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

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

Evolution occurs slowly and steadily over long periods through the accumulation of small changes.

Evolution happens in bursts, with long periods of stasis interrupted by short periods of rapid change.

Rapid diversification of a species into many new forms, often after new habitats become available.

Speciation that occurs when populations are separated by a geographical barrier, preventing interbreeding.

Speciation that occurs within the same geographic area due to disruptive selection or mating preferences.

Mechanisms that prevent fertilization from occurring in the first place.

Mechanisms that prevent the formation of fertile offspring after fertilization has occurred.

It can lead to allopatric speciation as the isolated populations evolve independently.

It can lead to sympatric speciation if different phenotypes are favored in different parts of the habitat.

Prevents mating or fertilization, thus preventing the formation of a hybrid zygote.

Allows a hybrid zygote to form but results in offspring that are infertile or have reduced viability.

Gradualism: Slow, steady change over time. Punctuated Equilibrium: Bursts of rapid change separated by long periods of stasis.

Allopatric: Geographic separation. Sympatric: No geographic separation, occurs in the same area.

Prezygotic: Prevents fertilization. Postzygotic: Occurs after fertilization, results in infertile offspring.