You are studying two species of birds, both of which form monogamous pairs one male and one female). In species 1, you find that the eggs in a pair's nest are in fact almost always the offspring of that pair. In species 2, you are surprised to find that many of the eggs in a nest were actually fathered by males of neighboring pairs. Apparently, mating outside of monogamous pairings is widespread in species 2. Given this information, what would be the logical prediction to make before comparing testis size of males of the two species?
A) Testes of species 2 are larger than testes of species 1.
B) Testes of species 1 are larger than testes of species 2.
C) There is no relationship between this observation and the size of testes.

Question

Quizplus · Accepted Answer

In species where mating outside of monogamous pairings is widespread, males typically have larger testes as a result of sperm competition. Since species 2 engages in such behavior more than species 1, it would be logical to predict that males of species 2 have larger testes.

You Are Studying Two Species of Birds, Both of Which