Species is a group of interbreeding individuals. In natural selection, members may inherit a genetic change that makes them better suited to a particular environment. Consequently, these members are more likely to produce more surviving offspring. Adaptations to different ways of life explain diversity of life forms. Populations within a community interact among themselves and with the physical and chemical environment, forming an ecosystem.
All ecosystems together make up the biosphere, the thin layer of life that encircles the earth.
Interactions between populations in an ecosystem tend to keep the system relatively stable. Food relationships form a major part of interaction between populations. A constant supply of solar energy is required for an ecosystem and for life to exist. Require plentiful sun and rainfall all year long. Human populations tend to modify existing ecosystems for own purposes.