Our Environment
NCERT Solutions
NCERT Exercise
1. 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
(c) and (d)
2. 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
(b) Grass, goat and human
3. 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
(d) All of the above
4. What will happen if we kill all the organisms in one trophic level?
It will create an imbalance in the ecosystem. Because each level is dependent on another level.
5. Will the impact of removing all the organisms in the trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
The removal of organisms at any level would upset the whole ecosystem as the food chain is disturbed. The survival of the higher level animals is completely dependent on the animals at the lower levels.
6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Biological magnification is the increase in concentration of harmful substances in the body of the living organism at each tropic level. The levels of biological magnification is different at different levels of the ecosystem.
7. What are the problems caused by the non-biodegradable wastes that we generate?
- Soil destruction
- Ecological imbalance
- Air pollution
- Water pollution
- Affects the soil fertility
- Reduces crop yield
8. If all the waste we generate is biodegradable, will this have no impact on the environment?
The degradation of large amount of biodegradable material requires a large number of decomposers. But large number of decomposers are not available. It will results in incomplete degradation. Due to this the number of files causing diseases increases.
9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
The ozone layer serves as a protective shield that blocks the dangerous ultra-violet rays. The ozone layer also keeps the planet’s temperature constant. If ultra violet reaches earth it causes various skin problems including skin cancer. CFCs (chlorofluorocarbons) used in air condition, refrigerators are chemicals that deplete the ozone layer. CFCs should be replaced with environmentally friendly replacements in refrigerants and fire extinguishers.
Intext Exercise
Pg. No. 260
1. What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.
Different levels in food chain where the transfer of energy or food takes place are known as trophic levels.
Ex: Grass → Grass hopper→ Lizard → Snake → Hawk
- Grass represents the first trophic level
- Grass hopper represents the second trophic level
- Lizard represents the third trophic level
- Snake represents the fourth trophic level
- Hawk represents the fifth trophic level
2. What is the role of decomposers in the ecosystem?
Decomposers helps in breaking down the complex organic compounds into simpler one by decomposing the dead plants and animals. Through this they help in recycling the nutrients. They act as a cleansing agent of the environment.
Pg. No. 262
1. Why are some substances biodegradable and some non-biodegradable?
Substances that a microorganisms like bacteria or decomposers like saprophytes can breakdown is known as biodegradable substance and those substances like plastics that cannot be breakdown by microorganisms/ decomposers are non-biodegradable substances.
2. Give any two ways in which biodegradable substance would affect the environment.
- They can create foul smell during decomposition process.
- It also produce some harmful gases that may contribute to global warming.
3. Give any two ways in which non-biodegradable substances would affect the environment.
- They cause air, soil and water pollution.
- They may cause bio-magnification in the food chain
Pg. No. 264
1. What is ozone and how does it affect the ecosystem?
The ozone layer is a region of Earth’s stratosphere. It absorbs most of the Sun’s ultraviolet radiation which is dangerous to human. So it act as protective shields.
2. How can you help in reducing the problem of waste disposal? Give any two methods.
- By using products that can be recycled.
- Separating biodegradable and non-biodegradable waste.
- Make biodegradable waste into compost.