"The Sopranos" have some competition - brown-headed cowbirds.

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive. Yet sperm can be very long lived, while eggs degenerate quickly after they are made if they are not fertilized .

Marine turtles almost always return to the same beach to lay their eggs. The egg-laying sites are often far from the feeding areas and the females cross several hundred kilometers of ocean with no visual landmarks.

Air pollution sources are everywhere in the home, from the bacon and eggs frying in the kitchen, to the woodburning stove in the family room, the newly painted hallway, and even the carpet in the living room.

Australian scientists are raising concerns over the unpredictable nature of a contraceptive vaccine that aims to control populations of wild animals, such as rabbits and foxes.

Individual sperm in promiscuous rodents have learned to work together in order to compete against sperm of rival males, according to new research carried out at the University of Sheffield

A decade ago, Shuhai Xiao, associate professor of geosciences at Virginia Tech, and his colleagues discovered thousands of 600-million-year-old embryo microfossils in the Doushantuo Formation, a fossil site near Weng'an, South China. In 2000, Xiao's team reported the discovery of a tubular coral-like animal that might be a candidate for parenthood.

A study from the February issue of the American Naturalist is the first to demonstrate that male fish are more likely to eat their offspring when they have been cuckolded during the act of spawning. Moreover, the more males that are present during spawning, the more likely it is that a male will try to eat the eggs when they are laid, as it is less likely that he fertilized them.