Scope

Ecology is usually considered as a branch of biology, the general science that studies living organisms. Organisms can be studied at many different levels, from proteins and nucleic acids (in biochemistry and molecular biology), to cells (in cellular biology), to individuals (in botany, zoology, and other similar disciplines), and finally at the level of populations, communities, and ecosystems, to the biosphere as a whole; these latter strata are the primary subjects of ecological inquiry. Ecology is a multidisciplinary science. Because of its focus on the higher levels of the organization of life on earth and on the interrelations between organisms and their environment, ecology draws on many other branches of science, especially geology and geography, meteorology, pedology, genetics, chemistry, and physics. Thus, ecology is considered by some to be a holistic science, one that over-arches older disciplines such as biology which in this view become sub-disciplines contributing to ecological knowledge. In support of viewing ecology as a subject in its own right as opposed to a sub-discipline of biology, Robert Ulanowicz stated that "The emerging picture of ecosystem behavior does not resemble the worldview imparted by an extrapolation of conceptual trends established in other sciences."

Agriculture, fisheries, forestry, medicine, and urban development are among human activities that would fall within Krebs' (1972: 4) explanation of his definition of ecology: where organisms are found, how many occur there, and why.

Ecological knowledge such as the quantification of biodiversity and population dynamics has provided a scientific basis for expressing the aims of environmentalism and evaluating its goals and policies. Additionally, a holistic view of nature is stressed in both ecology and environmentalism.

Consider the ways an ecologist might approach studying the life of honeybees:

• The behavioral relationship between individuals of a species is behavioral ecology — for example, the study of the queen bee, and how she relates to the worker bees and the drones.

• The organized activity of a species is community ecology; for example, the activity of bees assures the pollination of flowering plants. Beehives additionally produce honey which is consumed by still other species, such as bears.
• The relationship between the environment and a species is environmental ecology — for example, the consequences of environmental change on bee activity. Bees may die out due to environmental changes (see pollinator decline). The environment simultaneously affects and is a consequence of this activity and is thus intertwined with the survival of the species.
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