---
title: "NCERT Solutions for Class 10 Science Chapter 13 Our Environment"
url: https://www.swavid.com/science/class/10/chapter/our-environment/ncert-solutions
dateModified: 2026-10-07T16:48:22+00:00
---

# NCERT Solutions for Class 10 Science Chapter 13 Our Environment

This chapter's questions cover concepts related to ecosystems, food chains, energy flow, biological magnification, environmental problems, ozone layer depletion, and waste disposal.

Free PDF (8 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-10/swavid-ncert-solutions-class-10-science-chapter-13-our-environment-cd9439aa3d.pdf

## QUESTIONS

### Question 1

*3 marks · Short answer*

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

**Solution**

1. Each step or level of the food chain forms a trophic level.
2. Example of a food chain in a grassland: Grass (Producer) $\rightarrow$ Deer (Herbivore/Primary consumer) $\rightarrow$ Lion (Carnivore/Secondary consumer).
3. The different trophic levels in this food chain are: first trophic level is grass, second trophic level is deer, and third trophic level is lion.

**Answer:** Trophic levels are the various steps in a food chain where transfer of energy takes place. In the food chain Grass $\rightarrow$ Deer $\rightarrow$ Lion, grass is at the first, deer at the second, and lion at the third trophic level.

> Common mistake: Students often confuse trophic levels with food web or forget to mention the specific organisms for each level in the given example.

### Question 2

*3 marks · Short answer*

What is the role of decomposers in the ecosystem?

**Solution**

1. Microorganisms like bacteria and fungi act as decomposers in the ecosystem.
2. They break down the complex organic substances of dead remains and waste products of organisms into simple inorganic substances.
3. These simple substances go into the soil and are used up once more by the plants, thereby helping in the natural replenishment of the soil.

**Answer:** Decomposers break down the complex organic substances of dead plants and animals into simple inorganic substances that enrich the soil and are reused by plants.

> Common mistake: Students sometimes miss writing that the inorganic nutrients released by decomposers are reabsorbed by plants.

## QUESTIONS

### Question 1

*3 marks · Short answer*

Why are some substances biodegradable and some non-biodegradable?

**Solution**

1. Substances are broken down by biological processes in nature due to specific enzymes produced by decomposers like bacteria and fungi.
2. Substances that can be broken down by biological processes are called biodegradable substances.
3. Enzymes are highly specific in their action, so substances like plastics cannot be broken down by these enzymes and persist unchanged, making them non-biodegradable.

**Answer:** Substances are biodegradable if biological organisms like bacteria and fungi have specific enzymes to break them down; otherwise, they are non-biodegradable.

> Common mistake: Stating that non-biodegradable substances never break down at all, ignoring physical processes like heat and pressure.

### Question 2

*3 marks · Short answer*

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

**Solution**

1. Biodegradable substances are broken down by microorganisms into simple inorganic substances that naturally replenish the soil.
2. Excessive accumulation of biodegradable waste can produce foul smells and act as a breeding ground for harmful disease-causing vectors like mosquitoes and flies.
3. Proper decomposition recycles nutrients back into the ecosystem, maintaining ecological balance.

**Answer:** Biodegradable substances replenish soil nutrients upon decomposition, but in excess, they can cause foul odours and act as breeding sites for disease vectors.

> Common mistake: Assuming biodegradable waste has zero negative impact on the environment.

### Question 3

*3 marks · Short answer*

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

**Solution**

1. Non-biodegradable substances like plastics persist in the environment for a long time without undergoing degradation, causing long-term pollution.
2. They can harm various members of the ecosystem, such as choking aquatic or terrestrial animals when ingested.
3. They can block soil pores and hinder natural water seepage into the ground.

**Answer:** Non-biodegradable substances persist for long periods causing environmental pollution and can harm living organisms by ingestion or blocking soil percolation.

> Common mistake: Confusing non-biodegradable effects with biological magnification without mentioning physical persistence.

