The biosphere is part of the earth in which life exists. It is 20 km thick from the bottom of the ocean to the lower atmosphere. It consists of three layers: the lithosphere, which is the land on the surface of the earth; the hydrosphere, which comprises of the water on the earth as well as water vapor in the air; and the atmosphere, which is made up of the air that surrounds the earth. The living organisms in the biosphere interact and affect each other in many ways. This is called a biotic factor. Similarly, there are non-living elements that have an effect on living organisms, these are considered abiotic factors. Examples of abiotic factors are air, temperature, water, soil, light, and minerals.
             In a biosphere, organisms live in special groupings. For instance, a population consists of all individuals of a species living in a general area. A community is a population located in a certain area living among different species. An ecosystem is yet a larger conglomeration of a population, a community, and abiotic factors. Ecosystems can be aquatic or terrestrial. The earth's aquatic ecosystem makes up about 75% of the earth's surface. This aquatic environment is divided into marine and freshwater environments. The earth's terrestrial ecosystem is mainly made up of forests and deserts, which make up for 25% of the earth's surface.
             The role or function of an organism in a community is that organism's niche. An organism's niche is an area picked by that organism based on physical factors such as temperature, light, oxygen and carbon dioxide content and biological factors such as food, competition for resources and predators. This niche provides the organism a place to live in. A habitat remains consistent with an organism's niche as well as provides the organism with a place to reproduce. In this case, organisms may have the same habitat, but different niches.
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