A population is all the organisms that both belong to the same group or species and live in the same geographical area. In ecology the population of a certain species in a certain area is estimated using the Lincoln Index. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals from other areas. Normally breeding is substantially more common within the area than across the border.
The biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth, a closed (apart from solar and cosmic radiation) and self-regulating system. From the broadest biophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere and atmosphere. The biosphere is postulated to have evolved, beginning through a process of biogenesis or biopoesis, at least some 3.5 billion years ago.
A community is a group of interacting living organisms sharing a populated environment.
A community is an assemblage of populations of different species, interacting with one another. Community ecology is the branch of ecology that studies interactions between and among species. It considers how such interactions, along with interactions between species and the abiotic environment, affect community structure and species richness, diversity and patterns of abundance. Species interact in three ways: competition, predation and mutualism. Competition typically results in a double negative - that is both species lose in the interaction. Predation is a win/lose situation with one species winning. Mutualism, on the other hand, involves both species cooperating in some way, with both winning.
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving (abiotic), physical components of the environment with which the organisms interact, such as air, soil, water and sunlight
Examples of ecosystems
Greater Yellowstone Ecosystem
Large marine ecosystem
Subsurface Lithoautotrophic Microbial Ecosystem
Urban ecosystem 2010 January 2012