Natural Selection and Speciation Concepts

These flashcards cover key vocabulary and concepts related to natural selection, speciation, and genetic variation.

Natural Selection

Process where individuals with traits that enhance survival or reproduction leave more offspring, changing allele frequencies over generations.

Fitness

An organism’s ability to survive and reproduce in its environment.

Adaptation

A heritable trait that increases an organism’s fitness.

Acclimation

A reversible physiological or behavioral change within an organism’s lifetime; does not involve genetic change.

Stabilizing Selection

Selection favoring intermediate traits; extremes are selected against.

Directional Selection

Selection favoring one extreme trait over others.

Diversifying Selection

Selection favoring two or more extreme traits over intermediate traits.

Mutation

A random change in DNA sequence that can create new alleles; source of genetic variation.

Genetic Variation

Differences in DNA sequences among individuals in a population.

Phenotypic Variation

Differences in observable traits among individuals.

Gene Flow

Movement of alleles between populations through migration or mating; increases genetic similarity and diversity.

Genetic Drift

Random changes in allele frequencies due to chance events; especially strong in small populations.

Founder Effect

When a small group establishes a new population, limiting allele diversity.

Bottleneck Effect

Sharp reduction in population size, leading to loss of genetic diversity and possible fixation of alleles.

Inbreeding

Mating among closely related individuals; increases expression of harmful alleles.

Speciation

Formation of new species from an ancestral population.

Allopatric Speciation

Speciation due to a physical/geographic barrier separating populations.

Sympatric Speciation

Speciation without a physical barrier; usually due to ecological or behavioral differences.

Prezygotic Isolation

Barriers preventing fertilization (no egg or sperm fusion).

Postzygotic Isolation

Fertilization occurs, but offspring have reduced fitness or fertility.

Biological Species Concept

Defines species as populations that can interbreed and produce fertile offspring.

Morphological Species Concept

Defines species based on physical similarities and differences.

Phylogenetic Species Concept

Defines species based on evolutionary history and shared ancestry.

Evolution

Change in allele frequencies in a population over time.

Interspecific Competition

Competition between different species.

Intraspecific Competition

Competition within the same species.