7.10 — Speciation & Reproductive Barriers

Reproductive Isolation

Populations can no longer successfully reproduce together to produce viable, fertile offspring.

Reproductive Compatibility

Ability of organisms to reproduce successfully with one another.

Allopatric Speciation

Formation of new species after geographic separation leads to reproductive isolation.

Geographic Isolation

Physical separation of populations.

Geographic Barrier

Physical feature that prevents or reduces movement between populations.

Sympatric Speciation

Formation of new species while populations remain in the same geographic area.

Polyploidy

Presence of extra complete chromosome sets; can cause rapid sympatric speciation, especially in plants.

Reproductive Barrier

Mechanism preventing successful reproduction between populations.

Prezygotic Barrier

Reproductive barrier acting before fertilization.

Postzygotic Barrier

Reproductive barrier acting after fertilization.

Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, Gametic Isolation

5 prezygotic reproductive barriers.

Habitat Isolation

Populations live in different habitats and rarely encounter each other for reproduction.

Temporal Isolation

Populations reproduce at different times.

Behavioral Isolation

Differences in courtship behavior or mating signals prevent mating.

Mechanical Isolation

Differences in reproductive anatomy prevent mating.

Gametic Isolation

Gametes cannot successfully fuse because of physical or biochemical incompatibility.

Reduced Hybrid Viability, Reduced Hybrid Fertility, Hybrid Breakdown

3 postzygotic reproductive barriers.

Reduced Hybrid Viability

Hybrid offspring fail to develop normally, die early, or cannot survive to reproduce.

Reduced Hybrid Fertility

Hybrid survives but cannot reproduce.