Chapter 16: How Populations Evolve

Flashcards covering key concepts from Chapter 16 on how populations evolve.

What is a population?

A group of organisms of the same species living in the same geographic area.

What evolves — individuals or populations?

Populations evolve, not individuals.

What is evolution in genetic terms?

A change in allele frequencies in a population over time.

What is microevolution?

Evolutionary change within a population.

What is population genetics?

The study of genetic diversity and how allele frequencies change over generations.

What is a gene pool?

All the alleles of all genes in all individuals in a population.

What is allele frequency?

The percentage or proportion of a particular allele in a population.

What does p + q = 1 represent?

The allele frequencies of two alleles in a population.

What does Hardy-Weinberg equilibrium represent?

A stable, nonevolving population where allele frequencies do not change.

What is the Hardy-Weinberg equation?

p² + 2pq + q² = 1.

What do p², 2pq, and q² represent?

p² = homozygous dominant, 2pq = heterozygous, q² = homozygous recessive.

What are the 5 conditions of Hardy-Weinberg equilibrium?

No mutation, no migration, large population, random mating, no selection.

What happens if any HW condition is violated?

Evolution (microevolution) occurs.

What is mutation?

A change in DNA sequence that creates new genetic variation.

How common are mutations?

About 1 in every 100,000 cell divisions.

How do mutations contribute to evolution?

They introduce new alleles into the gene pool.

What is gene flow?

Movement of alleles between populations through migration.

What factors influence gene flow?

Distance, ability to move, and species behavior.

What is genetic drift?

Random changes in allele frequencies due to chance events.

Why does genetic drift affect small populations more?

Chance events remove a larger percentage of individuals from small gene pools.

What is the bottleneck effect?

A severe reduction in population size leading to loss of genetic diversity.

What is an example of the bottleneck effect?

1992 Florida panthers reduced to 20–30 individuals.

What is the founder effect?

When a few individuals form a new population with reduced genetic variation.

What is inbreeding?

Mating between relatives; increases expression of recessive disorders.

Does inbreeding change allele frequencies?

No — but it changes genotype frequencies.

What is nonrandom mating?

Choosing mates based on traits; affects genotype distribution.

What is assortative mating?

Choosing a mate with a preferred phenotype.

What is natural selection?

A process that favors individuals with traits that improve fitness.

What are the three types of natural selection?

Stabilizing, directional, and disruptive selection.

What is stabilizing selection?

Selection for the intermediate phenotype (e.g., human birth weight).

What is directional selection?

Selection for one extreme phenotype (e.g., antibiotic resistance).

What is disruptive selection?

Selection for two extreme phenotypes over the intermediate.

What is sexual selection?

Selection for traits that increase mating success.

Why are females choosy in sexual selection?

They produce fewer eggs, so mate choice is more important.

What is the good genes hypothesis?

Females choose males with traits that improve offspring survival.

What is the runaway hypothesis?

Females choose males for exaggerated traits related to appearance.

What is sexual dimorphism?

Differences between males and females, often due to sexual selection.

What is male competition?

Males competing with each other for access to females.

What is a harem?

A group of females defended by one dominant male.

What are sneaker males?

Males who reproduce by avoiding detection from the dominant male.

What is territoriality?

Defending an area against rivals.

How is diversity maintained in a population?

Through mutations, sexual reproduction, and genetic drift.

Why is natural selection imperfect?

Evolution works with existing variation and involves trade-offs.

How does the environment maintain diversity?

Different conditions favor different phenotypes, allowing polymorphism.

How can environmental change promote speciation?

By maintaining different traits in different subpopulations.