9.4 genetic drift & 9.5 migration

Define genetic drift

The random, non directional change in allele frequency between generations occuring by chance

In what population is genetic drift particularly significant in

Small populations

explain the founder effect

an example of genetic drift;

• When a small group moves away from its homeland

  causing small groups in new population to;

• Have a different allele frequency from the original population

• Decreased genetic variation

Explain the bottleneck effect

When the population size is dramatically reduced, the allele frequency, chance, may be different from the original population

Define species

A group of individuals that share many characteristics and are able to interbreed under natural conditions to produce fertile offspring

Define speciation

a process by which populations evolve to become different species

what are the steps to speciation

1. Variation: there is variation between individuals of a species

2. Isolation: populations are isolated without gene flow

3. Selection: each population is subjected to different selective agents

4. Speciation: appele frequencies change so much that interbreeding is no longer possible