This important chapter from NCERT Solutions for Class 10 Science Chapter 13, Our Environment explores the delicate balance of our natural world and how human activities impact the ecosystems we depend upon. From understanding how energy flows through food chains to learning about the breakdown of waste materials and the growing problem of environmental pollution, this chapter highlights the crucial role we play in protecting our planet for future generations. This chapter is part of the comprehensive NCERT Solutions Class 1o Science series, which covers all chapters in detail.
The chapter covers ecosystem components, food chains and webs, the role of decomposers, ozone layer depletion, waste management, and the concept of biodegradable and non-biodegradable substances. Every solution has been designed keeping CBSE board exam patterns in mind, with clear diagrams, practical examples, and comprehensive explanations that ensure students develop both environmental awareness and problem-solving confidence for their examinations.
NCERT Solutions for Class 10 Science Chapter 13 - All Exercise Questions
Q.
Which of the following groups contain only biodegradable items?
1. Grass flower and leather
2. Grass, wood and plastic
3. Fruit-peels, cake and lime juice
4. Cake, wood and grass
Q.
Which of the following constitute a food chain?
1. Grass, wheat and mango
2. Grass, goat and human
3. Goat, cow and elephant
4. Grass, fish and goat
Q.
Which of the following are environment friendly practices?
1. Carrying cloth bags to put purchases in while shopping
2. Switching off unnecessary lights and fans
3. Walking to school instead of getting your mother to drop you on her scooter
4. All of the above
Q.
What will happen if we kill all the organism in one trophic level?
Q.
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 ecosystem?
Q.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Q.
What are the problems caused by the non-biodegradable wastes that we generate?
Q.
If all the waste we generate is biodegradable, will this have no impact on the environment?
Q.
Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage?
Class 10 Chapter 13 Science Questions & Answers – Our Environment
Q1.Which of the following groups contain only biodegradable items?
- Grass flower and leather
- Grass, wood and plastic
- Fruit-peels, cake and lime juice
- Cake, wood and grass
Solution: c) Fruit-peels, cake and lime juice and d)cake, wood and grass
Q2. Which of the following constitute a food chain?
- Grass, wheat and mango
- Grass, goat and human
- Goat, cow and elephant
- Grass, fish and goat
Solution: b) Grass, goat and human
Q3. Which of the following are environment friendly practices?
- Carrying cloth bags to put purchases in while shopping
- Switching off unnecessary lights and fans
- Walking to school instead of getting your mother to drop you on her scooter
- All of the above
Solution: d) All of the above
Q4.What will happen if we kill all the organism in one trophic level?
Solution: Death of all the organisms of one trophic level would affect the organisms of the previous trophic level and the next trophic level. If all the organisms of one trophic level are killed then the number of organisms of the next trophic level would decrease as they feed on the organisms of the trophic level. The number of organisms of the previous trophic level would increase because the organisms that feed on them are killed.
For example in the food chain consisting of, Grass ---> Goat ---> Lion, if all the goats are killed then the number of lions would decrease due to lack of food and grass population would increase due to under grazing.
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?
Solution: Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. If the organisms of first trophic level i.e., producers are removed, then the entire food chain will be disturbed and finally all the organisms might die. If the organisms of the topmost trophic level are removed then a disturbance in the ecosystem would occur as there would arose a competition in the organisms of the second topmost trophic level for food and space due to their overproduction in the absence of the organisms of the topmost trophic level.
Removal of organisms of any trophic level would definitely create a disturbance in the ecosystem. Hence, in an ecosystem, organisms of any trophic level cannot be removed.
Q6.What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Solution: Biological magnification is a phenomenon of accumulation or increase in the concentration of some toxic substance in the bodies of organisms of each trophic level.
Pesticides like DDT etc are generally sprayed on plants to eradicate pests. These pesticides are then washed down into soil and water bodies. Plants absorb these substances with water whereas aquatic animals such as fishes take up these substances from the water body. On eating these plants and aquatic animals, these toxic substances enter our body.
Yes, the magnification is different at different trophic levels of the ecosystem. The animals at the higher trophic levels will receive more of these toxic substances along with their food than animals at the lower trophic level. Thus, at each tropic level the magnification will be high as compared to the previous trophic level.
Q7.What are the problems caused by the non-biodegradable wastes that we generate?
Solution: The waste that is not degraded in the nature is called non-biodegradable waste. The non-biodegradable wastes cause the following problems:
- They increase soil and water pollution.
- Non-biodegradable waste like polyethene bags blocks the drains.
- Disposal of these non-biodegradable waste releases poisonous gases that pollute the air also
Q8.If all the waste we generate is biodegradable, will this have no impact on the environment?
Solution: Though the biodegradable waste do not stay for long in the environment but their excess pose various threats to the environment. Accumulated biodegradable waste like kitchen waste serves as a breeding ground for various flies, mosquitoes, microorganisms etc that may cause various diseases and epidemics in their surroundings.
Q9.Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage?
Solution: Hole in ozone layer will allow ultraviolet rays to reach the earth’s surface. These ultraviolet (UV) rays are harmful for living organisms in the following ways:
- These rays may cause skin disease, such as skin cancer.
- These rays cause retarded growth and destruction of pigments in plants.
- UV rays may disturb the ecological balance by killing the microorganisms, decomposers and other useful microbes
Following steps should be taken to prevent damage of ozone layer:
- According to Montreal Protocol (1989) the compounds like chlorofluorocarbons which cause depletion or hole in ozone layer should be used judiciously
- Use of chemical pesticides should be minimised
- Use of public transport should be encouraged
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NCERT Solutions for Class 10 Science Chapter 13 – FAQs
Q1. What is the difference between biodegradable and non-biodegradable substances?
Biodegradable substances are materials that can be broken down into simpler, harmless substances by biological processes involving microorganisms like bacteria and fungi. Examples include food waste, paper, wood, cotton cloth, and vegetable peels. These substances decompose naturally and return nutrients to the soil. Non-biodegradable substances are materials that cannot be broken down by biological processes and persist in the environment for long periods, causing pollution. Examples include plastics, glass, metals, synthetic fibers, and polythene bags. These substances accumulate in the environment and can harm living organisms through bioaccumulation in food chains.
Q2. What are trophic levels and why is energy transfer limited to 3-4 levels in a food chain?
Trophic levels represent the position of organisms in a food chain based on their feeding relationships. The first trophic level consists of producers (plants), the second level has primary consumers (herbivores), the third has secondary consumers (small carnivores), and the fourth has tertiary consumers (top carnivores). Energy transfer is limited to 3-4 trophic levels because only about 10% of energy is transferred from one level to the next, following the 10% law. The remaining 90% is lost as heat during metabolic processes, movement, and other life activities. After 3-4 transfers, insufficient energy remains to support another trophic level, making longer food chains unsustainable.
Q3. What is ozone layer depletion and how does it affect life on Earth?
The ozone layer is a protective blanket of ozone (O₃) gas in the Earth's stratosphere that absorbs harmful ultraviolet (UV) radiation from the sun. Ozone depletion refers to the thinning of this layer, primarily caused by chemicals like chlorofluorocarbons (CFCs) used in refrigerators, air conditioners, and aerosol sprays. When released, these chemicals break down ozone molecules, creating "holes" in the ozone layer. This allows more UV radiation to reach Earth's surface, which can cause skin cancer, cataracts, weakened immune systems in humans, reduced crop yields, and harm to aquatic ecosystems. International efforts like the Montreal Protocol have helped phase out CFCs to protect the ozone layer.