The Natural World Series explores different world regions and the people and other living creatures that inhabit them. The central focus of each book is the region's wildlife — its animals, birds, and insects — how and where they live, their foods, and their social, mating, and breeding behaviors. Each page of every title in this series is filled with full-color illustrations. The earth's ocean environment is at least as complex as any on land. Its living creatures range in size from whales to plankton — drifting plants and animals of nearly microscopic size.