Lesson 22: Macroevolution and Speciation

Adaptive Change

Evolutionary modification that improves an organism’s ability to survive and reproduce in its environment.

Adaptive Radiation

Rapid diversification of a single ancestral species into multiple species adapted to different ecological niches.

Allopatric

Speciation that occurs when populations are geographically separated.

Behavioral Isolation

A prezygotic barrier where differences in mating behaviors prevent interbreeding between species.

Biological Species Concept

Defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups.

Ecological Isolation

A prezygotic barrier where species occupy different habitats within the same area, preventing mating.

Gene Flow

Movement of alleles between populations through migration or interbreeding.

Genetic Drift

Random changes in allele frequencies, especially in small populations, leading to evolutionary change.

Geographic Isolation

Physical separation of populations by barriers such as mountains or rivers, leading to allopatric speciation.

Gradualism

The hypothesis that evolution occurs slowly through small, incremental changes over long periods.

Hybrid Infertility

A postzygotic barrier where hybrid offspring survive but cannot reproduce.

Hybrid Inviability

A postzygotic barrier where hybrid embryos fail to develop or die early.

Hybridization

The process of interbreeding between individuals from different species or populations.

Mechanical Isolation

A prezygotic barrier where differences in reproductive structures prevent successful mating.

Phylogenetic Species Concept

Defines species based on the smallest group of individuals sharing a common ancestor, forming one branch on the tree of life.

Postzygotic Isolation

Reproductive barriers that occur after fertilization, reducing hybrid viability or fertility.

Prezygotic Isolation

Reproductive barriers that prevent fertilization from occurring.

Punctuated Equilibrium

The hypothesis that evolution occurs in rapid bursts of change followed by long periods of stability.

Reinforcement

Natural selection strengthens reproductive barriers, reducing hybrid formation.

Reproductive Isolation

The inability of two populations to interbreed and produce fertile offspring.

Reproductively Isolated

Describes populations that cannot exchange genes due to reproductive barriers.

Speciation

The process by which new species arise from existing ones.

Species

A group of organisms that can interbreed and produce fertile offspring under natural conditions.

Subspecies

Populations within a species that differ in traits but can still interbreed.

Sympatric

Speciation that occurs without geographic separation, often through ecological or behavioral isolation.

Temporal Isolation

A prezygotic barrier where species reproduce at different times, preventing interbreeding.