Question

ANT 120

Lab 1: The Forces of Evolution

There are four mechanisms that can lead to evolutionary change from one generation to the next: mutation, natural selection, gene flow, and genetic drift. In this laboratory exercise we will examine the action of genetic drift and natural selection. The key difference between these two mechanisms, which can be difficult to get a handle on without direct experimentation, is that natural selection privileges some individuals over others on the basis of their biological traits while genetic drift privileges some individuals over others with no regard to their biological traits.

Data Table for Genetic Drift Experiment

	Frequency of black beetles (alleles)
Generation	0	1	2	3	4	5	6	7	8	9	10
Round 1	0.5	0.5	0.6	0.6	0.5	0.4	0.6	0.8	0.9	0.8	0.7
Round 2	0.5	0.4	0.4	0.5	0.3	0.2	0.2	0.3	0.1	0.0	0.0

Data Table for Natural Selection Experiment

	Frequency of black beetles (alleles)
Generation	0	1	2	3	4	5	6	7	8	9	10
Green Forest	0.5	0.5	0.5	0.4	0.2	0.2	0.3	0.3	0.2	0.1	0.0
Black dirt	0.5	0.6	0.6	0.7	0.8	10.0	10.0	10.0	10.0	10.0	10.0

After tabulating your data, answer the questions on the other side of this sheet.

Questions

Compare the results from the genetic drift experiments to the natural selection experiments. Are there any clear differences in the results? If so, what is the reason for the differences?

In cases where one of the colors of beetle was eliminated, how could the allele for this color re-enter the population? Which forces of evolution would be required?

From these experiments, how might genetic drift and natural selection affect natural populations of organisms differently? If the population of beetles was 20,000 instead of 20 (and 10,000 survived each generation) how would this influence the effects of genetic drift vs. natural selection?

Is the outcome of genetic drift or natural selection more predictable? How might these different mechanisms of evolutionary change relate to functional traits of organisms?

Answer 1

On making a comparison between both the experiments of genetic drift and natural selection, there is a pattern found in the way selection is made. In case of genetic drift it is observed that round 1 is being constant with slight change in the frequency but when it comes to round 2, it is gradually getting diminished which means frequency by the 9^th and 10^th generation is also nil. It shows that it is time that is bringing the gradual changes. In case of the natural selection process, it is observed that the black dirt is being more favoured for the allele as compared to green forest and the bettles on black have more frequency of the allele.

Random events can bring back the allele or re-enter the allele into the population. If the beetles start to mate randomly with a beetle that has the allele of that particular colour, it can re-enter the population.

The genetic drift and natural selection affect natural population because there are changes and mutations made depending on the traits. In case of the natural selection, the ones with superior traits are able to survive and go to the next generation. Hence, it affects the natural population as it favours only superior and certain biological traits. Genetic drift is based on particular trait but it can affect natural population due to its extensive mutation and changes through evolution.