AP Biology Chapter 24 Terms and Definitions

Allopatric Speciation

Speciation that occurs when populations are separated by a geographic barrier.

Behavioral Isolation

Differences in courtship or mating behaviors that prevent organisms from reproducing.

Biological Species Concept

Defines a species as a group of organisms that can interbreed and produce fertile offspring.

Ecological Species Concept

Defines a species based on its ecological niche or role in the environment.

Gametic Isolation

When sperm and egg cannot successfully fuse during fertilization.

Habitat Isolation

When populations live in different habitats and therefore rarely encounter each other to reproduce.

Hybrid

Offspring produced by parents from two different species or genetically distinct populations.

Hybrid Breakdown

When hybrid offspring are healthy and fertile but their offspring have reduced viability or fertility.

Hybrid Zone

A geographic area where two different populations or species meet and produce hybrids.

Macroevolution

Evolutionary change that occurs at or above the species level, including the formation of new species.

Mechanical Isolation

When differences in reproductive structures prevent successful mating or transfer of gametes.

Microevolution

Changes in allele frequencies within a population over generations.

Morphological Species Concept

Defines a species based on physical characteristics and appearance.

Paleontological Species Concept

Defines species based on differences in physical characteristics observed in the fossil record.

Phylogenetic Species Concept

Defines a species as the smallest group sharing a common ancestor and distinct evolutionary history.

Postzygotic Barrier

A reproductive barrier that occurs after fertilization and reduces the survival or fertility of offspring.

Polyploidy

A condition in which an organism has more than two complete sets of chromosomes.

Prezygotic Barrier

A reproductive barrier that prevents fertilization from occurring.

Punctuated Equilibrium

A model of evolution in which species remain relatively unchanged for long periods followed by short periods of rapid evolutionary change.

Reduced Hybrid Fertility

When hybrid offspring survive but are unable to reproduce successfully or have reduced fertility.

Reduced Hybrid Viability

When hybrid offspring have reduced survival or are less likely to survive and reproduce.

Reinforcement

Natural selection that strengthens reproductive barriers between populations because hybrids have lower fitness.

Reproductive Isolation

When populations cannot successfully reproduce with each other and produce fertile offspring.

Speciation

The evolutionary process through which new species form.

Species

A group of organisms that can interbreed and produce viable, fertile offspring.

Sympatric Speciation

Speciation that occurs without geographic separation between populations.

Temporal Isolation

When populations reproduce at different times, preventing them from mating.