lecture 20: microevolution

What is evolution?

Decent with modifications

What drives evolution?

Natural selection

natural selection

Nature selecting the most fit individuals

gene pool

total collection of alleles in a population (all versions of genes in a population)

allele frequency

Percentage of all loci for a particular gene

gene flow

Exchange of alleles between neighboring populations

-random sampling influences allele frequencies

-does not cause adaptation

genetic drift

Changes to the gene pool by random chance

-bottleneck effect

-founder effect

What is a bottleneck?

Drastic reduction in population size

-random alleles overrepresented (drastically alters gene pool)

-reduces population variability

How does it reduce population variability?

Random survival of certain alleles

What is the founder effect?

Isolated populations reflect traits of the founders

How does gene flow increase genetic diversity?

By spreading alleles from different environments

What are the outcomes of natural selection?

-directional

- disruptive

- stabilizing

Directional

Population shifts to one particular direction due to change in the environment

Disruptive

when the population is split, commonly occurs in diverse or patchy environments

Stabilizing

Homogenize population (population drives towards a middle ground) occurs on many generations of a stable environment

What is sexual selection?

More attractive mates have greater reproductive success

Describe an example of sexual selection.

-sexual dimorphism

-competing for mate