Several species of sea urchins may inhabit the same tide pool and their reproductive periods overlap. Although they practice external fertilization, they seldom interbreed because eggs produce chemicals that are only attractive to sperm of their own species. This is an example of a _________ barrier involving ________________.
A. prezygotic; geographic isolation
B. prezygotic; temporal isolation
C. prezygotic; gametic isolation
D. postzygotic; gametic isolation
E. postzygotic; hybrid infertility
Answer: C