For natural selection to cause evolution, it must select for or against one or more of the genotypes for a trait. In the simple case of a trait that is determined by a single gene with two alleles, there are five combinations of genotypes that nature can select:

1. either homozygote (AA or aa but not both)

2. both homozygotes (AA and aa)

3. either homozygote and the heterozygote (AA and Aa or aa and Aa)

4. the heterozygote (Aa)

5. all alleles (AA, Aa, and aa).

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

Which of the following is the most likely outcome of global warming

You see a white marker with an orange circle and black lettering. what does this marker tell you