Ecosystem

In general terms, an ecosystem can be defined as an ecological unit consisting of a biotic community (an assemblage of plant, animal and other living organisms in an area) together with its abiotic (non-living) environment (such as soil, precipitation, sunlight, temperature, slope of the land, etc.). The word ecosystem is an abbreviation of the term, "ecological system." A river, a swamp, a meadow, and a cave are all examples of ecosystems. Some consider the ecosystem to be the basic unit in ecology.

Humans are part of the environment and thus impact, and are impacted by, ecosystems. Forests provide wood for homes and an environment for recreation; wetlands purify our water; rivers provide fish and hydroelectric energy. Fifty percent of all jobs worldwide are tied to agriculture, foresty, and fishing. Human impacts often have caused dramatic changes to diverse ecosystems. Urbanization, industrial activities, agriculture, recreational activities, and foresty have impacted such things as biodiversity and numbers of organisms, modified biogeochemcial cycles, and increased pollution.

The twentieth century exhibited humanity's ingenuity in many ways, including a history of intervening in major river and wetland systems by creating dams for hydroelectic plants or navigation, or by divering water to open up wetlands for development. All large rviers in the temperate zone have been altered for human use, as have most of the world's large river floodplain ecosystems. It has been said that historically, if a forest, wetland or river was not producing jobs and wealth, it was cut drained, mined, or dammed. Clearly, the study of ecosystems and human impacts is important for creating a sustainable environment for future generations.

Size, scale and boundaries

The size and scale of an ecosystem can vary widely. They may be very large, such as a tropic rain forest, the Everglades, or the Pantanal, or very small, such as a test tube of phytoplankton or an aquarium tank with plants and fish. Some define a biome as an extensive ecosystem.

The boundary of an ecosystem are not always easy to delineate. Different ecosystems are often separated by geographical barriers, like deserts, mountains or oceans, or are isolated otherwise, like lakes or rivers. As these borders are never rigid, ecosystems tend to blend into each other. For example, the boundary of a river may seem clear, yet caimans crawl from the river to bask in the sun, herons get food from the river but nest in trees, and tapirs may swim in the water and yet live on the land. To some extent, the wholeearth can be seen as a single ecosystem, or a lake can be divided into several ecosystems, depending on the scale used.

Types of ecosystems

Ecosystems may be categorized in different manners. Following are some examples of how ecosystems may be labelled:

• Riverine ecosystem
  • River ecosystem
  • Sream ecosystem
  • Spring ecosystem
• Lacustrine ecosystem
• Pond ecosystem
  • Lake ecosystem
• Marine ecosystem
  • Costal water ecosystem
    • Estuary ecosystem
    • Lagoon ecosystem
  • Coral reef ecosystem
  • Soft-bottom continental shelf ecosystem
  • Upwelling continental shelf ecosystem
  • Open ocean ecosystem
  • Polar ocean ecosystem (the Artic and Antarctic oceans)
• Boundary ecosystem (where one body of water meets another (estuaries and lagoons), where a body of water meets land (wetlands), where one land area meets another land type.)
• Soil ecosystem
• Polar ecosystem (in polar regions, such as polar barrens and tundra)
• Mountain ecosystem (in mountainous areas)
• Agroecosystem (farms and livestock production systems
• Forest ecosystem
• Grassland ecosystem
• Urban ecosystesm (cities and subburbs)

Flow of energy

A major force llinking the abiotic and biotic constiuents of ecosystems is the flow of energy. The fundamental source of energy in almost all natural ecosystems is radiant energy from the sun. **** elaborate and mention that energy does not cycle

Nutrient cycles

Not what is and that it does cysle

History

The term ecosystem first appeared in a 1935 publication by the British ecologist Arthur Tansley (Tansley, 1935). However, the term had been coined already in 1930 by Tansley's colleague Roy Clapham, who was asked if he could think of a suitable word to denote the physical and biological components of an environment considered in relation to each other as a unit. Tansley expanded on the term in his later work, adding the ecotope concept to define the spatial context of ecosystems (Tansley, 1939). Modern usage of the term derives from the work of Raymond Lindeman in his classic study of a Minnesota lake (Lindeman, 1942). Lindeman's central concepts were that of functional organisation and ecological energy efficiency ratios. This approach is connected to ecological energetics and might also be thought of as environmental rationalism. It was subsequently applied by H.T.Odum, sometimes called the 'father' of ecosystems ecology, in founding the transdiscipline known as Systems Ecology.

Early conceptions of this unit were as a structured functional unit in equilibrium. This equilibrium was characterized by energy and matter flows between its constituent elements. Others considered this vision limited, and preferred to understand an ecosystem in terms of cybernetics. From this view an ecological system is not a structured functional unit in equilibrium, but a functional organisation at dynamic equilibrium, or what was also called steady state. This branch of ecology that gave rise to this view has become known as Systems Ecology. Steady state is understood as the phase of an ecological systems evolution when the organisms are "balanced" with each other and their environment. This balance is achieved through various types of interaction, such as predation, parasitism, mutualism, commensalism, competition, and amensalism. Introduction of new elements, whether abiotic or biotic, into an ecosystem tend to have a disruptive effect. In some cases, this can lead to ecological collapse and the death of many native species. The abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem. That is, how far the ecosystem is away from steady state.

Inter-species biological interactions in ecology

Amensalism • Commensalism • Mutualism • Neutralism • Synnecrosis • Predation (Carnivory, Herbivory, Parasitism, Parasitoidism, Cheating) • Symbiosis • Competition

References

ISBN links support NWE through referral fees

• Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology. Ecology 23: 399-418.
• Tansley, A. G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16: 284-307.

• Tansley, A.G. 1939. The British Islands and their Vegetation. Volume 1 of 2. University Press, Cambridge, Cambridge, United Kingdom. 484 pg.

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