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Ecology
From Wikipedia, the free encyclopedia
For other uses, see Ecology (disambiguation). Ecology | | | | Ecology addresses the full scale of life, from tiny bacteria to processes that span the entire planet. Ecologists study many diverse andcomplex relations among species, such aspredation and pollination. The diversity of life is organized into different habitats, from terrestrial(middle) to aquatic ecosystems. |
Ecology (from Greek: οἶκος, "house"; -λογία, "study of"[A]) is the scientificstudy of interactions among organisms and their environment, such as the interactions organisms have with each other and with their abiotic environment. Topics of interest to ecologists include the diversity, distribution, amount (biomass), number (population) of organisms, as well as competition between them within and among ecosystems. Ecosystems are composed of dynamically interacting parts including organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such asprimary production, pedogenesis, nutrient cycling, and various niche construction activities, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits, and the variety of organisms is called biodiversity. Biodiversity, which refers to the varieties of species, genes, and ecosystems, enhances certain ecosystem services.
Ecology is an interdisciplinary field that includes biology and Earth science. The word "ecology" ("Ökologie") was coined in 1866 by the German scientistErnst Haeckel (1834–1919). Ancient Greek philosophers such as Hippocratesand Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology transformed into a more rigorous science in the late 19th century. Evolutionary concepts on adaptation and natural selection became cornerstones of modern ecological theory. Ecology is not synonymous with environment, environmentalism, natural history, or environmental science. It is closely related to evolutionary biology, genetics, and ethology. An understanding of how biodiversity affects ecological function is an important focus area in ecological studies. Ecologists seek to explain: * Life processes, interactions and adaptations * The movement of materials and energy through living communities * The successional development of ecosystems, and * The abundance and distribution of organisms and biodiversity in the context of the environment.
Ecology is a human science as well. There are many practical applications of ecology in conservation biology, wetland management, natural resource management (agroecology, agriculture, forestry, agroforestry, fisheries), city planning (urban ecology), community health, economics, basic and applied science, and human social interaction (human ecology). Organisms and resources compose ecosystems which, in turn, maintain biophysical feedback mechanisms that moderate processes acting on living (biotic) and nonliving (abiotic) components of the planet. Ecosystems sustain life-supporting functions and produce natural capital like biomass production (food, fuel, fiber and medicine), the regulation of climate, global biogeochemical cycles, water filtration, soil formation, erosion control, flood protection and many other natural features of scientific, historical, economic, or intrinsic value.

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Integrative levels, scope, and scale of organization[edit]
See also: Integrative level

Ecosystems regenerate after a disturbance such as fire, formingmosaics of different age groups structured across a landscape. Pictured are different seral stages in forested ecosystems starting from pioneers colonizing a disturbed site and maturing in successional stages leading to old-growth forests.
The scope of ecology contains a wide array of interacting levels of organization spanning micro-level (e.g., cells) to planetary scale (e.g., biosphere)phenomena. Ecosystems, for example, contain abiotic resources and interacting life forms (i.e., individual organisms that aggregate into populations which aggregate into distinct ecological communities). Ecosystems are dynamic, they do not always follow a linear successional path, but they are always changing, sometimes rapidly and sometimes so slowly that it can take thousands of years for ecological processes to bring about certain successional stages of a forest. An ecosystem's area can vary greatly, from tiny to vast. A single tree is of little consequence to the classification of a forest ecosystem, but critically relevant to organisms living in and on it.[1] Several generations of an aphid population can exist over the lifespan of a single leaf. Each of those aphids, in turn, support diverse bacterial communities.[2] The nature of connections in ecological communities cannot be explained by knowing the details of each species in isolation, because the emergent pattern is neither revealed nor predicted until the ecosystem is studied as an integrated whole.[3] Some ecological principles, however, do exhibit collective properties where the sum of the components explain the properties of the whole, such as birth rates of a population being equal to the sum of individual births over a designated time frame.[4]

Hierarchical ecology[edit]
See also: Biological organisation and Biological classification
System behaviors must first be arrayed into different levels of organization. Behaviors corresponding to higher levels occur at slow rates. Conversely, lower organizational levels exhibit rapid rates. For example, individual tree leaves respond rapidly to momentary changes in light intensity, CO2 concentration, and the like. The growth of the tree responds more slowly and integrates these short-term changes.
O'Neill et al. (1986)[5]:76
The scale of ecological dynamics can operate like a closed system, such as aphids migrating on a single tree, while at the same time remain open with regard to broader scale influences, such as atmosphere or climate. Hence, ecologists classify ecosystemshierarchically by analyzing data collected from finer scale units, such as vegetation associations, climate, and soil types, and integrate this information to identify emergent patterns of uniform organization and processes that operate on local to regional,landscape, and chronological scales.
To structure the study of ecology into a conceptually manageable framework, the biological world is organized into a nested hierarchy, ranging in scale from genes, tocells, to tissues, to organs, to organisms, to species, to populations, to communities, toecosystems, to biomes, and up to the level of the biosphere.[6] This framework forms apanarchy[7] and exhibits non-linear behaviors; this means that "effect and cause are disproportionate, so that small changes to critical variables, such as the number ofnitrogen fixers, can lead to disproportionate, perhaps irreversible, changes in the system properties."[8]:14