Genetic Drift
Storyboard Text
- Yes, Harry, I agree, but I fear it may not last long. Do you see those dark clouds?
- It's a beautiful day, not a cloud in the sky, wouldn't you agree Sally?
- On a deserted beautiful beach, there is a population of birds. The gene pool is large and contains many different alleles. A gene pool is all the alleles of a population. The larger the gene pool the greater the genetic variation.
- A terrible hurricane makes landfall on the deserted beach before all of the birds can seek shelter and a few of the birds are caught up in the winds and swept offshore.
- When the winds finally quit, the birds who were swept out to sea, find themselves on a small island without any other birds and isolated from their beach friends. This is known as the founder effect and this small group of birds will now start their own population. Because there are only a few birds, the gene pool has been reduced, reducing the variety of alleles that their offspring can inherit.
- Because the gene pool has been reduced, the genetic variety has decreased, so all of the offspring will be similar in appearance.
- 20 years later . . . The once rare white feather allele is now the dominant form and makes up the entire population. The diversity of the groups has been reduced and now only consists of one feather color. The change in allele frequency over generations is a result of genetic drift. This new population drastically differs from the original group on the beach because of a chance event (hurricane) that caused the isolation of a few members of the original population.
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