Our Environment

• Environment means everything which surrounds us. It may include living(biotic) and non-living (abiotic) components. So, it may includes besides all creatures, water and air also.

• Environment affect the life and development of an organism in its natural habitat and vice a versa.

• Substances that are decomposed are called bio-degradable. Eg. organic wastes while some substances like plastics, some chemicals (DDTs and fertilizers) are inert and can’t be decomposed, are called Non-biodegradable.

• Actually non-biodegradable persist in the environment for a long time or may harm the various members of the eco-system.

Eco System And Its Component

• All the interacting organisms in an area together with non living components form an ecosystem. So an ecosystem consists of both biotic (living creatures) and abiotic components like temperature, rainfall, wind, soil etc.

• All living organisms are classified on the basis of the manner in which they survive in the Ecosystem. These groups include.

I) Producers – All green plants, blue green algae can produce their food (Sugar and starch) from in organic substance using light energy (Photosynthesis).

II) Consumers – Include organisms which depend on the producers either directly or indirectly for their sustenance. In other word consumers consume the food produced by producers.

III) Decomposers – Fungi and Bacterias which break down (decompose) the dead plant, animals complex compounds into the simpler one. Thus decomposers help in the replenishment of the natural resources.

• Food chain refers to an arrangement of different biotic groups in a sequence of enery transfer. These biotic groups are producer herbivores, carnivores. For Eg. T1(Grass)-T2(DearA)-T3(Lion)

• In a food chain, these biotic components where transfer of energy takes place is called a trophic level.

• The green plants capture 1% of sunlight falls on their leaves.

• The flow of energy is unidirectional in a food chain.

• There is gradual decrease in the amount of energy transfer from one trophic level to next trophic level in a food chain.

• While the conc. of harmful chemical increases with every next trophic level in a food chain. It is called Bio-magnification For Eg. Grass(10 ppm)DDT – Dear(200 ppm)DDT-Lion(5000 ppm)DDT.

• Maximum concentration of such chemicals accumulated in human bodies.

• Naturally the food chains are inter-connected with each other forming a web like pattern, which is known as FOOD WEB.

• The loss of energy at each step (trophic level) is very high, so very little amount of energy remains after four trophic levels.

• There are gnerally a big population at lower trophic levels of an ecosystem. For Eg. the population of the producer is higher than the consumer carnivore (lion) population.

Environmental Problems

• Changes in environment affect us and our activities change the environment around us. This led to the slow degreadation of environment that arose many environmental problems. Eg. depletion of the Ozone Layer and waste
disposal.

Depletion of Ozone Layer

• Ozone (O ) layer is largely found in the stratosphere which is a part of our 3 atmosphere from 12 km – 50 km above sea level.

• Ozone is a deadly poison at the ground level.

• Ozone is formed as a result of a following photo chemical reaction.

• Ozone layer is a protective blanket around earth which absorbs most of the harmful U.V. (Ultraviolet) radiation of the Sun, thus protecting the living beings of the earth from health hazards like skin cancer, cataract in eyes,
weaken immune system, destruction of plants etc.

• The decline of Ozone layer thickness is Antarctica was first discovered in 1985 and was termed as OZONE HOLE.

Reason of Ozone Depletion

• Excessive use of CFCs (Chloro Flouro Carbon) a synthetic, inert chemical Eg. Freon which are used as refrigerants and in fire extinguishers, caused Ozone depletion in the upper atmosphere. A single chlorine atom can destroys 1,00,000 Ozone molecules. U.N.E.P. (United Nation Environment Programme) did an excellent job in forging an agreement to freeze CFC production at 1986 levels (KYOTO Protocol) by all countries.

• Garbage Disposal – Industrialization and rise in demand of consumer goods have created a major problem in the form of wastes/garbage accumulation and its disposal especially in urban area.

• The different methods of solid wastes disposal commonly used around the world are.

1. Open dumping : A conventional method in which solid wastes dumped in selected areas of a town. It actually cause pollution.

2. Land fillings : Wastes are dumped in low living area and are compacted by rolling with bulldozers.

3. Composting : Organic wastes are filled into a compost pit (2m x 1m x 1m). It is then covered with a thin layer of soil. After about three months the same garbage filled inside the pit changes into organic manure.

4. Recycling : The solid wastes is broken down into its constituent simpler materials. These materials are then used to make new items. Even non-bio degradable solid wastes like plastic, metal can be recycled.

5. Reuse : A very simple conventional technique of using an item again and again. For Eg. paper can be reused for making envelops etc.

Important Question

1.Mention one negative effect of our affluent life style on the environment.

Ans. Our activity in our affluent life style pollute the environment.

