Chapter 16: Genes & Evolution Flashcards
(25 cards)
What is evolution in a population?
Change in allele frequencies over time.
5 conditions for Hardy-Weinberg equilibrium?
No mutation, no migration, large pop, random mating, no selection.
What does Hardy-Weinberg predict?
Genotype frequencies in non-evolving populations.
4 agents of evolutionary change?
Mutation, gene flow, genetic drift, natural selection.
Types of natural selection?
Stabilizing, directional, disruptive.
What is stabilizing selection?
Favors average traits.
What is directional selection?
Favors one extreme trait.
What is disruptive selection?
Favors both extremes, not average.
What is sexual selection?
Traits picked for mating success.
What is heterozygote advantage?
Heterozygotes have higher fitness.
What is Hardy-Weinberg equilibrium?
When allele frequencies stay constant in a population
Requires no evolution happening. Ex: A large, isolated population with random mating and no mutation.
What is gene flow?
Movement of alleles between populations
Ex: Migration of individuals between two islands.
What is genetic drift?
Random change in allele frequencies
Stronger in small populations. Ex: Bottleneck or founder effect.
What is the bottleneck effect?
Population size drops suddenly
Genetic diversity decreases. Ex: Natural disaster wipes out most of a population.
What is the founder effect?
New population from a few individuals
Alleles may be very different from original group. Ex: Small group colonizing an island.
What is assortative mating?
Mating with individuals that are similar
Ex: Tall people pairing with tall people.
What is stabilizing selection?
Favors average traits
Ex: Human birth weight—not too small or too big.
What is directional selection?
Favors one extreme trait
Ex: Antibiotic resistance in bacteria.
What is disruptive selection?
Favors both extremes, not average
Ex: Light and dark mice survive, but not medium.
What is heterozygote advantage?
Heterozygotes have higher fitness
Ex: Sickle cell carriers resist malaria.
What is sexual selection?
Traits increase mating chances
Ex: Peacocks with bright tails.
What is fitness?
Ability to survive and reproduce
Ex: More offspring = higher fitness.
What is sexual dimorphism?
Differences between males and females
Ex: Male lions have manes, females don’t.
What is dominance hierarchy?
Ranking order in social groups
Ex: Alpha wolves lead the pack.
