Environment: Science Class 10 Chapter 15 questions, answers

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In Science Class 10 Chapter 15: Environment (NCERT, NBSE, SEBA, TBSE etc.), you will learn the environment that surrounds us and gain knowledge about ecosystems, the critical function they serve in preserving the balance of the planet as well as study the ideas of food chains and food webs, which show how interdependence among all living things is necessary for survival. The chapter will also cover the detrimental effects that human activity, such as ozone depletion and improper waste management, can have on the environment. Knowing about these problems will enable you to protect the environment and lead a more sustainable life. Get here the questions, answers, textbook solutions, PDF, MCQs of this chapter.

children recycling, illustrating class 10 science chapter 15

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1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

Answer: Trophic levels refer to various links or steps in a food chain where the transfer of food and energy occurs.

Eg. Sun → Grass → Grasshopper → Shrew → Owl

In this case, grass is the producer, and the grasshopper serves as the main consumer. Then the shrew, a secondary consumer, consumes the grasshopper, and the owl, a third consumer, consumes the shrew.

2. What is the role of decomposers in the ecosystem?

Answer: In the ecosystem, decomposers play the following role: 

(i) They clean the environment.
(ii) They break down biodegradable materials into useful ones.
(iii) They make the soil fertile by decomposing dead and decaying matter, which releases nutrients into the soil.
(iv) They replenish the nutrients in the pool to keep it healthy.

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1. Why are some substances biodegradable and non-biodegradable?

Answer: All the substances are classified as biodegradable and non-biodegradable as some substances can be decomposed by microorganisms and others cannot. Substances that are broken down into simple soluble forms are called biodegradable substances, and the substances that are not decomposed by microorganisms into harmless substances are called nonbiodegradable substances.

2. Give any two ways in which biodegradable substances would affect the environment.

Answer: The environment would also be affected by the biodegradable materials:

(i) They might emit an unpleasant odour as they decompose.
(ii) They might release toxic gases like ammonia, methane, and carbon dioxide.

3. Give any two ways in which non-biodegradable substances would affect the environment.

Answer: The following ways that non-biodegradable materials can harm the environment:

(i) Biomagnification is brought on by substances like DDT and BHC that enter the food chain.
(ii) They contribute to pollution.
(iii) They also eliminate beneficial microorganisms.

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1. What is ozone, and how does it affect any ecosystem?

Answer: Three oxygen atoms combine to form the triatomic molecule known as ozone (OO3). As it protects (OO3) from the atmosphere, ozone creates a layer on the surface of the earth. ultraviolet The radiation from the sun is absolutely necessary for this planet to exist. These radiations are extremely dangerous and can lead to skin cancer and cataracts in people. Additionally, it harms the crops.

2. How can you help reduce the problem of waste disposal? Give any two methods.

Answer: To reduce waste disposal, the following actions should be taken: 

(i) Sorting biodegradable from non-biodegradable materials.
(ii) By minimising their use, repurposing them, and recycling them.


1. Which of the following groups contains 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:(A), (C) and (D)

2. Which of the following constitutes a food-chain?

Answer: (B) Grass, goat, and human

3. Which of the following are environmentally-friendly practises?

Answer: (D) All of the above

4. What will happen if we kill all the organisms at one trophic level?

Answer: Any trophic level’s loss of an organism will have an effect on the other trophic levels, either directly or indirectly. The ecosystem will become unbalanced as a result. Consider the food chain below, which has three trophic levels:

Grass ⟶ Deer⟶ Tiger

The “producers” in this instance, which are grasses, occupy the first trophic level. Deer serve as the “primary consumer” on the second trophic level. The “secondary consumer,” a tiger, resides in the third trophic level.

Case I: If every producer perishes (Producer missing) The absence of grass will cause deer to starve to death. Due to the lack of deer, all tigers will perish if they cannot find food (deer).

Case II: If the key clients are absent The populations of producers and carnivores will both be impacted if the herbivore goes extinct. The tiger population will decline as deer, which is their food source, becomes scarcer. Since deer won’t eat it, the population of producers or grass will increase (herbivore).

Case III: If there are no secondary consumers Without tigers, the number of deer or other major consumers will rise quickly, which will lead to a decline in the number of grass or producer animals.

5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can organisms of any trophic level be removed without causing any damage to the ecosystem?

Answer: It is true that depending on the trophic level, the effect of removing the organisms varies. For instance, the population of consumers would be at risk if all producers were eliminated. However, eliminating all primary consumers has a positive impact on the population of producers and a negative impact on the population of secondary consumers. The ecosystem becomes unbalanced when all of a trophic level’s organisms are eliminated. As a result, it is impossible to remove trophic level organisms without harming the ecosystem.

6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer: The process of increasing the concentration of some toxic, nonbiodegradable substances, such as pesticides, in trophic levels of a food chain is known as “biomagnification” or “biomagnification.” These toxins end up building up in the top trophic level as a result. Pesticides have the potential to enter various food chains and ultimately our bodies. As the top trophic level, humans accumulate the highest concentration of these chemicals in their bodies. Thus, at various trophic levels, the degree of biological magnification varies. From one trophic level to the next in the food chain, the concentration of pesticides rises. At the highest trophic level, the pesticide is concentrated to its fullest extent.

