Fundamental Concepts and Principles of Ecology!
There are certain basic fundamental ecological principles which describe various aspects of living organisms e.g. evolution and distribution of plants and animals, extinction of species consumption and transfer of energy in different components of biological communities, cycling and recycling of organic and inorganic substances, interactions and inter-relationships among the organisms and between organisms and physical environment etc.
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Some important fundamental concepts and principles of ecology in terms of eco-system may be outlined as follows:
1. Eco-system is a fundamental well structured and organised unit that brings physical environment and living organisms together in a single framework which facilitates the study of interactions between biotic and abiotic components. Ecosystems are also functional units where in two biotic components, namely autotrophic and heterotrophic components are of major significance.
2. The biotic and abiotic components of biosphere ecosystem are intimately related through a series of large scale cyclic mechanisms which help in the transfer of energy, water, chemicals and sediments in various components of the biosphere.
3. Sustained life on the earth is a characteristic of eco-system, not of individual organisms or population (D.B. Botkin and E. A. Keller 1982).
4. In 1974, M. J. Holliman suggested four environmental principles to describe holistic nature of natural environment which largely influence the biological communities in a biosphere eco-system.
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The different principles are as follows:
(i) Nothing actually disappears when we throw it away because all the materials are rearranged and cycled and recycled through a series of cyclic pathways in the natural environment.
(ii) All systems and problems are ultimately if not intimately, inter-related. It does not make squabble over which crisis is most urgent. We cannot afford the luxury of solving problems one by one that is both obsolete and ecologically unsound anyway.
(iii) We live on a planet earth whose resources are finite.
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(iv) Nature has spent literally millions of years refining a stable eco-system.
5. According to D. B. Botkin and E.A. Keller (1982) the physical and biological processes follow the principle of uniformitarianism. This principle states that same physical (right from the origin of the planet, earth and its atmosphere) and biological (since the origin of first organism) processes which operate today, operated in the past not necessarily with constant magnitude and frequency with time and will operate in future but at rates that will vary as the environment influenced by human activity.
6. Natural hazards affect adversely the biological communities in general and man in particular when biological processes are associated with natural hazards, yet severe hazards are created.
7. All living organisms and physical environment are mutually reactive. The varying degrees of interactions among organisms, at both inter and intraspecific levels are positive, negative and sometimes neutral.
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8. Solar radiation is the main driving force of the eco-system and it is trapped by green plants through the process of photo-synthesis. Energy flow in eco-system is unidirectional and non-cyclic. Eco-system energy flow (energetics) helps eco-system. The energy pattern and energy flow are governed by the laws of thermodynamics.
9. The energy is transferred from one trophic level to the next higher trophic level but organisms at higher trophic levels receive energy from more than one trophic level.
10. R. L. Linderuan (1942) suggested some principles about the relationships between the trophic levels within a natural ecosystem.
(i) Principle-1:
With an increase in distance between the organisms of a given trophic level and the initial source of energy, the probability of the organisms to depend exclusively on the preceding trophic level for energy decreases.
(ii) Principle-2:
The relative loss of energy due to respiration is progressively greater to higher trophic levels because the species at higher trophic levels being relatively larger in size have to move and work for getting food and therefore more energy is lost due to respiration.
(iii) Principle-3:
Species at progressively higher trophic levels appear to be progressively more efficient in using their available food supply, because increased activity by predators increases their chances of encountering suitable prey species, and in general predators are less specific than their prey in food preference.
(iv) Principle-4:
Higher trophic levels tend to be less discrete than the lower ones because the organisms at progressively higher trophic levels receive energy from more than one source and are generalists in their feeding habit and they are more efficient in using their available food.
(v) Principle-5:
Food-chains tend to be reasonably short. Four vertical links is a common maximum because loss of energy is progressively higher for higher trophic levels and species at higher levels tend to be less discrete.
11. The inorganic and organic substances are circulated among the various components of biosphere through a series of closed system of cycles collectively known as bio- geochemical cycles.
12. The eco-system productivity depends on two factors:
(i) The availability of the amount of solar radiation to the primary producers at trophic level-I.
(ii) The efficiency of the plants to convert solar energy into chemical energy.
There is marked positive correlation between primary productivity and solar radiation.
13. There is inbuilt self-regulating mechanism in natural ecosystem, known as homeostatic mechanisms, through which any change caused by external factors in the eco-system is counter balanced by the responses of the system to the change in such a way that ultimately eco-system or ecological stability is restored. The ecological diversity and complexity enhance ecological or eco-system stability.
The ecological stability can be attained by the following manners:
(i) According to C. S. Elton (1958), increase in the diversity of food webs promotes ecosystem stability.
(ii) According to P.H. MacArthur (1955), the ecosystem stability increases with increase of number of links in the food web.
(iii) According to E.P. Odum (1971), high species diversity of a mature ecosystem representing a climax community is related to more stability of natural eco-system.
14. Eco-system instability results when an eco-system becomes unable to adjust with environmental changes.
15. According to Charles Darwin (1859), evolution of species epitomises the inherently dynamic nature of ecosystem.
16. Darwin’s concept of progressive evolution of species was subsequently challenged by Devries and a new concept of mutation was proposed. Mutation is a process of spontaneous evolutionary change which introduces inheritable variations in species.
T. Dobzhansky (1950) suggested the following ideas regarding mutation:
(i) The mutation process furnishes the raw materials for evolution.
(ii) During sexual reproduction, numerous gene patterns are produced.
(iii) The possessors of some gene patterns have greater fitness than the possessors of other patterns in available environment.
(iv) The frequency of superior gene patterns is increased by the process of natural selection while the inferior gene patterns are suppressed.
(v) Groups of some combinations of proven adaptive worth become segregated into closed genetic system, called species.
17. The transition stages of sequential changes from one vegetation community to another vegetation community are called ‘sere’. The sere is complete when the succession of vegetation community after passing through different phases, culminates into equilibrium condition. The vegetation community developed at the end of succession is called ‘Climax vegetation’, ‘Climax community’ or ‘Climax climax.’
18. Besides community succession, the eco-system also undergoes the process of successional changes. There are two fundamental ideas regarding the process of successional changes.
(i) According to E.P. Odum (1962), ecological succession is one of the most important processes which results from the community modifying the environment, (ii) According to R. H. Whittaker (1953), the successional development of ecosystem is characterised by four major changes in the ecosystem viz.
(a) Progressive increase in the complexity and diversity of community;
(b) Progressive increase in the structure and productivity of the eco-system;
(c) Increase in soil maturity;
(d) Increase in relative stability and regularity of populations within the eco-system and stability of the eco-system itself.
19. The eco-system is mainly modified by man through the exploitation of natural resources. Man reduces ecological diversity and complexity by removing a host of biotic communications.
20. Preserving diversity in a world of rapidly shrinking resources will require a prompt and universal response on an appropriate application of ecological knowledge.