Lecture 5 - Mechanisms of Evolution Flashcards
What are the 4 mechanisms of evolution?
- Mutation
- Gene flow
- Natural Selection
- Genetic Drift
What is gene flow?
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
Why is natural selection a type of adaptive evolution?
It increases the frequency of traits that enhance survival or reproduction over time. It is the only mechanism of evolution that consistently leads to adaptive evolution.
Why is natural selection the major mechanism of evolution?
Mutations and gene flow have a lower impact and usually lead to natural selection.
What is relative fitness?
It is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
What are the 3 modes of natural selection?
- Directional selection
- Stabilizing selection
- Disruptive selection
What generally causes stabilizing selection?
Predation
What is the general effect of disruptive selection?
Speciation
What are 4 constraints on natural selection?
- It can only act on existing variants
- Evolution is limited by historical constraints
- Adaptations are often compromises
- It interacts with chance and the environment
What is genetic drift?
It is a change in allele frequencies due to chance, so it can cause random changes that aren’t adaptive or can cause alleles to become fixed. It occurs in all populations but has a larger effect on small populations.
What are the two types of genetic drift?
The bottleneck and founder effect.
What is INTRAsexual selection?
It is selection within a sex to compete for mates.
What is INTERsexual selection?
It is selection by one sex for mates aka mate choice.
