Descent With Modification

by Jason Amores Sumpter
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hi. In this video, we are going to talk about evolution. Yes, we have finally made it to the moment where we're going to scratch beneath the surface and get at what is evolution. So evolution, in the simplest sense, is just the change in of phenotype in a biological population over time, or just change over time in the simplest form. Now, evolution actually is a very old idea, and it kind of predates Charlie Darwin. So the first guy who's really credited with coming up with the theory of evolution was called Lamarque, and his ideas were referred to as Lamarque is, um, and this is that an organism passes on traits to its offspring that it acquired during its own lifetime. And he believed that whether an organism used or didn't use a particular body part, that would cause that body part to be strengthened or weakened, and this would affect some change in the organism's phenotype. So his example that he used was that of a giraffe, and he said that, you know, drafts there, you know, they started out. They didn't have these really long necks, so they kept stretching their neck. Thio, eat those leaves, and so over time they grew toe have longer and longer next, because they were strengthening that body part. They're stretching those necks out. During the course of one drops life, it would stretch its neck a little bit, causing it to grow a little longer, little stronger. And it would pass that on to its offspring, who would then stretch its neck a little bit during its life and so on and so forth until you get longneck drafts. We know today. Now, of course, that is not how evolution works. For one thing, use and disuse doesn't strengthen or weaken body parts like that. It doesn't work that way. Evolution is much better thought of as the way Darwin put it, this descent with modification. So Darwin's ideas about evolution are such that individuals in a population have different traits, right? They have different Khalil's for different things, so they have different traits and some of these traits. Some of these trait differences rather can be inherited, and every generation Onley, some individuals air going to survive until they can reproduce, and some will reproduce more than others and additionally, some individuals survive better and produce more offspring because of certain heritable traits or traits that can be inherited. So basically, if we look at this giraffe example, what Darwin would say is all right, so early on you have some drafts with shorter next, Like we see here, you got drafts with longer necks and, well, those drafts with shorter necks. But they're going to die. They're going to die out because they are not going to survive as long or produces much offspring as the drafts with the longer necks. So those drafts with longer necks are going to be more successful in over time. They're going to become the most prevalent member of their population, and these short neck drafts they're gonna keep dying off. And Darwin called this process this process by which heritable traits become mawr or less common in a population because of differences in reproductive success between the individuals who have those traits. He called this idea natural selection. So essentially the drafts with long next we're naturally selected and became mawr common in the population. That trait of longneck became more common because it allow the drafts to get more food, which would allow them to survive better, which would allow them to produce more offspring. So this day differs very much so from remarks idea, right? These changes are not as direct. They're not as immediate. The whole process is a lot more passive in a sense. Now let's turn the page and talk about some more specifics about evolution.