evolution exam 2

What is evolution?

Change in allele frequencies in a population over time

What are the three causes of evolution?

Natural selection, gene × environment interaction, genetic drift

What is genetic drift?

Random change in allele frequencies due to chance

Is genetic drift biased?

No, it is random

When is drift strongest?

In small populations

What does drift do to variation?

Reduces it

What happens to heterozygosity under drift?

Decreases

What is allele fixation?

Allele frequency reaches 100%

What is allele loss?

Allele frequency drops to 0%

What is gene flow?

Movement of alleles between populations

What is coalescence?

Tracing alleles back to a common ancestor

What is a deme?

Local breeding population

What is effective population size (Ne)?

Number of individuals contributing genes to next generation

How does small Ne affect drift?

Increases drift

What is a bottleneck?

Sudden population reduction

What is the founder effect?

New population started by few individuals

Effect of both on variation?

Reduced genetic diversity

What is a molecular clock?

Mutation rate used to estimate divergence time

Which evolves faster: mitochondrial or nuclear DNA?

Mitochondrial

What is Kimura’s neutral theory?

Most mutations are neutral and evolve via drift

Are most nonsynonymous mutations beneficial?

No, usually harmful or neutral

What is positive selection?

Favors beneficial mutations

What is purifying selection?

Removes harmful mutations

Stabilizing selection?

Favors intermediate traits

Directional selection?

Favors one extreme

Disruptive selection?

Favors both extremes

What defines an adaptation?

Heritable trait that increases fitness and evolved by selection

What is an exaptation?

Trait repurposed for a new function

What is convergent evolution?

Independent evolution of similar traits

Cause of convergent evolution?

Similar environments

What is a cline?

Gradual change in traits across geography

Why is gene duplication important?

Allows new gene functions

What is Batesian mimicry?

Harmless species mimics harmful one

What is the comparative method?

Compare species to study adaptation

What must it control for?

Shared ancestry

Difference between sex and reproduction?

Sex = gene exchange; reproduction = producing offspring

Is conjugation reproduction?

No, it is sex only

What is horizontal gene transfer?

DNA transfer between organisms

What is the twofold cost of sex?

Only females produce offspring

Benefit of sex?

Increases variation

What is Muller’s ratchet?

Accumulation of harmful mutations in asexual populations

What is anisogamy?

Different gamete sizes

Why are eggs costly?

Large and resource-heavy

Why are sperm cheap?

Small and numerous

What is kin selection?

Helping relatives to increase shared genes

When is prosocial behavior strongest?

High relatedness

Direct benefits model?

Mate provides resources

Good genes model?

Mate has high fitness

Fisherian runaway?

Trait + preference reinforce each other

Sensory bias?

Preference exists before trait

Overt competition?

Physical fighting

Covert competition?

Sperm competition

What is cuckoldry?

Raising another male’s offspring

What is sexual conflict?

Male and female evolutionary interests differ