External fertilization, however, seems to be a more recent development in sexual strategies than the more intimate alternative—internal fertilization. According to research published yesterday ...

The female reproductive system is a complex system of external and internal organs that produce eggs that are necessary for reproduction. One egg is prepared for fertilization every month.

Until now, biologists had no idea that the switch from internal to external fertilization was evolutionarily possible. Placoderms were previously considered by some to be an evolutionary dead end ...

They reproduce sexually through external fertilization (releasing eggs and sperm into the water) and internal fertilization ...