What are five reproductive barriers?

Answer 1

Five reproductive barriers are habitat isolation, temporal isolation, gametic isolation, hybrid breakdown, and reduced hybrid fertility.

Habitat isolation, temporal isolation, and gametic isolation are examples of prezygotic reproductive barriers, meaning that they impede mating or hinder fertilization if mating does occur.

Habitat isolation: Even if two species live in the same area, if they live in different habitats (ex: land vs. water), then they may rarely encounter each other and thus not be able to reproduce together.

Temporal isolation: If a species breeds at different times (different days, seasons, years, etc), then they will not be able to mix their gametes.

Gametic isolation: Gametic isolation occurs when the one species' sperm cannot fertilize another species' eggs. This isolation can be produced in a variety of ways such as the sperm's inability to survive the reproductive tract in the other species' females and biochemical mechanisms that prevent the sperm from penetrating the other species' eggs.

Hybrid breakdown and reduced hybrid fertility are examples of postzygotic barriers since they prevent a hybrid zygote from developing into a viable, fertile adult.

In hybrid breakdown, the first-generation of hybrids are fertile. However, when they reproduce (either by mating with one another or with one of their parent species), the next generation's offspring are feeble and sterile.

In reduced hybrid fertility, the hybrids are sterile such as that of a cross between a donkey and a horse-a mule. This can happen if the two parent species have chromosomes with different structures because meiosis will fail to produce normal gametes in the hybrids. As a result, when the hybrids mate with either of their parental species, they cannot produce offspring. Thus, genes cannot freely flow between the species as the hybrids are infertile and cannot reproduce.