My Science Box explains that Earth is a biosphere, as it is a global sum of all ecosystems. A biosphere is a closed system containing various zones of life. All living organisms within a biosphere are organized into various layers of complexity. These layers extend from the individual, to populations and communities, to ecosystems and biomes.
A population contains all of the individuals of a species living and interbreeding within the confines of a specific area. Multiple types of organisms inhabiting a given area make up a biological community. The populations within a community are interdependent because of the food chain that links them together. The next level of organization is an ecosystem, which consists of all living things in a particular area, plus all the non-living components of the environment. Non-living components include such things as soil, water, atmospheric gas and light. Ecosystems can be divided into major biomes, which are characterized by a specific type of geography, vegetation and climate. Biomes on Earth include tundras, deserts, prairies, deciduous forests, tropical rainforests and oceans.
Although two ecosystems of Earth may share the same biome characteristics, the organisms inhabiting these separate ecosystems differ. For example, all rainforests have similar features anywhere in the world, containing large trees, vines and many animal species. However, the exact species of trees and animals vary from rainforest to rainforest. These organisms may be similar in form, but often descend from different evolutionary backgrounds. The summation of all of Earth's ecosystems and its various zones of life makes up the biosphere.