, beetles, the DNA in the orange colored beetles. And so if these birds continue Thio, eat all of these dark Beatles, uh, generations later, over long, long, long periods of time, Eventually all of the dark beetles will be gone. And on Lee, the orange beetles will remain. And again, the orange Beatles air here because they blend in to their environment better and they're therefore able to survive and reproduce better. And so what we have now over here on this side is mostly the light or the orange colored beetles. And so what we can see is that we've gone from mostly dark Beatles, uh, in the population of beetles to mostly light Beatles over here over time. And so this here because we have a change in the DNA of the population over multiple generations. DNA that allows for dark beetles mostly, uh, changing thio DNA for light Beatles within the population. This is a classic example of evolution, but by natural selection. And so this year concludes our lesson on evolution and how it can occur via natural selection, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you guys in our next video.