CHAPTER
15
OUR ENVIRONMENT
1. Write the aquatic organisms in order of who cats whom and make a food chain
2. Write the source of oxygen and Co to the aquatic organisms.
3. Give two examples of biodegradable waste
4. Give two example of non bio degradable waste
5. What is depletion of Ozone layer? What is its cause?
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Answers
Answer:
5. Ozone is a molecule of oxygen with 3 atoms its formula is O3. The ultra violet radiations split oxygen into free oxygen atoms, these atoms combine with oxygen molecules to form ozone.
Ozone Ecosystem:
At ground level ozone is poisonous but at higher level it is very useful as it protects all living organisms from harmful UV radiations of the sun. It doesn�t allow , the ultra violet radiations to enter the surface of earth. The UV radiations cause ionizing effect that leads,� to skin cancer in human beings.
1. If all the organisms in one trophic level are killed then all the organisms of next trophic level which are dependent on these are killed. Next trophic levels will no!get food to eat and the entire food chain gets disturbed. At the same time thei�organisms at the lower trophic level will reproduce and the population will increase in abundance there by , disturbing the ecosystem.
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Ans. The impact of removing all the organisms in a trophic level will be same. If the organisms of any trophic level be removed it will certainly damage the ecosystem.
For example,
Grass → Grass hopper Frog → Snake → Peacock
In this if all grasshoppers are killed/removed frogs will strive and grass will reproduce in abundance.
If snakes are removed then the number of frogs will increase which will disturb the entire ecosystems
Ans. The pesticides and chemicals are absorbed by plant from the soil and enter the food chain. Being non-biodegradable they accumulate progressively at, each trophic level. As human occupy the top level of any food chain, the maximum concentration of chemicals is found in our bodies. This is called biological magnification.
The level of magnification will be different at different trophic levels, the maximum concentrations will be at the highest trophic level and the chemical will be less at lower trophic levels.
3. (i) As the non-biodegradable waste cannot be broken down into simpler forms hence they keep on accumulating ins nature causing pollution.
(ii) They cause diseases.
(iii) It also causes biological magnification.
If all the waste we generate is bio-degradable and is managed in such a way that it is allowed to decompose then it will have no impact on the environment.
Ozone layer in the strastosphere is very helpful in shielding harmful UV rays. In absence of ozone layer heavy damage to organism may occur. It may cause diseases like skin cancer, cataract, reduced crop production etc.
The damage is limited bye UNEP (United Nations Environment Programme), it has forged an agreement to freeze for CFC production in 1986.
CFC– Chlorofluorocarbons used as refrigerants and in fire extinguishers.