Evolution and Speciation · Paper 1 — Free Biology HL Practice Questions

A river forms through a forest habitat, physically separating two populations of a small rodent species. Over many generations, the isolated populations diverge in fur colour and mating calls. Which statement most accurately describes the mechanism of speciation occurring here?

Two populations of cichlid fish undergo allopatric speciation after a land bridge divides their lake for 10,000 years. When the lake reconnects and individuals from both populations are placed together, the females of each population only respond to the courtship displays of males from their own population, so fertilisation never occurs. Which type of reproductive isolating mechanism does this represent?