700 million years ago, a remarkable creature emerged for the first time. Though it may not have been much to look at by today’s standards, the animal had a front and a back, a top and a bottom. This ...

Embryonic germ layers are the fundamental organizing principle in animal development. They provide the structural basis from which tissues and organs arise. During early embryogenesis, cells divide to ...

When people build cities and introduce invasive creatures, resident critter populations sometimes adapt Brian Handwerk | Science Correspondent Several species have evolved in response to human ...