Question

A population of 150 fish have two alleles for the size of a black spot on their sides: large spot alleles and small spot alleles. The large spot allele is dominant.
For each situation listed below, identify the mechanism of evolution at work. Select whether it is an example of natural selection, genetic drift, or gene flow.

1. A fish net captures twenty fish, all who happened to have large spots.
2. Small spotted fish escape from predators better.
3. 15 large spotted fish move into this population.
4. Fish-eating birds catch large spotted fish more easily

Options:
A. Gene flow
B. Genetic Drift
C. Natural Selection

Answer 1

Answer:

1. genetic drift; 2. natural selection; 3. gene flow; 4. natural selection

Explanation:

1. A fish net captures twenty fish, all who happened to have large spots:

The mechanism of evolution that is playing out in this situation is most likely genetic drift. Genetic drift occurs  when a random change occurs, resulting in the selection of a number of individuals by chance, rather than based on their level of fitness. The fish with large spots allele were selected against by chance, not necessarily because the fish with the small spot alleles were better fitted.

2. Small spotted fish escape from predators better:

The situation here is natural selection. The small spotted fish possess a greater fitness as they become well adapted to escaping from predators better than the large spotted fish, which gives confers on them a greater fitness to be selected for against the large spotted fish.

3. 15 large spotted fish move into this population:

The movement or introduction of new individuals i nto a population is what is referred to as gene flow in evolution, which is another mechanism of evolution that changes the allele frequency of the original population.

4. Fish-eating birds catch large spotted fish more easily:

This is another example of natural selection. The small spotted fish possess a greater fitness which makes them not easily preyed upon by Fish-eating bird easily, compared to large spotted fish. Natural selection favors the fish with small spotted alleles against the large spotted fish, and as a result, more small spotted fish would survive and reproduce more offspring with the small spotted alleles compared to those with large spotted alleles.