For ten hours, a narrator (David Attenborough) takes viewers through the challenges of life, showing how animals and plants have evolved, starting with reptiles and amphibians, the earliest creatures on Earth. Other great species under study are fish and other varieties of aquatic life in the seas and waters of the planet, followed by the creatures of the air who fly, as well as birds that are land-bound. Time is also given over to insects that outnumber all other animals by far. Featured too is an examination of hunters and hunted, how prey can eat or be eaten. Invertebrates in the deep oceans around the world, as well as plant varieties, and primates, round out the examination of life forms on the planet.