What are the reproductive barriers that keep species separate?

a. lack of food; lack of habitat; lack of potential mates; lack of nesting sites; lack of genetic variation

b. mountains; canyons; glaciers; bodies of water (for terrestrial animals); areas of land (for aquatic animals)

c. habitat isolation; temporal isolation; behavioral isolation; mechanical isolation; gamete isolation

C. habitat isolation; temporal isolation; behavioral isolation; mechanical isolation; gamete isolation.

Explanation:

Reproductive Barriers may be of any type which includes habitat isolation; temporal isolation; behavioral isolation; mechanical isolation; gamete isolation. All these examples are categorized under prezygotic barriers.

Habitat isolation: It occurs in case of allopatric speciation, initially all the members of a species can mate with each other but later on due to geographic barriers like due to a rift, their habitat separates and they cannot mate with each other and later on they evolve as separate species.

Temporal isolation: In temporal isolation, reproductive barrier is different time/season of breeding like American toads and Fowler's toad both are closely related and have potential to mate but due to different mating season they are unable to mate with each other. American toads mate during summers while Fowler's toad mate during late summers.

Behavioral isolation: When the members of two closely related species behave and respond to different mating behavior, it is known as behavioral isolation. For example breeding calls.

Mechanical isolation: Mechanical isolation occurs because of structural or chemical barriers. For example: when the shape of pollinator does not match with that of flower then the male gametes will not be able to reach to the egg cell.

Gamete isolation: When the gametes are unable to fuse due to any reason like less mobility of sperm in the female reproductive tract.