Environment and different ecosystem and its structure, function, Ecosystems-Concepts-Productivity, Biosphere-Components and characteristics

          According to ISO definition environment is the surroundings in which an organization operates including air, water, land and natural resources, flora, fauna, humans and their interrelations. The environment is the sum total of all living and non-living factors which directly or indirectly influences the growth and development of the organisams

            The word environment is derived from the French word “environ”. The meaning of the French word is somewhat related to “encompass”  “encircle” etc. It is believed to have been introduced into the subject by biologist Jacob Van Erkul  In the early 1900s.

Here the components are classified in terms of biotic and abiotic based upon life. The biotic components are further listed as producers, consumers and decomposers and the abiotic components are classified as climatic (water, air) and edaphic (land). It is from this component system that the study of structure of ecosystem was evolved.

Ecosystem structure and function

Ecosystem structure        

All ecosystems have to include both abiotic and biotic components, the interactions, and a known source of energy. The simplest but least representative of ecosystems therefore contains just one living plant – the biotic component, in a small terrarium with light exposure to which water source with essential nutrients for the plant’s growth has been added – the abiotic environment.       

At a core functional level, ecosystems normally contain producers able to harvest energy from sunlight by photosynthesis and to use the energy to turn carbon dioxide with other inorganic chemicals in the organic building blocks of life. The consumers feed upon this captured energy, while decomposers not only feed on the energy, but also break up the organic matter into the inorganic constituents, for them to be used again by the producers. Those interactions among the producers and organisms which consume and decompose are called trophic interactions, composed of trophic levels in the energy pyramid, and the most energy and mass are in the primary producers, at the base, while the higher levels of the pyramid, beginning with the primary consumers that feed on producers, the secondary consumers which feed on these, and so forth. Trophic interactions are described in a more detailed form as the food chain, which organizes the specific organisms by the trophic distance from the primary producers, and with food webs, which map the feeding interactions between all the organisms in the ecosystem.

Ecosystem function

By definition, all ecosystems cycle matter and use energy, and the processes define the fundamental ecosystem functions as well. Energetic processes in an ecosystem are normally described by speaking of trophic levels that define the position of organisms according to their level of feeding in comparison to the original energy taken in by primary producers. Always the energy doesn’t cycle and ecosystems need a continuous inflow of high-quality energy in order to maintain their function and structure. For this reason, ecosystems are "open systems" needing a net inflow of energy to continue over time.

Biosphere-Components and Characteristics

Biosphere is area of the earth inhabited by life. It contains all the earth's ecosystems. 
This is a thin layer of oceans, lakes, and streams. The land to the depth of a few meters and the atmosphere to an altitude of a few kilometers. The biosphere is postulated to have evolved 3.5 billion years ago.  In a general sense, biospheres are any closed, self-regulating systems containing ecosystems.

1. Water (oceans, lakes, rivers, streams). All life is water based. Organisms use it to live in and use it to keep hydrated on land. It keeps the earth's temperature from getting too hot or too cold. 

2. Land is the solid foundation for plants, fungi, animals to interact with each other. 

3. Atmosphere is used to hold the oxygen needed for aerobic life to exist. It is the main mover of our weather and controls the climates around the world

 

Ecosystem concepts

·                  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.

·                  Environment which is actually a complex of several interrelated factors and is much dynamic (i.e varying with time and space), works as sieve selecting organism for growth from so many forms, as its one or the other factor becomes critical at critical stages of the life cycle of the species.

·                  The species puts each effort to maintain its uniformity in structure, function, reproduction, growth and development by preservation of its genetic pool. However, species is also plastic and reacts to varying environment to get itself adjusted structurally and physically in the changed environment, may arise by virtue of somatic plasticity, the ecads, or by the reorganization of their genes during sexual reproduction, the eco types. Thus species may increase their capacity of tolerance towards changing environment by the developing ecads and ecotypes.

·                  It is not only the environment which influences the life of organisms, but organisms too modify their environment as a result of their growth, dispersal, reproduction, death, decay etc., Thus, the environment is caused to change due to organism’s activities. 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 the community called climax.

