In ecology, a community refers to a grouping of species living collectively and interactively with the environment in a specified area, while the term biosphere refers to the total extent of all of the ecological systems on Earth. The natural communities in an ecosystem can change in a process referred to as succession, which can encompass lengths of time ranging between a few years and centuries. In the biosphere, the totality of living organisms on Earth have been interacting with each other and the elements of the hydrosphere, lithosphere and atmosphere for what is believed to be a span of about 3.5 billion years.
The process of change, or succession, that takes place in an ecological community can be of two types: primary and secondary. In a primary succession a community develops in a newly exposed landform where none existed before, while in a secondary succession, a replacement community colonizes an ecosystem that was recently damaged or destroyed by an upheaval, such as a forest fire or flood.
In the global ecological closed system of the biosphere, the variety of ecological systems are divided into biomes by geographic regions. Some examples of biomes are the aquatic biomes, such as lakes, streams and wetlands, and the terrestrial biomes, such as forests, deserts and grasslands. Every portion of Earth contains life of some sort, including what were once thought to be uninhabitable zones below the Earth's surface. Those biomes that lie on or close to the equator contain the largest community populations of plant and animal species.