Biosphere

The biosphere is the part of the Earth and its atmosphere in which living organisms are found. It is made up of all the ecosystems on Earth, and includes the lower atmosphere, the land surface and soil, and all the water in oceans, lakes and rivers.The biosphere is a thin layer. Most life is found within a few kilometres of the Earth's surface, although bacteria have been found deep in rocks and spores high in the atmosphere.The biosphere is the highest level of organisation in ecology:organism → population → community → ecosystem → biome → biosphereA biome is a large region with a characteristic climate and type of community, such as tropical rainforest, desert, tundra or grassland. Similar biomes occur on different continents where the climate is similar.Energy enters the biosphere as sunlight and leaves as heat radiated to space, so the biosphere is open to energy. For matter it is almost closed: the same atoms of carbon and nitrogen, and the same water, are cycled over and over between organisms, the atmosphere, oceans and rocks.Because all ecosystems are linked through these cycles and through the atmosphere and oceans, human activities in one place can affect the whole biosphere. For example, carbon dioxide released by burning fossil fuels in one country mixes through the atmosphere and contributes to global warming everywhere.