Ecosystem

An ecosystem is, therefore, defines as a natural functional ecological unit comprising of living organisms (biotic community) and their non-living (abiotic or physio chemical) environment that interact to form a stable self-supporting system. A pond, lake, desert, grassland, meadow, forest etc. are common examples of ecosystem.

Structure & Function of Ecosystem
(1) Abiotic Components
The non living factors or the physical environment prevailing in an ecosystem form the abiotic components. They have a strong influence on the structure, distribution, behavior and inter-relationship of organisms.

Abiotic components are two types
(a) Climatic Factors: Which includes rain, temperature, light, wind, humidity etc.
(b) Edaphic Factors: Which include soil, pH, torography mineral etc.

(2) Biotic Components
The living organisms including plants, animals and micro-organisms (Bacteria and Fungi) that are present in ecosystem form the biotic components.

On the basis of their role in the ecosystem the biotic components can be classified fied into three main groups:

(A) Producers: Photosynthesizing organisms

Producers are any kind of green plant. Green plants make their food by taking sunlight and using the energy to make sugar. The plant uses this sugar, also called glucose to make many things, such as wood, leaves, roots, and bark. Trees, such as they mighty Oak, and the grand American Beech, are examples of producers.

(B) Consumers

The animals lack chlorophyll and are unable to synthesis their own food. Therefore, they depend on the producers for their food. They are known as heterotrophs
(i.e. heteros = other, trophos = feeder)


The consumers are of four types

(a) Primary Consumers or First Order Consumer or Herbivores:
These are the animals which feed on plants or the producers. They re called herbivores. Examples are rabbit, deer, goat, cattle etc.




































(b) Secondary Consumers or Second Order Consumers or Primary Carnivores:
The animals which feed on the herbivores are called the primary carnivores. Examples are cats, foxes, snakes etc.

(c) Tertiary Consumers or Third Order Consumers:
These are the large carnivores which feed on the secondary consumers. Examples are Wolves.

(d) Quaternary Consumers or Fourth Order Consumers or Omnivores:
these are the largest carnivores which feed on the tertiary consumers and are not eaten up by any other animal. Examples are lions and tigers.

India as a Mega-Diversity Nation

India has a very rich diversity of wild plants and animals, and is considered to be one of the mega-diversity country. Its share of the global biodiversity is about 8.6% of wild plant animal species respectively. Estimates for the number of micro-organism species are not available. Parallel to this enormous diversity in domesticated animal such as buffalo, goat, sheep, pig, poultry, horse, ponies, camels, and yak. As per American standards, the productivity of these animals is very poor, but having undergone periods of rigorous selection, race are hardy, adaptable to heat and parasitic stresses and can survive o poor roughage. A great variety also exists among our crops. For example, Indian farmers probaly grew over 30,000 varieties of rice aloe.

Both plant and animal species are under threat of extinction primarily due to modification, degradation and loss of their habitats, causes by various developmental projects like industries, urban housing complexes, rail, road, and other communication networks, over exploitation, introduction of exotic species, pollution and global warming. Estimates show that about 50 species are being drawn to extinction every day, and at this rate about 25% of present day biodiversity is likely to become extinct during the next 20-30 years if appropriate are not taken for its conservation. It is therefore, the prime responsibility of all scientists and technocrats to ensure that developmental activities promoted by them cause no/ minimal loss to biodiversity of an area.

Deforestation

Deforestation is the permanent destruction of indigenous forests and woodlands. The term does not include the removal of industrial forests such as plantations of gums or pines. Deforestation has resulted in the reduction of indigenous forests to four-fifths of their pre-agricultural area. Indigenous forests now cover 21% of the earth's land surface. The World Resources Institute regards deforestation as one of the world's most pressing land-use problems.

The difference between forests and woodlands is that whereas in a forest the crowns of individual trees touch to form a single canopy, in a woodland, trees grow far apart, so that the canopy is open.

Of great concern is the rate at which deforestation is occurring. Currently, 12 million hectares of forests are cleared annually. Almost all of this deforestation occurs in the moist forests and open woodlands of the tropics. At this rate all Amazonia the Zaire basin, as well as a few protected areas within reserves and parks. Some countries such as Ivory Coast, Nigeria, Costa Rica, and Sri Lanka are likely to lose all their tropical forests by the year 2010 if no conservation steps are taken.

Cause of Deforestation
(1) Population Explosion
Population explosion poses a grave threat to the environment. Vast areas of forest land are cleared of trees to reclaim land for human settlement (factories, agriculture, housing roads, railway tracks etc.) growth of population increases the demand for forest products like timber, firewood, paper and other valuable products of industrial importance, all necessitating feeling of trees.

(2) Forest Fires
Fires in the forests may be due to natural calamities or human activities.
(a) Smoldering of human and organic matter forming a thick cover over the forest floor (i.e. ground fires).
(b) Dried twigs and leaves may catch fire (i.e. surface fires).
(c) In densely populated forests, tree tops may catch fire by heat produced by constant rubbing against each other (i.e. crown fires).
(d) Human activities like clearing forest for habitation, agriculture, firewood, construction of roads, railway tacks and carelessness (throwing burning cigarette stubbs on dried foliage).

Fire destroys fully grown trees, results in killing and scorching of the seeds, humans, ground flora and animal life.

(3) Grazing Animals
Trampling of the forest soil in the course of overgrazing by livestock has four reaching effects such as loss of porosity of soil, soil erosion and desertification of the previously fertile forest area.

(4) Pest Attack
Forest pests like insects etc. destroy trees by eating up the leaves, boring into shoots and by spreading diseases.

(5) Natural Forces
Floods, storms, snow, lightening etc. are thye natural forces which damage forests.

