"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 15
OUR ENVIRONMENT
BASIC CONCEPTS
1) Environment is define as sum total of all conditions and influences that affect the development and life of organisms.
2) The interplay of material cycles and energy flows in natural eco-systems is self sustaining and self correcting. However, this equilibrium is sensitive to external stimuli such as human activities promoted by socio-economic goals. Increasing demands and aspirations of human society create a rising demand for goods and services. Thus human impose changes on natural eco-systems and this creates conflicts between human goals and natural processes.
3) Pollution is an undesirable change in the physical, chemical or biological characteristics or air, water and soil that may harmfully affect the life or create a potential hazard for any living organism. Pollutants are substances which cause pollution.
4) Biodegradable pollutants are those pollutants which can be decomposed by microbes (microorganisms) with the help of various enzymes over a period of time. The biodegradable substances becomes pollutants when that are present in large quantities and are not degraded at right time due to any reason. Non-biodegradable substances are those which microbes, present in nature, are not able to breakdown into simpler forms.
5) Eco-system :- The living world needs inputs of energy and matter. These are exchanged between living and non-living components. Thus, living organism (both plants and animals) and physical components (such as soil, temperature, water, sunlight, etc.) of an area together from a functional unit. This functional unit comprising living and non-living components from a functional system known as eco-system. In short, Eco-system is the whole biotic community (living organisms) in a given area plus its abiotic environment (physical factors like temperature, rainfall, wind, soil and minerals). Eco-system can be as large as a forest, or small as a pond or lake. This functional system may be natural as forest or may be artificial (man-made),e.g., a crop field or an aquarium.
6) Biome :- A major eco-system which includes all the eco-systems present in a geographical area is called biome.
7) Biosphere :- It is the largest unit of organisation of life. It includes all the biomes of the world i.e., terrestrial, aquatic or aerial where the life exists. It is supported by lithosphere, up to 5 km below sea level ; hydrosphere, the bodies of water on, inside and near the surface of the earth; and atmosphere, up to 7-8 kms in the air above sea level. Biosphere is a single large self-sustaining biological system.
8) Biotic components of an eco-system are linked as food chains. Food chain are interlinked to form complex food webs. In any eco-system, various living organisms are arranged in a definite sequence according to their food habits. Plants are producers which are eaten by herbivores, which in turn are eaten by carnivores. This transfer of food energy from the source in plants through a series of organism with repeated eating and being eaten is known as a food chain in an eco-system. Under natural conditions in the same eco-system there generally operate a number of linear food chains at a time. These chains are interlinked with each other at several points. This interlocking pattern of a number of food chains forms a web-like arrangement which is called a food web.
10) Trophic level :- Each step or level of the food chain forms a trophic level. The producers are at the first trophic level who fix up the solar energy and make it available for heterotrophs or consumers. Herbivores come at the second level, small carnivores at third level and large carnivores at fourth level as depicted in the figure.
11) Decomposers are microorganisms comprising of bacteria and fungi that breakdown the dead remains and waste products of organisms. They breakdown the complex organic substances into simple inorganic substances that go into the soil and are used up once again by the plants.
- Green plants in a terrestrial eco-system capture about 1% of the sun energy that falls on the leaves and convert it into food energy.
- An average of 10% of the food eaten by the primary consumers is turned into its own body and is available for the next level of the consumers.
- 10% can be taken as average value for the amount of organic matter that is present at each step and reaches the next tropic level.
14) Ozone layer :- There is layer of ozone gas in the stratosphere (a part of atmosphere). Ozone at higher levels of the atmosphere is a product of UV radiation acting on oxygen molecule. The higher energy UV radiations split apart some molecular O₂ into free oxygen 'O' atoms. These atoms then combine with O₂ to form O₃ as depicted below :-
O + O₂ → O₃
Ozone layer protects us from Sun's harmful UV radiations by cutting them off. There is increased concern about the effect of ozone depletion. The depletion of ozone causes the harmful UV rays to reach the earth and this has resulted in increased incidence of skin cancers in humans. UV rays may also cause genetic mutations in living organisms. Major air pollutants responsible for the depletion of ozone layer are chlorofluorocarbons (CFCs), nitrogen oxides and hydrocarbons. CFC is used in air cleaning solvents, aerosol propellants, in foam insulation and in certain fire extinguishers.
15) Solid Waste (Garbage) includes glass bottles, crockery, plastic containers, polythene and other packing materials, automobile spares, machines, cycle parts, construction wastes, sludge, dead animal skeletons, crop residues, etc. These pile up at public places and cause obstruction in daily life. To solve the problem of solid wastes technologies have been developed to recycle most of the solid waste items such as paper cans, newspapers, metallic vehicles parts. To control solid waste pollution methods like
- recycling,
- burning of waste and utilising heat to warm residential units/generate electricity,
- composing of organic waste for preparation of manure and bio-gas are suggested.
