"We may all be netted together" - Darwin. This picture is a great way to illustrate and explain the relations/interactions within all animals. Does not necessarily relate to sexual selection, but a good representation of all Darwin theorized of.
Charles Darwin. "It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change” . . . "If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.”