Grade 11 Biology – Evolution Investigation

SBI3U1-03
Lucas DaSilva
For: Mr. Toffoli
Due: 3/3/2015

Purpose

The purpose of this lab was to investigate the phenomenon of genetic drift and its significance to allele variation.

Materials

25 red chips
25 white chips
Paper bag

Procedure

In Part A, students were first required to calculate the allele frequencies for the original population by counting the number of both white and red chips. Next, the first, second, third, and fourth waves of migrants’ allele frequencies were calculated by randomly drawing ten individuals from the population of 25. Results were recorded on the observations table followed by repeating of the process. Finally, allele frequency averages were calculated and recorded in the observations table. In Part B, alleles from the fourth generation of migrants were placed back into the bag. Next, four alleles (two individuals) were removed from the bag to represent the alleles of parents. The alleles would then be randomly combined from each parent to produce two offspring. These results were recorded in the observations table, and this process was to be repeated another two times. Finally, calculations of allele frequencies of the population consisting of the six offspring were completed and compared with both the fourth migrant population and the original population.
Observations and Calculations Chart
PART A:
Number of Red
Number of White
Gene Pool Size
Red Allele Frequency
White Allele Frequency
Original Population
25
25
50
0.5
0.5
1st Migrant
7
13
20
0.35
0.65
2nd Migrant
13
7
20
0.65
0.35
3rd Migrant
13
7
20
0.65
0.35
4th Migrant
9
11
20
0.45
0.55
Average
10.5
9.5
20
0.525
0.475

PART B:
Male
Female
Offspring A
Offspring B
RR
RW
RW
RW
RW
WW
WW
RW
RW
RW
WW
RW

Frequency of Red
0.33
Frequency of White
0.67

Questions for Conclusion

1. The phenomenon demonstrated in this investigation is genetic drift. Genetic drift is the change in distribution of alleles due to chance events in a breeding population. This is important in all organisms because through this process, more diversity can be achieved in a species. Genetic drift can be demonstrated by the example of rolling two dice to see which numbers you land on (a game of chance). The numbers that occur cannot be foretold definitely, and therefore are completely random. This process is what results in a higher diversity, essentially driving evolution.

2. The first opportunity in which there could be a change in allele frequency occurs in Part A where four waves of migrants were pulled out of a gene pool consisting of 50 alleles in which half were red (25) and the other half white (25). Observed through the four waves of migrants, the number of red and white alleles varied drastically, demonstrating the randomness of the process of genetic drift, therefore altering the chances of which parents will receive which kinds of alleles due to quantities in the gene pool. The second opportunity where changes in allele frequency could have occurred is in Part B,