Effects of Deforestation
Forests are closely related with climatic changes, biological diversity, wild animals, crops, medicinal plants etc.
Large scale deforestation has many far-reaching consequences:

(a) Habitat destruction of wild animals (tree-using animals are deprived of food and shelter.)
(b) Increased soil erosion due to reduction of vegetational cover.
(c) Reduction in the oxygen liberated by plants through photosynthesis.
(d) Increase in pollution due to burning of wood and due to reduction in Carbon-dioxide fixation by plants.
(e) Decrease in availability of forest products.
(f) Loss of cultural diversity.
(g) Loss of Biodiversity.
(h) Scarcity of fuelwood and deterioration in economy and quality of life of people residing nera forests.
(i) Lowering of the water table due to more run-off and thereby increased use of the underground water increase the frequency of droughts.
(j) Rise in Carbon dioxide level has resulted in increased thermal level of earth which in turn results in melting of ice caps and glaciers and consequent flooding of coastal areas.

Food Web

Environment

Every organism is a specialized unit. It Invariably depends upon the environment and other organisms for its existence. It either eats other organisms or is eaten up by others and competes with others for the necessities of life such as food, shelter and mate.

Survival requires group association. such association and inter-relationships of organisms and environment in general constitute the Science of Ecology. The word was coined by Ernst Haeckel in 1869 and is derived from two Greek words "oikos" meaning 'house, habitation or place of living' and "logos" meaning 'study'. The field of ecology deals with the influence of environmental factors on all the aspects of life such morphology, physiology, growth, distribution, behaviour and survival of the organisms.

All the external conditions that affect the life of organisms i their natural habitats aggregate to form the environment i.e. 'the surroundings' of an organism.

The environment has been classified into :

(a) Physical or Abiotic Environment : It is composed of external physical factors like temperature, humidity, water, minerals and gases etc..

(b) Living or Biotic Environment : It is composed of all the living components-plants, animals and micro-organisms.

All these constituents of environment are referred to as the environmental factors or ecological factors or simply as factors. A factor is defines as an ecological condition which directly or indirectly affects the growth and development and hence the life of an organism.

"Environmental Studies" is the scientific of the environmental system and the status of its inherent or induced changes on organism. It includes not only the study of physical and biological characters of the environment but also the social and cultural factors and the impact of man on the environment

Objectives and Guiding Principles of Environmental Studies

According to UNESCO (1971), the objectives of environmental studies are:
(a) creating the awareness about environmental problems among people.
(b) imparting basic knowledge about the environment and its allied problems.
(c) developing an attitude of concern for the environment.
motivating public to participate in environment protection and environment improvement.

Case Study

Ozone Hole over Antarctica

There is so much of hue and cry over ozone hole which has got created over Antarctica. We can explain this phenomenon as follows:

In the stratospheric region , the chloro-fluoro-carbon (CFCs) got broken down by ultraviolet radiation of the sun and as such they release chlorine atom. This chlorine atom reacts with ozone and the subsequent product when its react with NO2, it forms chlorine nitrate. Since chlorine nitrate is an inert compound it cannot cause any harm to ozone. But in the case of Antarctica, a phenomenon of atmospheric circulation called polar vertex or circumpolar forms. This blocks the Warmer air from mixing with the air above the pole. The results is that the polar air gets trapped and it has no connection. with the outside warmer air. The results in cooling of air in the stratosphere. The temperature goes down upto - 90 degree C and ice crystals get formed which provide reaction surfaces for chlorine nitrate to react with water. This results in formation of HOCL and HNO3. This reaction continues to take place as long as circumpolar exists in winter season. But as the Antartic spring comes in August or September the HOCL forms CI and the hydroxyperoxye radical. This destroys the ozone. The cycle repeats itself creating a big ozone hole.

Hyderabad Water Supply and Sanitation Project

By 1989 Government of India had completed work on the Singur Dam in Andhra Pradesh. Te dam later became part of the World Bank supported Hyderabad Water Supply and Sanitation Project. The reservoir created by the dam provided much-needed irrigation water, electric power, and drinking water However, because of the dam construction, thousands of people had to relocate, and therefore, lost their livelihoods. The Hyderabad Water Supply and Sanitation Project extended its coverage to the resettlement and rehabilitation of people displaced by the rising water. The project helped relocate 3,600 households and identified 4,600 families that required assistance to re-establish their economic productivity.

A local non-governmental organization assisting with the economic rehabilitation helped determine the needs of villagers, and identified potential economic resources in each village. This resulted in the identification of a range of employment options. Entrepreneurs who had moved to the area were offered support in exchange for hiring villagers.

Project benefits were supplemented with ongoing district-level development resources. The district Administration helped integrate residents who had not been directly affected by the dam's construction. This inclusionary measure helped narrow the differences between those who did and did not receive benefits. When presented with a base grant (equivalent to a year's income) and a choice of options, many of the villagers, who were headers and weavers before resettlement, opted to use subsidized ban loans to invest in intensified agriculture, housing improvement, and better livestock development.

Deterioration of Taj Mahal

Mathuran Oil Refinery lies only 40 km away from Taj Mahal- one of the eight wonders of the world.

The Oil Refinery emits 25-30 tonnes of SO2 daily inspite of using low sulphur fuels. Air pollution sureys y Indian and International** firms have estimated that any increases in SO2 concentration above the present 1.75 kg/m3 wouls result in acidic precipiatation under condition of low wind speeds combined with humidity. This would results in the conservation of SO2 into sulphuric acid-which is the main cause of "Stone-Cancer".

The sulphuric acid could react with Calcium Carbonate (CaCO3) in the marle to form Calcium Sulphate (CaSO4)-which would cause pitting in the Taj.