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Chapter-y, Ecology and Environment, 5.1: Concept of Environment:, The life containing and life supporting environment of the world is restricted to., very irregular layer (5 to 20 km thick) around the globe. This thin veil of living material, on the earth is called ecosphere or biosphere. Thus, the biosphere is that part of earth in, which life exists. Biosphere may be divided into parabiosphere and eubiosphere. The, parabiosphere is that part of biosphere where environmental conditions are not entirelv, hospitable and this includes such broad areas as higher altitude, the polar regions, the, deepest ocean troughs, the most extreme deserts and certain localised regions as, volcanoes, geysers and heavily polluted areas of land and water. The remaining portion, (the eubiosphere) is composed of three chief media-air, water and earth or land and, accordingly it has been divided into three subdivisions :, i), ii), Atmosphere, Hydrosphere, Lithosphere or pedosphere, iii), In ecology the study of reciprocal relationship between an organism or a group of, organisms and its environment. The environment literally means the surrounding. The, environment is the aggregate of all those things and set of conditions which directly or, indirectly influence not only the development or growth and quality of life of individual, organisms but also the communities at a particular place. It is comprised of a number of, factors which interact with one another and also influence the responses of the organisms., Any external force, substance or condition affecting the organisms in any way is referred, to as environmental factor. Soil, moisture, wind and temperature are, thus, factors and, the environment., The natural place where organisms or communities of organisms live is called, habitat. The habitat implies a particular set of environmental factors in a given locality, and is, therefore, generally used in a more concrete sense than the environment, as for, example, water is the habitat of aquatic organisms and land is a habitat for numerous, terrestrial organisms. Aquatic habitat comprises three major categories namely, fresh, water habitat, marine habitat and brackish habitat. Biosphere can be divided into many, major categories of land masses called biomes. Biomes are distinct large areas of earti, with relatively homogenous climate and flora and fauna, as for example, deserts, foresis,, prairies etc. Biomes are subdivided into small units, each with its own particular set, of, physical conditions. These small units are called Zones. For example, a forest biome Can, Botany Semester V / 128, Scanned by CamScanner

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te divided into ground zone and canopy zone and desert biome can be divided into, arface and subterranean zones. The ocean can be regarded as single biome (the marine, biome) which can be divided into surface, abyssal and intertidal or littoral zones., It, Within each biome there may be numerous habitats, each characterized by a, particular set of conditions and well adapted community of organisms. Within a, particular habitat an individual is generally confined to restricted situation which is called, ecological niche., a, al, The environmental or the habitat factors influence the characters and composition, of individual plants and plant communities. Any feature of an organism or, enables the organism to exist under conditions of its habitat is called an adaptation. An, organism accumulates many adaptive features in it. Such features may ensure a degree of, success either by allowing the plant to make full use of the amounts of nutrient, water,, heat and light available to it or by providing a significant amount of protection against, some unfavorable or adverse factors, such as very high or very low temperature, drought,, and parasitism and so on. The adaptive features of organism may be hereditary, they may, be genetically controlled) or they may be induced by the habitat factors., In, le, its, part which, y, ne, Is, d, In an ecosystem the species and its environment are taken as a complex "whole"., Environment, as pointed out earlier, in itself is a complex of factors acting, reacting and, interacting with the organism complex. Thus, the organisms and their environment are, wedded together and are in state of constant flux. Relationship between organisms and, their environment are based on certain principles which are summarized as follows:, Everything influencing the life processes of an organism constitutes its, of, or, al, of, environment., Environment in a habitat may be considered into, biotic and abiotic components and the activities of the organisms are influenced, by the combined effects of various environmental factors., 5., An organism is a component of the environment and the materials and energy, required for the maintenance of the body and sustenance of life of organisms, constitute the abiotic environment., Life is the energy exchange process between the organism and environment and, death means cessation of the exchange process., An organism cannot exist in vacuum., The environment requirements of different organisms differ from individual to, individual and also with age and need., Life activities are influenced by that environmental component which occurs in, minimum quantity., of, Botany Semester V/ 129, Scanned by CamScanner

