Believe it or not, but ducks have a reputation for the unexpected: bizarre and intricate mating anatomy. According to ...

Medically reviewed by Andrea L. Braden, MD Key Takeaways The female reproductive system includes organs that produce hormones like estrogen and progesterone. Ovaries release one mature egg each month ...

In a bizarre twist of evolution, some fish have been found to be able to control which sperm fertilizes their eggs in order to have the best offspring. According to a study published in the journal ...

The cellular biology of reproduction is often depicted as an epic journey, in which millions of intrepid sperm fight to be the first to claim the ultimate prize: the chance to fertilize the egg, which ...