SCN3230-ABED_1: Module 8 Lesson 3 - 3

Lesson 3 — Causes of Change in the Gene Pool

Impediments to gene flow often are geographical barriers. Provide three examples.

The bottleneck effect can occur after a natural disaster. Give three examples of natural disasters that could result in this type of genetic drift.

How can wildlife preserves prevent the negative effects of genetic drift and lost biodiversity in wildlife populations?

Which gene pool would most likely demonstrate micro-evolution?
1. A gene pool in Hardy Weinberg equilibrium
2. A gene pool bearing a new mutation
3. A large gene pool

Which matches a term correctly to its description?
1. gene flow - a chance change in allele frequencies when small populations become isolated
2. natural selection - a particular phenotype of mate is more often chosen
3. change in mutation rate - several new mutations arise in a short period of time
4. genetic drift - unrepresentative populations are separated from a larger population

Natural selection causes changes in allele frequencies, as does genetic drift. In natural selection, the environmental conditions cause increased survival of suitable genotypes versus unsuitable genotypes. In genetic drift, the allele frequency changes because the original population has been fragmented.

Mate selection refers to sexual selection where one phenotype may attract more mates, thus increasing the allele frequencies for the desired trait(s). This is similar to natural selection in that those with a given phenotype are being selected. In natural selection, the environment selects; in mate selection, the mate selects.

In heterozygote advantage, the heterozygote has a different phenotype than both homozygotes have, and it is this phenotype that is favoured.

Heterozygote advantage tends to keep allele frequencies even. An example is sickle cell anemia. SS results in normal red blood cells but susceptibility to malaria. ss results in sickled red blood cells but no malaria. The heterozygote (Ss) has relatively normal red blood cells and is protected from malaria.
Impediments to gene flow often are geographical barriers such as mountain ranges, canyons, oceans, and rivers. [You were asked for three.]
Examples of natural disasters that could result in genetic drift are rising or falling sea levels, avalanche, volcanic activity, and hurricanes. [You were asked for three.]
Wildlife preserves can prevent the negative effects of genetic drift and lost biodiversity in wildlife populations by arranging an artificial gene flow (immigration) in which individuals of the same species from distant populations are introduced to the preserve population.