Question

to include a decrease at high densities as well.) aw a graph of per capita growth rate versus N illustrating this concept. (Be sure frequendeesens evolve as a result ofcout how genetic drift works, acco So far you have learned the basis ahh e tic drift works, according to the idea that populations evolve as a result of m o r. Now consider this prediction: Allele Trequencies change by genetic drift equally quickly in large populations and small populations. A. Do you agree with this prediction? us. Describe a study that would test the prediction. Include a description of the results you would expect to see if the prediction is correct. (7) Inbreeding can quickly remove deleterious recessive alleles from a population. Imagine a population with two alleles for a gene, rand R, where homozygotes with genotype ir die before reaching sexual maturity. Discuss why r would be purged from this population faster if Individuals engaged in Inbreeding versus if they do not. (8) The Invasive cane toad was introduced to Australia in the 1930s. The toads are extremely poisonous to red-bellied black snakes, and there was some concern that the snake population might be decimated. However, the snakes and toads seem to be co-existing. Small-headed snakes are less able to eat the large toads and are thus less likely to be poisoned. Imagine a biologist surveyed red-bellied black snakes in areas with and without cane toads, and her results are depicted in the hypothetical graph below. The data in the graph suggests that smaller snake heads are favored by natural selection in the presence of cane toads. Explain what three assertions must be true about the red-bellied black snake population in order for natural selection to be occurring. Mean snake head size (cm) w Cane toads absent Cane toads present 18) The boll weevil is an insect native to Mexico and Central America and is a pest of commercial cotton. When chemical insecticides were first discovered, they proved highly effective in controlling boll weevil outbreaks. Within a few decades, however, many boll weevil populations were resistant. Explain how the boll weevil populations changed.

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question 6-8

Answer 1

Ques 6) A) No, this prediction is false. (explanation is given with example in B part of this question.)

B) Example: Introduction of Japanese bush warbelers (bird species) in Hawaii. Since they were a small population genetic drift was observed in this species when they were introduced in hawaii in 1990s. Conditions like climate change, and Avian malaria affected these birds in a chance format since they lived in different islands. Hence, resulting in genetic drift.

genetic drift affects smaller populations more because of the simple fact that the number of Individuals are less and therefore their chance of getting affected is higher whereas in a bigger population more number of individuals are present hence the chance of irradicating a particular combination of alleles is lower just because the number of individuals with that combination of alleles is higher.

Ques 7) Inbreeding occurs when individuals consisting of similar genetic makeup decide to mate. The consequences of inbreeding include smaller gene pools which result in a higher chance of concieving a genetic disorder in a progeny. for example: If r and R mate their progenies will be rR, rR, rR, and rR. And if these progenies mate amongst themselves the resultant will be rr, RR, rR, rR i.e. 1:2:1 genetic ratio. Therefore, resulting in a higher chance of getting rr in the progeny. If there was a bigger gene pool and more variants of the same allele the chance of getting rr would be reduced.

rr would get purged simply because the gene pool is small and the chance of some varition in the allele is lower due to the limited gene pool. And since rr results in a genetic disorder where the progeny dies before reaching sexual maturity, the next genetion for rr is impossible. Therefore, they'll be purged from this population faster than all the other allelic combinations.

Ques 8) 3 assertions are listed below:

i) Genetic variation: The difference in the genetic makeup is resulting in smaller or bigger heads. Therefore this variation is supporting the small headed snakes.

ii) Genetic Drift: Introduction of toads result in genetic drift in the snake population. The chance advantage of having a small head in snakes is resulting in the elimination of bigger headed snakes due the the presence of poisonous toads.

iii) Selection Pressures: External biological factor which is the introduction of this new poisonous prey results in putting selection pressure on the snake population and the smaller headed snakes are at an advantage.