A comprehensive look is taken into how mountain ranges, perpetual night, pressure and temperature extremes create unusual life forms.

Emperor penguin chicks born on the ice in winter are abandoned by their parents in the spring, so they must navigate their way across the sea ice.

David explores Earth's precious freshwater reserves to observe the incredible animals that inhabit it.

Rare pygmy three-toed sloths live peacefully; predators pose little threat to albatrosses; young marine iguanas fight for survival the moment they hatch.

In the green seas of the Earth, sunlight brings life to vast kelp forests, mangroves, seagrass prairies and algae blooms, and animals fight for space and food.

Clever meerkats encounter an even smarter bird; black rhinos meet for a surprisingly social gathering; aggressive giraffes fight over the limited resources.