What term refers to any factor that prevents mating between two different species?

• A. Gradualism
• B. Reproductive isolating mechanisms (RIMs)
• C. Anagenesis
• D. Cladogenesis

Answer: (B)

Reproductive isolating mechanisms are factors that prevent mating or fertilization between species, keeping their gene pools separate. These barriers can act before mating, such as differences in habitat, timing, or courtship signals, or after mating, such as hybrids that are sterile or inviable. Together, they describe anything that blocks interbreeding and maintains distinct species. The other terms refer to evolutionary patterns rather than barriers to mating: gradualism is slow, steady evolutionary change; anagenesis is evolution within a single lineage without branching; cladogenesis is the splitting of a lineage into distinct lineages. That’s why reproductive isolating mechanisms best answer the question.