Chapter 24 Notes: The Origin of Species

Reproductive Isolation

Biological barriers prevent interbreeding and production of viable, fertile offspring.

Prezygotic Barriers

Block fertilization by impeding mating attempts, preventing completion of mating, or hindering fertilization.

Habitat Isolation

Species in different habitats rarely encounter each other.

Temporal Isolation

Species breed at different times.

Behavioral Isolation

Unique courtship rituals prevent mating.

Mechanical Isolation

Morphological differences prevent mating completion.

Gametic Isolation

Sperm and eggs of different species bind poorly, preventing zygote formation.

Postzygotic Barriers

Prevent hybrid zygotes from developing into viable, fertile adults.

Reduced Hybrid Viability

Hybrid development or survival is impaired.

Reduced Hybrid Fertility

Meiosis fails, resulting in sterile hybrids.

Hybrid Breakdown

First-generation hybrids are viable, but later generations are feeble or sterile.

Allopatric Speciation

Speciation due to geographic isolation.

Sympatric Speciation

Speciation in the same geographic area.

Polyploidy

Extra sets of chromosomes cause a new species in one generation.

Autopolyploid

More than two sets of chromosomes derived from a single species.

Allopolyploid

More than two sets of chromosomes derived from different species.

Sexual Selection

Mate choice drives sympatric speciation.

Habitat Differentiation

Exploitation of new habitats or resources leads to sympatric speciation.