7. What are the problems caused by the non-biodegradable wastes that we generate?

Answer: Waste that is not biodegradable cannot be broken down by biological agents like microorganisms. They harm the environment in the following ways: 

a. They continue to exist and pollute the environment.
b. If consumed, they can cause harm or even death to organisms.
c. They ingest food and lead to biomagnification.

8. ‘Energy flow in a food chain is unidirectional’. Justify this statement. Explain how the pesticides enter the food chain and subsequently get into our body.

Answer: In food chains, energy moves in a single direction. The energy that is transferred to herbivores is not returned to the autotrophs. The energy that the autotrophs absorb does not go back to the Sun. As a result, energy in the food chain progresses through different trophic levels. The preceding trophic level can no longer access this energy. Consequently, a food chain’s energy flow is unidirectional.

The following are the ways that pesticides enter the food chain and ultimately enter our bodies:

i. Crop plants are treated with pesticides to keep pests away from them. These pesticides are absorbed by the plants after being washed into the soil or water bodies.
ii. Pesticides enter the food chain when plants are eaten by people or other animals. Because pesticides don’t biodegrade, they gradually accumulate in our bodies and get inside of us.

9. Non-biodegradable materials do not breakdown by the action of microorganisms. Will there be any effect of heat and pressure if they remain buried under the land for a long time?

Answer: No, if they are buried under the ground for a long time, neither heat nor pressure will affect them.

10. Non-biodegradable materials do not breakdown by the action of microorganisms. Will there be any effect of heat and pressure if they remain buried under the land for a Longtime?

Answer: No, heat and pressure won’t affect them if they’re buried under the ground for a long time.

11. State with reason any two possible consequences of elimination of decomposers from the earth.

Answer: There could be two negative effects if decomposers were removed from the earth: 

(i) There wouldn’t be any organic nutrients, and all the dead plants would destroy the habitat for the animals.
(ii) Because decomposition of waste materials would never occur, the ecosystem would be overflowing with plant and animal waste (due to the absence of decomposers).

12 (a) What would happen if the number of carnivores decreased in an ecosystem?
(b) What is an ecosystem? List its two main components.

Answer: (a) If the number of carnivores increases in an ecosystem, the number of herbivores will decrease. As a result, there will be fewer plants, which will lead to a reduction in atmospheric oxygen levels.

(b) An ecosystem is made up of all the living and inanimate components of an area that interact with one another. A garden, for instance, is an ecosystem made up of plants, insects, water, soil, and other elements. The ecosystem is made up of two parts: biotic and abiotic.

13. What do you mean by ozone depletion? Which compounds are responsible for the depletion of the ozone layer?

Answer: Ozone depletion is the term used to describe a decrease in the amount of ozone in the ozone layer. The main contributors to chemical ozone depletion caused by humans are chlorofluorocarbons (CFCs) and other halogenated ozone depleting substances (ODS).

14. If all the waste we generate is biodegradable, will this have no impact on the environment?

Answer: Biodegradable waste can decompose in our environment at a specific rate. Even though the waste is biodegradable, dumping massive amounts of it will pollute the environment. This is due to nature’s inability to properly decompose the waste into harmless materials. Biodegradable waste can lead to the following issues if it is produced in excess:

i. A bad smell is produced when large quantities of biodegradable waste rot in the open.
ii. Mountains of biodegradable waste serve as a haven for worms, flies, and mosquitoes, which spread a variety of diseases.
iii. Excessive amounts of biodegradable waste can also clog drains, which leads to unsanitary conditions and the growth of mosquitoes.
iv. Biodegradable waste buildup in bodies of water can cause issues like algal bloom, which results in a lack of dissolved oxygen and eutrophication.

15. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Answer: We are shielded from the sun’s harmful UV rays by the ozone layer. It protects the earth’s surface from the Sun’s ultraviolet (UV) radiation. This radiation is extremely harmful to living things; for instance, it is known to cause skin cancer in people.

Human skin cancer incidence has increased as a result of the earth’s atmosphere becoming less ozone-rich, which allows more dangerous UV rays to reach the surface.

The amount of CFCs released into the atmosphere needs to be decreased in order to lessen the harm to the ozone layer. Environmentally safe substitutes should be used in place of CFCs in fire extinguishers and refrigerants. Controlling the release of CFCs through industrial processes is also necessary.

Tick (✓) the correct option

1. The decomposers in an ecosystem:

Answer: (b) convert organic material to inorganic forms

2. Depletion of ozone is mainly due to:

Answer: (a) chlorofluorocarbon compounds

3. In a food chain, the third tropic level is always occupied by:

Answer: (a) carnivores

4. What will happen if deer are missing from the food chain given below?
Grass → Deer → Tiger

Answer: (d) the population of tiger decreases and the population of grass increases

5. Disposable plastic plates should not be used because:

Answer: (d) they are made of non-biodegradable materials

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