Biological Species

by Jason Amores Sumpter
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hi. In this video, we're going to talk about species, what they are and how they form. Now. Speciation is the process by which an ancestral species splits into two or more species, and we can see that there are really two types of evolution at play or to kind of broad categories. You can have micro evolution, which is the change in alil frequencies in a population and macro evolution, which is broad patterns and evolution well above the species level. So speciation kind of serves as a link between micro and macro evolution. As the change in Lille frequencies in a population grow, we can eventually have a speciation event, which ultimately will lead thio patterns of broad evolution over long periods of time. Now we're normally going to be talking about species according to the biological species concept, which is basically the idea that species are defined by reproductive barriers. So what does this mean? Well, you can have something called reproductive isolation, which are basically mechanisms that prevent two species from mating and producing viable offspring, and we'll get into the details of that in just a moment. However, it's also worth noting that you can also form hybrids which are offspring that result from inter species mating. However, thes offspring tend to not be viable, and we'll talk about what all that means in a moment. So here you can see a sort of nice example of speciation. You have this initial population of fruit flies, you separate them and give them different foods and let them, uh, go through several several generations of breeding. And then when you mix those two populations back together, well, most of the yellow flies that were in this had the starch available is food. They're gonna want to mate with each other. Those maltose flies, they're gonna want to stick with each other. Inmate You might have a few that will mate with each other, but you have the beginnings of speciation. These organisms are starting to diverge. Now, when we talk about reproductive isolation, there are different types of barriers that must be overcome. And we group these into pre psychotic barriers as in mechanisms that prevent zygote formation and post psychotic barriers which prevent thes I go from functioning properly. So pre psychotic barriers include gametes that won't fuse behavioral differences in court, in courtship and what's called mechanical isolation, which is basically the idea that organisms don't have the right parts to mate. Uh, think of this as a sort of round hole square peg scenario. Now, post psychotic barriers are basically when hybrids are sterile or do not survive. They die very quickly because again, these are not viable offspring. So if the offspring are sterile or, uh, do not survive and die very quickly, that means they are not viable. And over here you see a nice example of post psychotic barriers. These organisms are called Lie Gers. Yes, this is a hybrid between a lion and a tiger. It's Napoleon Dynamite's favorite animal. And guess what? Lie gers are totally sterile. You can make laggers, but you can't have laggers mate with each other and make more laggers. You can Onley form the hybrid through a mating of a lion and a tiger. Now let's turn the page and talk about some other details