## QUESTIONS

### Question 1

*3 marks · Short answer*

What is ozone and how does it affect any ecosystem?

**Solution**

1. Ozone ($O_3$) is a molecule formed by three atoms of oxygen, unlike normal molecular oxygen ($O_2$) which has two atoms.
2. At the higher levels of the atmosphere, ozone performs an essential function by shielding the surface of the earth from ultraviolet (UV) radiation from the Sun.
3. UV radiation is highly damaging to organisms, causing health issues such as skin cancer in human beings, thereby protecting the ecosystem from its harmful effects.

**Answer:** Ozone is a molecule of three oxygen atoms that shields the Earth's surface from harmful UV radiation, protecting ecosystems from damage.

> Common mistake: Confusing normal oxygen ($O_2$) with ozone ($O_3$) or missing the protective role of ozone against UV rays.

### Question 2

*3 marks · Short answer*

How can you help in reducing the problem of waste disposal? Give any two methods.

**Solution**

1. We can reduce the problem of waste disposal by adopting the 3 Rs: Reduce, Reuse, and Recycle.
2. We can separate biodegradable and non-biodegradable waste into separate dustbins before disposal so that they can be treated accordingly.
3. We can prepare compost from biodegradable kitchen waste to enrich the soil.

**Answer:** We can help by following the 3 Rs (Reduce, Reuse, Recycle) and by separating biodegradable and non-biodegradable wastes.

> Common mistake: Writing general statements without mentioning specific methods like segregation of waste or the 3 Rs.

## EXERCISES

### Question 1

*1 mark · MCQ*

Which of the following groups contain only biodegradable items?

- Grass, flowers and leather
- Grass, wood and plastic
- Fruit-peels, cake and lime-juice
- Cake, wood and grass

**Solution**

1. Substances that are broken down by biological processes are said to be biodegradable.
2. Plastic is a human-made synthetic material that cannot be broken down by bacteria or saprophytes, making option (b) incorrect.

**Answer:** (d) Cake, wood and grass

> Common mistake: Including items like plastic or synthetic materials which persist in the environment for a long time.

### Question 2

*1 mark · MCQ*

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**

1. A food chain represents a series of organisms feeding on one another where energy flows linearly.
2. In option (b), grass (producer) is eaten by goat (herbivore), which is eaten by human (carnivore/omnivore), forming a valid food chain.

**Answer:** (b) Grass, goat and human

> Common mistake: Selecting groups of organisms that do not feed on each other in nature.

### Question 3

*1 mark · MCQ*

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**

1. Environment-friendly practices help in conserving resources and reducing pollution.
2. Carrying cloth bags, switching off unnecessary lights and fans, and walking to school instead of using motorized transport all reduce environmental impact.

**Answer:** (d) All of the above

> Common mistake: Selecting only one individual good practice instead of all options.

### Question 4

*3 marks · Short answer*

What will happen if we kill all the organisms in one trophic level?

**Solution**

1. If we kill all the organisms in one trophic level, it will cause a severe disruption in the food chain and the entire ecosystem.
2. The organisms in the previous trophic level will increase excessively in number due to the lack of predators.
3. The organisms in the subsequent trophic level will starve and die due to the complete lack of food.

**Answer:** Killing all organisms in one trophic level breaks the food chain, causing overpopulation of the lower level and starvation of the higher level.

> Common mistake: Forgetting to mention the effect on both the lower and higher trophic levels.

### Question 5

*3 marks · Short answer*

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**

1. Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels.
2. Removing producers would collapse the entire ecosystem as they provide the primary energy fixed from sunlight.
3. No organisms from any trophic level can be removed without causing severe damage and imbalance to the ecosystem.

**Answer:** The impact varies by level, and removing any trophic level completely disrupts and damages the ecosystem.

> Common mistake: Assuming that higher trophic levels can be removed without any consequence.