2. Why has there been huge hue and cry against the use of CFC’s ?

Ans. CFC’s on reaching the upper layer of atmosphere causes ozone layer depletion and allows UV rays to enter earth’s atmosphere.

3. Name the radiations from the sun that are absorbed by ozone layer. Mention one harmful effect caused by them.

Ans. Ultraviolet radiations are absorbed by ozone layer. Ultravoilet radiations cause skin cancer.

4. What is meant by non-biodegradable waste ? Identify biodegradable waste from the following :

Empty packet of chips, empty bottle of mineral water, empty paper box of sweets, empty tin of a cold drink.

Ans. Substances that do not breakdown by biological process are called non-biodegradable waste. Empty paper box of sweets is biodegradable.

5. State two methods to get rid of non-biodegradable wastes.

Ans. We should carry cloth bags when we go for shopping. Non-biodegradable waste should be collected separately and sent for recycling.

6. Why is ozone layer getting depleted at the higher levels of the atmosphere?

Ans. Depletion of ozone layer is due to the use of chlorofluorocarbons which are used as refrigerants and in fire extinguishers.

7. State the function of digestive enzymes.

Ans. Digestive enzymes break down the food into small and water soluble soluble molecules.

8. Where do plants get each of the raw materials required for photosynthesis ?

Ans. Plants get carbon dioxide from the atmosphere and nitrogen from the soil for photosynthesis.

9. What is meant by the term Environment ?

Ans. Environment is the sum total of all external conditions and influences that affect the life and development of an organism. Environment includes all the physical or abiotic and biological or biotic factors.

10. Name any two non-biodegradable wastes.

Ans. DDT and polythene bags.

11. In a certain study conducted on occurrence of DDT along food chains in an ecosystem, the concentration of DDT in grass was found to be 0.5 ppm in sleep it was 2 ppm and in man it was 10 ppm. Why was the concentration of DDT maximum in case of man ?

Ans. DDT is non-biodegradable. It accumulates at each tropic level. As man is positioned at the highest tropic level, there is maximum accumulation of DDT in man. This phenomenon is called biological magnification.

12. Explain how does making of kulhads affect our environment ?

Ans. A lot of soil is needed for making kulhads. It results in large scale pepletion of top fertile soil. Moreover, disposal of used kulhads is not so easy.

13. Define a food web. State its significance for ecosystem.

Ans. A system of food chains which are interconnected between various organisms is called a food web. The significance of food wen is in the maintenance of ecological balance based upon interdependence of different organisms.

14. State one important function of ozone layer in the atmosphere. How is it formed there ? Which compounds are responsible for the depletion of ozone layer ? How do these compounds enter into the atmosphere ?

Ans. Ozone layer prevents harmful ultraviolet radiations to reach earth’s atmosphere. Ozone is formed at the higher level of atmosphere by the action of UV radiations on O2 molecule. HIgh energy UV radiations split apart some oxygen to form ozone molecules as shown by the following equations :

O2 —— O + O

O2  +  O —– O3

Chlorofluorocarbons are responsible for the depletion of ozone layer. These compounds which are used in refrigerators and fire extinguishers get leaked during manufacture or repair and go up high into the atmosphere.

15. (a)What is an ecosystem ? List its two main components.

(b) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain

Ans.(a) A self-sustaining functional unit consisting of living and non-living components is called ecosystem.

Components : Biotic components like plants and animals. Non-biotic components like soil, wind, light etc.

(b) A pond is a complete, natural and self-sustaining ecosystem whereas an aquarium is an artificial and incomplete ecosystem, therefore it needs regular cleaning for proper running.

16. “Damage to the ozone layer is a cause of concern” Justify this statement. Suggest any two steps to limit this damage.

Ans. Ozone layer protects the earth from the harmful effects of ultraviolet radiations. Damage to ozone layer will result in UV rays reaching the earth and cause skin cancer, cataract and damage to immune system.

Steps to limit the damage :

(i) Minimise the use of CFC.

(ii) Freeze CFC production at 1986 level as per UNEP recommendation.

(iii) Device chemicals in place of CFC’s to perform their functions.

17. Why are bacteria and fungi called decomposers ? List any two advantages of decomposers ?

Ans. Bacteria and fungi are called decomposers because they degrade and decomposes dead remains of plants and animals into simpler inorganic susbtance which go into the soil as nutrients.

Advantages : Decomposers degrade garbage and organic wastes which would otherwise cause environment problem. It prevents foul smell and checks spread of diseases.

Decomposers recycle the nutrients through biogeochemical cycle.

18. What is ten percent law ?

Ans. Energy available at each successive trophic level of food chain is ten percent of that at the previous level.