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Life activities of an organism are influenced by the minimum or maximum, quantity of the environmental components or factors, as for example, nutrients, light, temperature, moisture., An organism may show different tolerance limit for a particular environmental, factor in different habitats and at different age and stage of life history., The biotic and abiotic components of the environment are in constant flux in any, habitat which induce ecological succession with the passage of time and change, in the environment., Sun is the only source of energy in our earth's environment and the life depends, on solar energy., Energy is neither created nor destroyed. It can be transformed from one form to, the other., Energy flow from the sun to the plants, to the other organisms and then to the, space is always unidirectional., Energy and space relationships of the organisms cause niche differentiation, within the habitat which brings about ecological stability in the community life., Life on the earth exists in a thin mantle or layer around the earth. This layer, forms the biosphere., • The biosphere is not uniform structure and it consists of several life supporting ., habitats called ecosystems., An ecosystem has producers (plants), consumers (animals), and decomposers, constituting the biotic component, and life supporting matter and energy which, constitute the abiotic component., Concept and scope of ecology:, A. Concept of ecology, The two components of nature, organisms and their environment are not only, much complex and dynamic but also interdependent, mutually reactive and interrelated., Ecology, relatively a new science, deals with the various principles which govern such, relationships between organisms and their environment., The term ecology was coined by combining two Greek words, oikos (meaning', house' or' dwelling place') and logos (meaning the study of) to note such relationships, between the organisms and their environment. Thus, ecology is the study of organisms'at, home'. There is some controversy out the author who coined the term ecology and first, used it in the literature. Kormondy tried to give credit for the first use of the term, ecology., American ecologist Frederick Clements considered ecology to be "the science of, the community," Woodbury treated ecology as "a science which investigates organisms, Botany Semester V / 130, Scanned by CamScanner

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e relation to their environment, and a philosophy in which the world of life is interpreted, in terms of natural processes." Taylor defined ecology as "the science of all the relations, f all organisms to all their environments." However, the recent development in study of, ecology has been the recognition of the fact that the biotic (living) and abiotic (non-, living) components of nature are not only interrelated but both these components function, in an orderly manner as a definite system, thus structure and function should be studied, together for fuller understanding of this nature., In Haeckel's definition of ecology, he refers to the "surrounding outer world",, which we now call the environment of an organism. His "organic and inorganic, conditions", Biotic factors are the other organisms encountered, whether of the same or, different species. Abiotic factors are the physical and chemical conditions such as, temperature, moisture, respiratory gases and substrate., Odum with such an approach put forth a new definition of ecology, and in his, own words "As you know ecology is often defined as the study of interrelationships, between organisms and environment"., Like other sciences ecology too has its own principles and basic concepts-, 1. All living organisms and their environment are mutually reactive, affecting each, other in various ways. Animal population, flora, and vegetation are, interdependent through the environment and are mutually reactive., 2. The dynamic environment and organisms make ways for the development of, different kinds of organisms through a process known as succession. The process, continues till the development of a community which is now more or less stable, and is now able to keep itself adjusted in equilibrium with the environment. This, final stage of community is called a climax. When both, biotic and abiotic, components are considered, the basic structural and functional units of nature are, 3. The radiant energy is trapped by the autotrophic organisms (producers) and is, transferred as organic molecules to the heterotrophic organisms (consumers)., This energy flow is uni-directional or non-cyclic., 4. The chemical components of the ecosystem move in defined cycles, biogeochemical cycles. Within the ecosphere, biological systems frequently, regulate the rate of movement of cycling of the chemicals. Role of water as the, universal solvent for biological systems is much relevant here., ecosystems., B. Scope of Ecology :, Ecology is the science that needs minimum time and labor for its introduction to, Botany Semester V/131, Scanned by CamScanner