A habitat is an area with certain physical characteristics which support a particular community of animals and plants. In general, a habitat can be defined in physical terms, e.g., a rocky seashore or sandy desert, but as far as any one animal or plant species is concerned, the habitat cannot be defined without reference to the other animals and plants in the community.
A critical habitat is a habitat that is critical for the existence of an endangered species.
Zonation is the occurrence of bands of characteristic vegetation in an area. Examples include the bands of different types of seaweed that occur progressively up a shore from the low-tide to the high-tide levels. Species from the low-tide zone would dry out and die at the high-tide level, whereas high-tide species could not withstand prolonged immersion in seawater in the low-tide zone. The varying vegetation in turns attracts varying animal species.