22. Evolution of Populations
Genetic Drift
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In our example, we have western snowy plovers that are shorebirds that live along the American West Coast. Now after a flood, a particular population of west east western snowy plovers went from 437 down to just 26 there. Now Western snowy plovers are known for having large black spots on their faces, but the population that survived the flood happen to have relatively small facial spots. Assuming that face spot size is a heritable trait, answer the following questions. Alright. A says, what if what changes, if any, do you expect in the offspring of Western Snowy Plovers that survived compared to the original population? Alright. So what do you think? Alright. This one's pretty straightforward, right? We said we have a trait that can be inherited facial spots and the ones that survived have smaller facial spots. So I'm gonna say here that I would expect next generations, future generations to have smaller facial spots. Not smaller than the ones that survived, but smaller than the original population because those are the individuals that survived. Okay. So that leads us to b. It says, what special case of genetic drift describes this scenario? Alright. So what do you think? Well, this sounds like to me a population population bottleneck. Right. When a population sort of crashes at some point, usually due to some environmental cause, and you know, that is going to eliminate a lot of genetic variation and a lot of it randomly. Alright. Now our final question here, c, what are two ways genetic diversity could be increased in this population in the future? Alright. So how could we get genetic variation back into this population? Well, one way probably could be mutation. Right? Mutation could increase new alleles, and that would increase genetic variation again over time. And another way though, well, we might say gene flow. Alright. Gene flow brings alleles in from other populations. So if another population of this western snowy plover didn't go through this population bottleneck or, you know, maybe it did, but other alleles were were, preserved in the population, if there's gene flow between populations, you could restore some of that genetic variation. Alright. More practice after this. Give it a try.
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