There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from a. genetic drift. b. gene flow. c.nonrandom mating. d. directional selection.

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Welcome back. Our next problem says suppose a plant has two different alleles for flower color, one red big R. And one white little R. In a population of 10 plants. The frequency of Big R. And little R. Is 0.5 each. However only six of these plants produce viable offspring by chance, resulting in a shift of the frequencies of Big R. 0.8 and little R. 0.2 in the next generation identify the cause of such a shift. So we have a situation where we have a first generation In which 50% of the population Has the big are alive and 50% as the little are alive. Now only six individuals reproduce and have viable offspring. So in the second generation we now have a different situation where instead of half and half we have 80% of that second generation having Big R. And only 20% having little are. Now what's really important to notice is that the problem tells us this occurred by chance. So there wasn't any sort of environmental factor or anything else that meant that only those six were more likely to reproduce. Those six had a better chance. Um It just happened that that's what occurred. So that's really key here. There's no advantage evolutionarily to one alley over the other. So this is telling us what is the cause of this happening. So let's look at our choices. Choice A. Is genetic mutation. Well genetic mutation is a change to the D. N. A. In this case we don't have any change your DNA. We still have the same exact values for the red and white flower colors. So that does not describe our situation here. So we can eliminate choice A. Choice B. Is genetic recombination. Well, recombination occurs as we recall in reproduction and it involves two chromosomes meeting up having a crossover event exchanging some some portion of their chromosome. So again it involves a change to the D. N. A. Which does not describe what's happening here. So Choice B. Is not correct. Choice C. Is genetic drift. While genetic drift does describe exactly our situation here. It's when you have a change to the frequency uh valuables and that changes due to random chance. So that's exactly what we have happening here and therefore correct answer is C genetic drift is what describes this shift. Finally, we'll just look at choice. The genetic variation that just describes when you have multiple alleles of the gene in the population um which we do have here. That's true. But that's not the cause of the change that occurred between generations. So Choice D. Is not correct. So the correct answer is c genetic drift. Thanks for watching See you in the next video

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Key Concepts

Genetic Drift

Gene Flow

Nonrandom Mating