An ecosystem is a community of different species interacting with one another and with their non-living environment of matter and energy. Ecology focused on a right-hand portion of the spectrum .i.e levels of organizations from organ system to ecosystem. We study ecology from three points of view:
In this view, we study a description of different habitats.
We study how does earth works and how ecosystem does operate.
We study why natural selection favors this particular ecological solution.
So the basic problem of ecology is to determine the cause of distribution and abundance of organisms. Every organism lives in the matrix of space and time. Consequently, two ideas of distribution and abundance are of closely related. They may be seen quite distinct. What we observed for many species is that the numbers in an area vary in space.
Odum 1971, defines an ecosystem as any unit that includes all the organisms in the given area interacting with physical environment so that flow of energy leads to clearly define biotic structures and cycling of materials between living and non-living components.
The ecosystem comprises of living and non-living components. There is a cycling of inorganic substances like phosphorus, sulphur, carbon, nitrogen, hydrogen etc. inorganic chemicals such as protein, carbohydrates, lipids etc. between two components. Biotic component comprises autotrophic components and heterotrophic components. Autotrophic components accumulate light energy, use simple inorganic substances and build up of complex substances. These components are constituted mainly by green plants including photosynthetic bacteria. Heterotrophic components, also called consumers, in which utilization rearrangement and decomposition of complex materials predominate. There are two types of consumer i.e. macro consumers and micro consumers. Macro consumers are the consumers which are on order as they occur in a food chain are herbivores and carnivores. They are prototrophs which include chief animals that ingest organic matter. Micro consumers, popularly known as decomposers, are saprotrophs and include chiefly bacteria, actinomycetes and fungi. They break down the complex compounds of dead or living protoplasm, absorption of some of the decomposition or breakdown products and release inorganic nutrient in the environment making them available again to the autotrophs. Producers accumulate light energy and prepare food which is transferred to the primary consumers and then to the secondary consumers. After the death of this consumer, the energy remains as dead organic matter. The important nutrients locked in the biomass of plants and animals become incorporated into the soil and water through the action of decomposers called as mineralization process. The microbial activities of decomposers convert the minerals and other useful nutrients into the forms that can be readily taken up by plants and other producers. According to the law of conservation of energy, “Energy can neither be created nor be destroyed but can be transferred from one form to another.” The matter present in the soil is taken up by the producers and consumers take their food from producers. At that time, the matter present in the producers goes to the consumer and the process continues again and again.
In this way, we can explain that matter is not wasted but is transmitted from one organism or substance to other but doesn’t get destroyed. So in conclusion, we can say that there is no waste in a functional natural ecosystem.
It is not easy to compare terrestrial and aquatic systems because there is such a large variety of their environments. It is possible to recognize in the terrestrial part of the biosphere, a small number of units with distinctive vegetation and climate, each with a complex of communities of large extent. These units are known as biomes and six major biomes are usually recognized, namely the:
An aquatic ecosystem can be sub-divided into freshwater, estuarine and marine systems. These are differentiated on the basis of major chemical differences in water content. The terrestrial ecosystems consist of several major biomes such as forests, grasslands tundra, etc. These are determined largely by variations in climatic conditions between the poles and equator. These biomes can differentiate on the basis of their predominant types of vegetation such as grasses, shrubs or trees.
The productivity of an ecosystem or community is defined as the state at which radiant energy is stored by photosynthetic organisms in the form of organic substances.
Productivity is the accumulation of biomass (organic matter). The production rates differ ecosystem to ecosystem. For example; higher productivity in tropical rain forests and lowest in arctic and desert ecosystem. High rates of production, both in natural and cultured ecosystems occurs when physical factor are favorable and especially from outside the system that reduces the subsidies from outside the system that reduces the cost of maintenance. Such energy subsidies may take the form of wind and rain in a rain forest, tidal energy in an estuary or the fossils fuel, animal or human work energy used in the cultivation of crops. There are two types of productivity:
Primary productivity of an ecosystem, community or any part of there is defined as the rate at which radiant energy is stored by the photosynthetic or chemosynthetic activity of producer organisms in the form of organic substances which can be used as food materials.
Secondary productivity is the rate of storage at a consumer level. Since consumer only utilizes food materials already produced, with some respiratory loss and is converted to different tissues by an overall process, gross or net division is not appropriate. Energy flow from producer to herbivores (consumers) to omnivores and onward is termed as assimilation rather than production. At metabolic equilibrium, photosynthesis equals respiration and this is termed as compensation point.
E.p., Odum. Fundamentals of Ecology. USA: W.B Saunters Company, n.d.
Jr., Miller G.T. Living in the Environment. Belmont, California, USA: Wadsworth Publishing Company, 2003.