Which of the following reproductive barriers actually prevents individuals of sibling species from copulating?

Question

A. hybrid inviability

B. hybrid sterility

C. gametic isolation

D. hybrid breakdown

E. mechanical isolation

Answer 1

The answer is E.  Mechanical isolation is when there is a physical difference between species that prevents them from actually peforming the act.  

Gametic isolation is when copulation can occur, but the sperm can't fuse with the egg.

A,B, and D are all examples of reproductive isolation where fertilization can occur but at some point the offspring are no longer viable.

Answer 2

E -- if they can't get at each other, they can't copulate.