AP Biology Ch. 23 The Evolution of Populations

What is microevolution?

Changes in the allele frequencies in a population over generations.

What is a population in evolutionary biology?

A group of individuals of the same species living in the same area that interbreed and share a gene pool.

What is a gene pool?

The total collection of all alleles for all genes in a population.

What is allele frequency?

The proportion of a specific allele among all alleles for a gene in a population.

What does it mean for evolution to occur in a population?

Allele frequencies change from one generation to the next.

What is the Hardy-Weinberg principle?

A model stating that allele and genotype frequencies remain constant from generation to generation if no evolutionary forces act on the population.

What is the Hardy-Weinberg equation for allele frequency?

p + q = 1

What do p and q represent in Hardy-Weinberg equilibrium?

p is the frequency of the dominant allele and q is the frequency of the recessive allele.

What is the Hardy-Weinberg equation for genotype frequencies?

p² + 2pq + q² = 1

What do p², 2pq, and q² represent?

p² is homozygous dominant, 2pq is heterozygous, and q² is homozygous recessive.

What are the five conditions required for Hardy-Weinberg equilibrium?

No mutations, random mating, no natural selection, extremely large population size, and no gene flow.

Why is Hardy-Weinberg equilibrium important?

It provides a baseline to determine whether evolution is occurring.

What is genetic drift?

Random changes in allele frequencies due to chance events.

Why does genetic drift have a stronger effect in small populations?

Random events can significantly change allele frequencies when the population is small.

What is the bottleneck effect?

A type of genetic drift caused by a sudden reduction in population size due to events like natural disasters.

What is the founder effect?

Genetic drift that occurs when a small group of individuals becomes isolated from a larger population and forms a new population.

What is gene flow?

The transfer of alleles between populations through migration of individuals or gametes.

How does gene flow affect populations?

It reduces genetic differences between populations.

What is mutation in terms of evolution?

A change in DNA that introduces new alleles into a population.

Why are mutations important for evolution?

They are the ultimate source of new genetic variation.

What is nonrandom mating?

When individuals choose mates based on certain traits rather than randomly.

Does nonrandom mating change allele frequencies?

No, but it changes genotype frequencies.

What is natural selection?

Differential survival and reproduction of individuals with advantageous traits.

What is directional selection?

Natural selection that favors individuals at one extreme of a phenotypic range.

What is stabilizing selection?

Selection that favors intermediate phenotypes and reduces variation.

What is disruptive selection?

Selection that favors individuals at both extremes of a phenotypic range.

What is sexual selection?

A form of natural selection where individuals with traits that improve mating success reproduce more.

What is sexual dimorphism?

Differences in appearance between males and females of the same species.

What is balancing selection?

Natural selection that maintains multiple alleles in a population.

What is heterozygote advantage?

When individuals heterozygous for a gene have higher fitness than either homozygous condition.

What is frequency-dependent selection?

Selection where the fitness of a phenotype depends on how common it is in the population