Question

Reproductive isolation can occur in a number of ways, but the net effect is always the same in that:
(A) Hybridisation must take place before new species can form.
(B) It causes geographic isolation between organisms.
(C) The rate of speciation slows down.
(D) Few or no genes flow between populations.

Answer 1

Hint: Reproductive isolation occurs when barriers or variations in geography, behaviour, physiology, or genetics prevent a species from effectively mating with other species that are related to it.

Step by step solution:
 As populations' genomes coalesce into the distinct adaptive entities we identify as species, reproductive isolation increasingly becomes a trait of the genome rather than of individual genes. Reproductive isolation is the breakdown of an organism's ability to effectively reproduce with sexual partners of a different kind of organism, and speciation involves the development of reproductive isolation between diverging forms of the organism until gene flow is sufficiently infrequent. Reproductive isolation enables organisms to develop into unique species that cannot interbreed once their populations are once again contiguous. Behavioural, spatial, and temporal isolation are just a few of the ways that reproductive isolation can manifest. The creation of new species by any means, be it isolation or anything else such as mutation, is known as speciation.
 It appears that there are five main categories of prezygotic barriers to reproduction: geographical, temporal, mechanical, gametic, and behavioural barriers. Reproductive isolation barriers fall into two basic categories: Before fertilization can take place, prezygotic isolation takes place (no offspring are produced) After fertilization, there is postzygotic isolation (offspring are either not viable or infertile)
Hence, option (D) is correct.
Note: Since there is no gene flow due to reproductive isolation, potential trait divergence that could eventually result in speciation is made conceivable.