·                  Clements and Shelford (1939) however put forth a concept of biome wherein all plants and animals are related to each other by their coaction and reaction on the environment. According to this view, under similar climatic conditions, there may simultaneously develop more than one communities, some reaching to climax stage other under different stages of succession. This complex of several communities in an area represented by an assemblage of different kinds of plants, animals etc., sharing a common climate called biome.  In the above account, basic concepts of ecology has been has been explained mainly upon structural basis. However, with the introduction of ecosystem concept in ecology, functional aspects along with the structural ones are to be strongly emphasized. Tansely (1935) thus emphasized the role of environment, with its various factors interacting with each other in his comprehensive term ecosystem which involves all the non-living and living factors working in a complex. With the new concept in ecology, following are the basic concepts:   

·                  When both, biotic and abiotic components are considered, the basic structural and functional units of nature are ecosystem. Discrete biological units consists of population and communities, including biomes. Each population occupies a specific niche, a unique functional position with respect to other organisms with which it interacts.

·                  There exists varying degree of +, - or even neutral interactions among the organisms, both at inter and intra specific levels, which determine along with abiotic parameters, the degree of success a particular population has given within a given habitat. Population ecologists study interaction at population as well as community levels. They study competition, usually between population from the same trophic level (such as herbivorous competing  for same grass i.e population ecology involving individuals of same species), and prey-predator interactions between members of adjacent trophic levels (i.e population ecology involving interactions between individuals of different species, at community level).

·                  Also, there are involved energetic of ecosystem, as energy is the driving force of this system. The radiant energy is trapped by the auto trophic organisms (producers) and is transferred as organic molecules to the heterotrophic organisms (Consumers). This energy flow is unidirectional or non cyclic. The primary producer efficiency is measured by (NPP/Total consumed)x 100. Secondary production efficiency is measured by (NSP/Total consumed)x 100    

·                  Energy efficiency is lost at successive trophic level.                         

·                  The entire array of organisms inhabiting a particular ecosystem is called a community. In a typical ecosystem, plants and other photosynthetic organisms are the producers that provide the food. Ecosystems can be permanent or temporary. Ecosystems usually form a number of food webs. Ecosystems are functional units consisting of living things in a given area, non-living chemical and physical factors of their environment, linked together through nutrient cycle and energy flow

·                  The chemical components of the ecosystem move in a defined cycles –biogeochemical cycles. Within the ecosphere, biological systems frequently regulate the rate of movement of cycling of the chemicals. Role of water as universal solvent for biological system is much relevant here.

·                   Successful growth of the organisms is governed by limiting factors. For success in growth and reproduction with a particular, an organism requires various essential factors from its environment. The success of an organism is limited not only by the deficiencies in substances or condition but also by the excesses. The minimal and maximum levels of tolerance for all ecological factors of species vary seasonally, geographically and according to the age of the population.

·                  Under natural conditions, different kinds of population undergo succession. Ecosystem undergo an orderly process of change with time, passing from a less complex to more state. This process involves not only changes in species composition but also changes in the physical environment of a community. The terminal or stabilized state is known as the climax. According to Evans (1956), the ecosystem involves the circulation, transformation and accumulation of energy and matter through the medium of living things and their activities. Thus, dynamic abiotic components of the environment and assemblage of plants and animals there, as a result of interactions between themselves keep modifying and changing each other, and this leads to the development of ecosystem

·                  Then come the possibilities of disruption and exploitation of ecosphere. As a result of natural condition or activities of man, species diversity of an ecosystem is reduced. It leads to a setback to the state of development and reduction in the stability of the ecosystem. Mans exploitation of ecosystem is directed toward channeling productivity to his needs. Applied ecology or human ecology is the use of ecological concepts to describe human activities and determination of ways in which people can best obtain their needs from ecosystems. Ecosystem are simultaneously altered by human activities are called managed, whereas those free from such disturbance are referred to as natural.