In these science fiction books, extraterrestrial beings are sympathetic, horrifying and everything in between.

This semi-aquatic mammal may look improbable, but its biology reveals how evolution shapes even the strangest mammal bodies.

Scientists discovered that making a very small change to female mice's DNA caused them to develop male reproductive organs.

The hectocotylus is both a reproductive organ and a sensory organ, a rare combination in animals, new research suggests ...