What is reproductive isolation in evolutionary biology?

• A. The ability of a species to interbreed with all other species.
• B. The genetic similarity shared by all individuals within a species.
• C. Barriers that prevent interbreeding between populations, facilitating the formation of new species.
• D. The process by which populations migrate to new habitats.

Answer: (C)

Reproductive isolation describes the barriers that prevent two populations from producing viable, fertile offspring. These barriers can be prezygotic, like differences in mating times, behaviors, or habitats, or mechanical or gametic incompatibilities that stop fertilization. They can also be postzygotic, where even if mating occurs, the offspring are weak, infertile, or fail to survive. By preventing gene flow between populations, these barriers allow genetic differences to accumulate, leading to the formation of new species over time. This concept explains how species remain distinct and diverge when populations are separated. The other ideas describe general genetic similarity within a species, or the ability to interbreed with many others, or movement between habitats—none of which capture the idea of barriers to reproduction driving speciation.