A habitat, or biome, is the type of environment in which plant and animals live. Habitat is dictated by what kinds of plants grow there, the climate and the geography. Rainforest, coral reefs and the tundra are all habitats where particular kinds of plants and animals might be found.
Terrestrial habitats include forests, grasslands, deserts and rainforests. They are typically defined by factors such as plant structure (trees and grasses), leaf types (eg broadleaf and needleleaf), plant spacing (forest, woodland, savanna) and climate.
Freshwater habitats include bogs, ponds, lakes, rivers and streams. About 3% of Earth's water is freshwater, but this includes the water locked up in the ice caps and trapped in rocks and soil as groundwater. Only a tiny fraction (0.014%) is surface water in the form of rivers, lakes and swamps.
Approximately 71% of the Earth's surface is covered by the oceans, an area of some 223698816km/sq. Although marine life evolved around three billion years before life on land, marine habitats are relatively poorly studied and much of the ocean's depths remains unexplored.