Ch. 23: Mechanisms of Evolution and Population Genetics

Natural Selection

Process where organisms better adapted survive.

Genetic Drift

Random changes in allele frequencies in populations.

Mutation

Changes in DNA sequence creating genetic diversity.

Gene Flow

Transfer of genes between populations through migration.

Sexual Selection

Preference for certain traits in mate selection.

Natural Selection

Process where individuals with advantageous traits survive.

Microevolution

Small-scale evolution; allele frequency changes in populations.

Allele

Variant of a gene at a specific genomic location.

Genetic Drift

Random changes in allele frequencies due to chance.

Gene Flow

Transfer of alleles between different populations.

Genetic Variation

Differences in genes among individuals in a population.

Phenotype

Observable traits resulting from genotype and environment.

Heterozygous Loci

Loci with two different alleles in an individual.

Nucleotide Variability

Differences in nucleotide sequences among individuals.

Point Mutation

Change in a single nucleotide in DNA sequence.

Heterozygote Protection

Recessive harmful mutations hidden in heterozygous individuals.

Neutral Variation

Genetic variation with no selective advantage or disadvantage.

Mutation

Change in DNA sequence that can create new alleles.

Rapid Reproduction

Fast generation times lead to quick accumulation of mutations.

Crossing Over

Exchange of genetic material during meiosis.

Independent Assortment

Random distribution of chromosomes into gametes.

Fertilization

Random combination of gametes from parents.

Hardy-Weinberg Equation

Mathematical formula to test population evolution.

Hardy-Weinberg Assumptions

Conditions for a population to remain in genetic equilibrium.

Seed Shortage Example

Medium ground finches evolved larger beaks for survival.

Environmental Influence

External factors affecting phenotypic variation.

Mendel's Work

Established principles of heredity through pea plant studies.

Population

Group of interbreeding individuals in the same area.

Gene Pool

All alleles at every locus in a population.

Locus

Specific location of a gene on a chromosome.

Homozygous

Having identical alleles for a gene.

Heterozygous

Having different alleles for a gene.

Genotype Frequency

Proportion of each genotype in a population.

Allele Frequency

Proportion of each allele in a population.

Diploid Organisms

Organisms with two alleles per locus.

Hardy-Weinberg Equilibrium

Stable allele frequencies in a non-evolving population.

Natural Selection

Differential survival and reproduction based on traits.

Genetic Drift

Random fluctuations in allele frequencies.

Founder Effect

Allele frequency changes due to a small founding population.

Bottleneck Effect

Reduction in population size affecting genetic diversity.

Gene Flow

Movement of alleles between populations.

Relative Fitness

Contribution to the next generation's gene pool.

Directional Selection

Favors one extreme phenotype in a population.

Disruptive Selection

Favors both extreme phenotypes over intermediates.

Stabilizing Selection

Favors intermediate phenotypes, reducing variation.

Sexual Selection

Selection based on traits that enhance mating success.

Intrasexual Selection

Competition among the same sex for mates.

Intersexual Selection

Mate choice based on traits of the opposite sex.

Good Genes Hypothesis

Females choose mates based on genetic quality.

Balancing Selection

Maintains multiple phenotypes at stable frequencies.

Frequency-dependent Selection

Fitness of a phenotype depends on its frequency.

Heterozygote Advantage

Heterozygotes have higher fitness than homozygotes.

Adaptive Evolution

Increase in traits enhancing survival over time.

Mendelian Segregation

Separation of alleles during gamete formation.

Mutation

Random changes in DNA affecting allele frequencies.