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Basic Concept of Ecology

 The four basic concept of ecology are i. holism, ii. ecosystem, iii. succession and iv. conservation (R.Mishra , 1991).

                                                                  Holism 

The term holism (from a Greek word holon, meaning entity) was coined by the South African statesman, Jan Christian Smuts in his book Holism and Evolution in 1926 to explain the process of evolution by the coming together of lesser wholes in order to create the universe. Smuts defined holism as " the tendency in nature to form wholes that are greater than the sum of the parts through creative evolution." 

The hierarchical levels at which we discuss interacting units of ecology are, individual < population < community < ecosystem < biome < biosphere . Each unit is a whole built up by the interactions of lower level wholes into a higher level wholes in this kind of hierarchy. Williams Ophuls (1974) considered holism is the real base of ecology. It focused on system paradigm of interrelationships. 

Each ecological level and examples of the questions posed at each level and the approaches used to answer them are then described.

          A population is a group of individual organisms of the same species in a given area.  Population ecologists ask, "Why is this population of a particular density?" . Answers lie in the inherent biology of the species (constraints imposed by the levels of organisations below) and the ways in which members of the population interact with their environment. 

        A community is a group pf populations of different species in a given area. It may include all the populations in that area - all plants, all animals and microorganisms or may be defined more narrowly as a particular group such as the fern community or the seed-eating bird community of that area. A major concern of community ecologist is the question, " Why is the community of a particular diversity"? Diversity is a combination of the number of species and the number of individuals of each species in a community. another important question is, " Why does particular community occur at a given location?" Answer are sought in the influences of the abiotic environment, how communities interact and how communities change through time.  From evolutionary biology view point communities are much looser assemblages than are populations and thus answers to problems at community level must have be sought among the evolutionary histories of the constituent populations.

        An ecosystem is the whole biotic community in an given area plus its abiotic environment. Ecosystem ecology emphasises the movements of energy and nutrients ( chemical elements) among the biotic and abiotic components of ecosystems. A major concern is , "How much and what rates are energy and nutrients being stored and transferred between components of a given ecosystem?" The biotic components of any ecosystem are linked as food chains. Food chains are interlinked to form complex food webs. Food webs are the basic units of ecosystem  ecology. Thus ecology begins with populations and  culminates in ecosystems . Energy flows through ecosystem, being acquired from outside as light energy from the sun and being intimately lost from the ecosystem as heat dissipated by the respiration of all community members. Nutrients are cycled within ecosystems to a much greater extent.

Fig. Pattern of energy and nutrient exchange in a hypothetical ecosystem.


       Clements and Shelford (1939), put forth a concept of biome. According to their view, under similar climatic conditions, there many simultaneously develop more than one communities, some reaching to climax stage, others under different stages of succession. This complex of several communities in any area, represented by an assemblage of different kinds of plants, animals etc., sharing a common climate, is called a biome. 

      The earth's living organisms interacting with their physical environment may be considered as a giant , vast ecosystem, which is the largest and most nearly self-sufficient biological system we know, and this is designated as the biosphere or ecosphere. Thus the planet earth along with the atmosphere (air, land, water) that sustain life is known as biosphere.

Location: Kolkata, West Bengal, India

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