Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why? a. increase (due to increased genetic drift) b. decrease (due to decreased gene flow) c. decrease (due to decreased mutation rate) d. decrease (due to decreased natural selection)

Video transcript

Hi everyone. Here's our next question in the event that all of the plants, pollen ears perish. Which of the following will decline, ultimately, ultimately resulting in decreased genetic diversity of the plant. Well, let's imagine here, our population of plants, you know, some flowers over here and the flowers over here and then far away in another field, another population of the same flowers over here. But they're different populations and maybe have some genetic differences between them. Well, when you had pollinators, you had genetic exchange between these two groups, the pollinators bringing genes from one group to the other, genes being exchanged between them. If the pollinators perish, you no longer have this gene flow exchange of values between one population and the other. That decreases or ends. Um And without that gene flow, you do decrease the genetic diversity of the plant because you don't have um the addition of aliens from both sets being exchanged between them, you just have them uh to isolated groups. So our correct answer choices. Choice C gene flow decreasing or ending as a result of pollinators no longer being able to exchange between these two groups. But let's just look through our other choice is to understand why they're not correct. Choice A Is the founder effect. The founder effect is when you have a small group isolated from its source population with a non representative, a little distribution. So a small group of people sails off to the new world and the uh an alley or represented in that group at a higher level because the small population, it occurs one in a million in the source population, but one person among 100 settlers has this alittle. So in the small isolated group that has split off from the main group, you have a non representative sample of the alleles in the source group. But that's not um what declines as a result of the death of pollinators. So you might have founder effect if there's one particular group of flowers, a very small group that's now isolated without pollinators. But we're saying overall what declines as a result of the pollinators dying. So founder effect is not correct to describe um what this question is asking for. So not our answer. Choice choice B says mutation. Um Well uh mutation is not going to decrease our as a result of the end of pollinators. These groups will keep on having gene mutation or whatever rate they did before. So that's not a correct answer. And finally, Choice D. Is stabilizing selection. Um That refers to when you have a distribution of phenotype sis. So perhaps something like this with some extreme phenotype on either end. Uh And selection favors the middle range of that phenotype. So you overall decrease the genetic diversity of the population because you're selecting against the extreme phenotype sis over time you're going to decrease genetic diversity. But we're not having a force of selection here. We're having these two groups being isolated from each other by gene flow decreasing between them. So stabilizing selection not the correct descriptor of what's happening here. So again, in the event that all of the plant pollinators perish which of the following will decline, ultimately resulting into decreased genetic diversity choice C gene flow. Thanks for watching. See you in the next video.