We have Provided the NCERT/CBSE Solutions chapter-wise for Class 10 Science Chapter 15 Our Environment with Answers by expert subject teacher for latest syllabus and examination. Students can take a free NCERT Solutions of Our Environment. Each question has right answer Solved by Expert Teacher.
CBSE Solutions Class 10 Science Our Environment
Page No. 257
Questions
Q1. Why are some substances biodegradable and some non-biodegradable?
Answer: Some substances are biodegradable because the enzymes released by the micro-organism helps in breaking down the biodegradable wastes but some are non-biodegradable because they can not be broken down by the micro-organism.
Q2. Give any two ways in which biodegradable substances would affect the environment.
Answer:
- Stink: Within a day or so waste biodegradable substances begin to stink and produce foul gases.
- Pests and Pathogens: The decaying biodegradable substances become breeding places of flies and many other pests. They also contain a number of pathogens. Flies and other pests carry the germs to all the places visited by them resulting in spread of diseases.
Q3. Give any two ways in which non-biodegradable substances would affect the environment.
Answer: Non-biodegradable substances affect the environment by:
- They contaminate soil and water resources as they cannot be decomposed by micro-organisms.
- These substances, when accidentally eaten by stray animals, can harm them and can even cause their death.
Page No. 261
Questions
Q1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer: In the food chain, the transfer of food or energy takes place at various levels and these levels are known as trophic levels. Example:Grass → Goat → Man
In the food chain,
- Grass represents the first trophic level
- The goat represents the second trophic level
- Man represents the third trophic level
Q2. What is the role of decomposers in the ecosystem?
Answer: Various role played by decomposers in the ecosystem are:
- They clean the environment.
- They decompose biodegradable substances into useful substances.
- They release nutrients into soil by decomposing dead and decaying matter, thus making the soil fertile.
- They maintain the nutrient pool by returning back the nutrients in the pool.
Page No. 264
Questions
Q1. What is ozone and how does it affect any ecosystem?
Answer: Ozone (O2) is a molecular gas formed by three atoms of oxygen. While O2, which we normally refer to as oxygen, is essential for all aerobic forms of life, ozone is a deadly poison. However at the higher levels of the atmosphere, ozone performs an essential functions, it shields the surface of the earth from ultraviolet radiation from the sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.
Is stratosphere ozone form a layer, known as ozone layer which protect us from harmful ‘UV’ rays of Sun. But due to some holes in the ozone layer ‘UV’ rays are reaching on earth and increasing its temperature. The increase in temperature of earth is causing global warming. So ozone can affect all ecosystems on earth.
Q2. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer: Waste disposal is becoming the biggest problem of all local bodies. It is consuming a big chunk of their revenues. Even then the points of collection are turning into stinking areas. Transport of waste to disposal site is seldom perfect. There is stink all the way. A lot of waste is thrown on the roads by the vehicles carrying the waste.
The quantity of waste can be reduced if you form the habit of separation of waste into biodegradable and non-biodegradable parts.
- Non-biodegradable Waste. Most often the non-biodegradable waste is recycled. It is taken away by rag pickers.
- Biodegradable Waste. Biodegradable waste is putressible. It can be composted or vermicomposted to prepare compost for your kitchen gardens. The technique can also be used in schools and other institutions. Some institutes in big cities have installed incinerators for disposal of combustible components of waste. Hospital waste is being compulsorily incinerated to reduce contamination and spread of diseases.
Page No. 264
Exercise
Q1. Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer: (c) and (d) both
Q2. Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer: (b) Grass, goat and human
Q3. Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer: (d) All of the above
Q4. What will happen if we kill all the organisms in one trophic level?
Answer: The various lins or steps representing organisms in a food chain at which the transfer of food and energy takes place are called trophic’ levels. For examples, plants constitute the first trophic level and the herbivores consumer plants e.g, deer or cow they constitute second trophic level. Lion consume deer.
So lion consitute third trophic lelve. If we kill all the organisms of the one trophic level then food or energy cannot be transferred to the next trophic level and the organisms of this trophic level and all organisms of next to this trophic level will suffer for survival.
Q5. 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?
Answer: Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, on removing producers; herbivores would not be able to survive or they would migrate and ecosystem would collapse. If herbivores are removed, producers would grow unchecked and carnivores would not get food. If carnivores are removed, herbivores would increase to unsustainable levels and could destroy the producers.
If decomposers are removed, the dead animals would pile up due to which the environment would become polluted. In addition to this, if dead animals will not decompose, the recycling of nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the balance of the ecosystem the presence of organisms is necessary at each trophic level.
Q6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer: Biomagnification: The phenomenon that involves progressive accumulation of non-biodegradable chemicals at each trophic level is called bio-magnification or bio-accumulation. The maximum concentration of non-biodegradable chemicals gets accumulated in the body of human beings.
The level of biological magnification would not be same at each level. It will go on increasing as . we move to higher trophic levels.
Q7. What are the problems caused by the non-biodegradable wastes that we generate?
Answer: Following are the problems caused by the non-biodegradable wastes:
- These substances cannot be decomposed by the microorganisms.
- As the quantity increases, dumping becomes a problem.
- Non-biodegradable wastes like heavy metals may enter the food chain in the upper trophic levels.
- They may escape to the groundwater which causes soil infertility and disturbance in pH of the soil.
Q8. If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer: If all the waste generated would be biodegradable this will also create problem. As the numbers of decomposers will be quite low so wastes cannot be broken down into harmless simpler substance at right time. It will became breeding ground for flies causing spread of diseases. It will also emits foul smell which makes the life of people miserable.
Q9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer: The ozone layer is the protective layer of the earth from harmful rays. It plays a significant role in protecting all living and nonliving organisms. If a layer is broken no organism will survive. Following measures, the steps being taken to limit this harm.
- We must always minimize the employment of vehicles.
- We must always not encourage the burning of fossil fuels.
- It’s currently necessary for all the producing firms to form CFC- free refrigerators throughout the globe.
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