### Question 6

*3 marks · Short answer*

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

**Solution**

1. Biological magnification is the progressive accumulation of non-biodegradable harmful chemicals (like pesticides) at each higher trophic level in a food chain.
2. Yes, the levels of this magnification will be different at different trophic levels.
3. Since human beings or top carnivores occupy the highest trophic level, the maximum concentration of these harmful chemicals gets accumulated in our bodies.

**Answer:** Biological magnification is the increase in concentration of harmful chemicals at successive trophic levels, being highest at the top level.

> Common mistake: Confusing biological magnification with energy flow or stating that chemical concentration remains uniform.

### Question 7

*3 marks · Short answer*

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

**Solution**

1. Non-biodegradable wastes are inert and persist in the environment for a very long time without being broken down by biological processes.
2. They act as a source of harm to the various members of the ecosystem and cause pollution of soil and water resources.
3. They undergo biological magnification, accumulating progressively at each trophic level and harming higher organisms including humans.

**Answer:** Non-biodegradable wastes persist for a long time, cause environmental pollution, and lead to biological magnification in food chains.

> Common mistake: Confusing non-biodegradable wastes with biodegradable wastes or forgetting to mention biological magnification.

### Question 8

*3 marks · Short answer*

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

**Solution**

1. Even if all the waste we generate is biodegradable, it will still have an impact on the environment.
2. Large amounts of biodegradable waste decomposing at the same time can release foul gases and pollute the surroundings.
3. It can also act as a breeding ground for harmful insects and disease-causing vectors, affecting public health.

**Answer:** Yes, biodegradable waste will still impact the environment by causing foul smells, pollution, and acting as a breeding ground for pests if not managed properly.

> Common mistake: Assuming biodegradable waste causes zero environmental problems.

### Question 9

*3 marks · Short answer*

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

**Solution**

1. Damage to the ozone layer is a cause for concern because the ozone layer shields the surface of the Earth from ultraviolet (UV) radiation from the Sun.
2. UV radiation is highly damaging to organisms and is known to cause skin cancer in human beings.
3. To limit this damage, the United Nations Environment Programme (UNEP) succeeded in forging an agreement in 1987 to freeze CFC (chlorofluorocarbon) production at 1986 levels, and it is now mandatory for manufacturing companies to make CFC-free refrigerators worldwide.

**Answer:** Damage to the ozone layer allows harmful UV rays to reach Earth, causing skin cancer. Steps taken include freezing CFC production at 1986 levels as per the UNEP agreement.

> Common mistake: Forgetting to mention the role of UNEP or CFC freeze agreement in controlling ozone depletion.

## Frequently asked questions

### How many questions and exercises are there in the NCERT solutions for Class 10 Science Chapter 13?

This chapter contains a total of 7 textbook questions across two specific sets and 9 questions in the main exercises. SwaVid provides complete step-by-step solutions for all these questions in the free PDF available on this page.

### Which topics are covered in the questions of this chapter?

The questions cover important concepts such as biodegradable and non-biodegradable substances, trophic levels, food chains, the role of decomposers, and the ozone layer. Other key topics include biological magnification, waste disposal management methods, and environment-friendly practices.

### What is the hardest question type in this chapter and how should I approach it?

Questions involving biological magnification and the removal of trophic levels in food chains are often considered the most challenging. To approach them, you should carefully analyze the flow of energy and toxins through each trophic level before drafting your response.

### How can I write answers in the exam to score full marks?

To score full marks in Class 10 Science, structure your answers with clear headings, bullet points, and proper scientific terms like $O_3$ for ozone or specific trophic level names. You can refer to SwaVid's free PDF on this page to understand the ideal answer formatting for each question type.

### Is the PDF for these solutions available for free download?

Yes, the complete set of solutions for this chapter is completely free to access. You can view the detailed explanations and download the free PDF directly from this SwaVid page to help with your exam preparation.

## Related pages

- [Our Environment: CBSE previous year questions](https://www.swavid.com/cbse/class-10/science/pyq/our-environment)
- [Class 10 Science chapters](https://www.swavid.com/science/class/10)

Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student