Final answer:
Reproductive isolation refers to when members of a species are unable to successfully mate with members outside their species, preventing gene flow. There are prezygotic and postzygotic barriers that contribute to reproductive isolation.
Step-by-step explanation:
Reproductive isolation refers to the situation in which members of a species are unable to successfully mate with members outside their species. It prevents gene flow between different species, which is the movement of genetic material from one population to another. There are different types of reproductive isolation, including prezygotic barriers that prevent fertilization from taking place and postzygotic barriers that occur after zygote formation, such as organisms that don't survive the embryonic stage or are born sterile.