Question

RED EXTRA CREDIT EXERCISE: INTERACTION BETWEEN EVOLUTIONARY FORCES A species of mice inhabits a coastal plain of white sand (See Fig. 1). The most common fur color ispale gray, making up 85% of the population. The dominant allele for coat color is black, with the recessive allele coding for the pale gray phenotype. The mice mainly feed on seeds from the local Moave grass, but a few (10%) are also able to digest the young growing shoots of the local Splunka bush, because of a specific dominant allele at a separate locus to coat color. All mice have some ability to climlb Propose a scientific reason for the gray color being the more common phenotype in this population colan can ne rce ricane hits the beach. By chance, th uction in population resulted in all the mice on the mainland that could eat the Mainland Splunka bush dying. What is the name of the evolutionary force that is in operation at this point? 气 A small population of mice was also washed out to sea on driftwood, and lands on a nearby volcanic island. The population contains mice of each phenotype, but the allele frequencies are now different to the original population. What is the name of the evolutionary force at work here? The volcanic island (see Fig. 1) is covered in a fertile black soil which allows the Splunka bush to grow more abundantly than the Moave grass, although both types of plant are found all over the island. Multiple genes and respective alleles affect height in the Splunka plant. The Island Splunka bush is much taller than the Splunka bush on the mainland: essentially, it becomes a tree on this island. Those mice that can eat the Splunka shoots must climb up the stems to reach the shoots Gray sand is limited to one extreme edge of the island. The mice that land on the island begin to feed and breed and migrate across the island. Describe the microevolutionary forces that will now be at work on the mouse population on the sland. The winds from the hurricane also carried pollen containing several alleles encoding for tall height from the Island Splunka tree over to the mainland where it pollinated flowers on the Mainland Splunka bush. Name the evolutionary force at work here. Over several generations, what will happen to the Mainland Splunka bush?

Answer 1

1. The grey mice are camouflaged by the grey sand on the ground. They will be less noticable to the predators an this provides then more chances of survival. Thus, grey coat color has been selected by nature over the black one. The black mice are predated upon and have less chances of survival and reproduction.

2. Genetic drift is in play.

3. This has resulted in gene flow.

4. The grey coat color mice will migrate to the grey sandy corner of the island. The microevolutionary force active here is migration. Since the splunka bush is present predominantly in the black area, and they are taller, the mice which are black in color and can climb and who feed on the splunka bush will now predominate in this region and will get selected. Hence, natural selection comes into play at this point.
The mice which are grey in color, and feed on moave grass will predominate the sandy edge of the island.

5. Gene flow is active here. The splunka bushes in the mainland would soon grow into trees like those on island.

6. The allele frequency of the black coat mice which feed on the splunka bush and can climb well will increase in the volcanic ash black area of the island. The sandy edge will consist predominantly of grey coat mice which feed on moave bush and have little ability to climb. Thus, genotype frequency of these mice will increase in this area and decrease in the volcanic area.

7. The evolutionary force at work is genetic drift and natural selection. A random event such as volcanic activity wipes of the population on the ground without any bias. Those mice which had good climbing skills could climb the canopies and be safe now predominate the island, thus changing the gene frequencies. Thus, they were selected as opposed to the others for survival and reproduction.