CH 23:Evolution of Populations: Mechanisms, Natural Selection, and Genetic Variation

Microevolution

Small-scale changes in allele frequencies within a population over time.

Natural selection

A mechanism of evolution where individuals with favorable traits are more likely to reproduce.

Genetic drift

Random changes in allele frequencies in a population, often having a more significant effect in smaller populations.

Gene flow

The transfer of alleles or genes from one population to another.

Genetic variation

Differences in alleles among individuals in a population.

Mutations

Formation of new alleles, introducing variation into a population.

Gene duplication

Duplications of large chromosome segments, usually harmful, but smaller DNA piece duplications can play a major role in evolution.

Olfactory genes

Genes that enable mammals to distinguish among many different chemicals, enhanced by gene duplication.

Rapid Reproduction

Shorter generation times allow mutations to accumulate rapidly.

Clostridium

A bacterium that reproduces every 20 minutes.

Locus

The specific location of a gene on a chromosome.

Diploid

A cell or organism with two sets of chromosomes.

Haploid

A cell or organism with one set of chromosomes.

Genotype

The genetic constitution of an individual.

Phenotype

The observable physical or biochemical characteristics of an individual.

Alleles

Versions of genes.

Population

All of the individuals of the same species that live in a particular place at the same time.

Gene Pool

All copies of every allele at every locus in the whole population, characterized by allelic frequencies.

Allele frequency

Percentage of a specific allele of a given gene locus in the population.

Genetic equilibrium

Condition where allele and genotype frequencies remain constant across generations.

Hardy-Weinberg Equation

Provides a baseline for comparing actual populations to determine if they are evolving.

Hardy-Weinberg Equilibrium

A state where a population is not changing, requiring no mutations, random mating, no gene flow, extremely large populations, and no natural selection.

Ancestral population

The original population from which later populations descend.

Allele frequencies

The proportion of different alleles of a gene in a population.

Mutation

A new genetic variant that appears in a population.

Nonrandom Mating

A mating pattern that affects genotype frequency but does not change allele frequencies.

Migration

The physical flow of alleles between populations, also known as gene flow.

Founder Effect

The establishment of a new population by a small number of individuals from a larger population.

Genotype frequency

The proportion of different genotypes in a population.

Random mating

A mating pattern where individuals pair by chance, not influenced by genotype or phenotype.

Inbreeding

Mating between closely related individuals, which can lead to reduced genetic diversity.

Allele

A variant form of a gene.

Isolation

Separation of populations that can lead to reduced gene flow.

Adaptation

The process by which a species becomes better suited to its environment.

Chance event

An occurrence that can randomly affect allele frequencies in a population.

Small populations

Populations that have a limited number of individuals, which can lead to genetic drift.

Pollutant

A substance that can harm organisms, affecting allele frequencies by selectively killing certain genotypes.

Hardy-Weinberg condition

A set of conditions under which allele frequencies in a population remain constant over generations.

Allele frequencies change

Alterations in the proportion of different alleles in a population due to evolutionary mechanisms.

Culex pipiens

A species of mosquito that has shown global spread of insecticide resistance alleles.

Banded patterns

A physical trait observed in mainland snakes that is favored by natural selection.

Modification of Prevailing Conditions

Environmental change that affects natural selection.

Overproduction

Excess progeny produced by a population.

Relative Fitness

The success of an individual in passing on its genes compared to others in the population.

Directional Selection

A type of selection that favors one extreme phenotype over others.

Resistance

An example of directional selection.

Beak Morphology Shift

The evolution of longer and larger beaks in Anna's Hummingbirds due to environmental changes.

Mechanism of Selection

The process by which certain traits are favored in a population due to selective pressures.

Sexual Selection Component

The selection of traits based on their role in courtship and competition for mates.

Thermoregulatory Trade-Offs

Adaptations in beak morphology to conserve heat in colder regions.

Rapid Evolution

Evolutionary changes that occur quickly in response to environmental changes.

Stabilizing Selection

Selection that favors intermediate phenotypes and acts against extremes.

Disruptive Selection

Selection that favors extreme phenotypes over intermediate ones.

Sexual Selection

The process by which individuals select mates based on desirable traits.

Courtship Displays

Behavioral displays used by individuals to attract mates.

Greater Prairie Chicken Male Dance and Behavior

A specific courtship display used by male Greater Prairie Chickens.

Elaborate Decoration of Males

Physical traits developed in males to attract females.

Male vs Female Bees

Differences in physical traits between male and female bees.

Anna's Hummingbird

A species studied for its evolutionary changes in beak morphology.

Environmental Change

Alterations in the environment that can affect natural selection.

Selective Pressure

Factors that influence the survival and reproduction of individuals in a population.

Genetic Characteristics

The inherited traits that define a population.