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Structure of an Ecosystem |
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Structure of an Ecosystem
An ecosystem is the basic functional unit in ecology, as it includes both organisms and their abiotic environment. No organism can exist without the environment. Ecosystem represents the highest level of ecological integration which is energy based. A pond, a lake, a coral reef, part of any field and a laboratory culture can be some of the examples of ecosystems. Thus an ecosystem is defined as a specific unit of all the organisms occupying a given area which interacts with the physical environment producing distinct trophic structure, biotic diversity and material cycling. The term ecosystem was first proposed by the British ecologist A.G. Tansley.
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Most of earth’s surface is oceanic, and the deepest part of these oceans is deeper than the highest peaks of the mountains. The marine environment is extensive and complex, containing a vast array of communities and is divided into two major provinces-estuaries and deep ocean. Oceans are the ultimate sinks for all water soluble minerals, and are saline. Apart from these, mangroves also form part of the marine ecosystem which is a rich source of biotic and abiotic elements.
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There are two basic processes in an ecosystem. One of the processes involves a cycle of exchange of materials between living things and the environment. The plants synthesis complex organic materials from the raw materials. The organic matter ultimately releases the raw material which are returned to the environment. This mechanism is called cycling of materials. The other basic requirement of an ecosystem is the constant input of energy. The ultimate source of energy is the sun whose solar energy is captured by green plants. Other organisms derive their nutrition and energy from the plants. The energy taken by these organisms is passed on to other organisms.
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In this way energy is transferred from one organism to another. This is called
flow of energy.
The major aspects of an ecosystem are its structure and function. Structure
involves:
1. composition of biological community including species, numbers, biomass, life history and distribution in space, etc.
2. quantity and distribution of non-living materials, such as nutrients, water, etc.
3. range, or gradient of conditions of existence, such as temperature, light, etc.
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Functions of an ecosystem involves:
1. rates of biological energy flow, i.e. the production and respiration rates of the community.
2. rates of materials or nutrient cycles.
3. biological or ecological regulation including both regulation of organisms by environment and regulation of environment by the organisms. Thus in any ecosystem, structure and function are studied together.
Odum (1959) classified the abiotic components of an ecosystem into three
parts:
i. inorganic nutrients like C, N, H, etc.
ii. organic compounds constituting the organism.
iii. climatic factors
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The term abiotic means without life or nonliving. Many substances such as water, oxygen, sodium chloride, nitrogen and carbon dioxide are abiotic when they are physically outside living organisms, such as in air or water, but once within living organisms they become part of the biotic world. Many elements may be tightly bound in inorganic compounds as silicon in sandstone or aluminum in feldspar, and are unavailable to living organisms, Elements such as oxygen which are normally very active in biological processes may be in an abiotic form readily available to living organisms such as free O2, CO2, etc., or they may be in an inaccessible form as silicon dioxide in quartz, a major component of granite. One of the most important aspects of an ecosystem is the rate of release of nutrients from solids, as this regulates the rate of function of the entire system.
The abiotic components can be classified into three groups:
1. Climatic regime-includes temperature, light and other physical factors which
directly influence the organisms in a given area.
2. Nutrients (material cycling)-includes inorganic substances (C, CO2, H2O, H2, P, etc.) and organic substances
3. Energy circuits-includes grazing circuits and organic detritus circuits.
The amount of abiotic materials present in any ecosystem is called standing state.
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