CBSE Class 10 Science NCERT Solutions: Chapter 15 Our Environment

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 10 PDF

This chapter delves into the fundamental concepts of our environment, crucial for Class 10 Science students. The NCERT Solutions cover key topics such as the definition and types of ecosystems, including artificial and natural ones. It explains the structure of food chains, the flow of energy across different trophic levels, and the roles of producers, consumers, and decomposers. The solutions also address critical environmental issues like pollution, ozone depletion, and the process of biomagnification, explaining how non-biodegradable substances accumulate in the food chain. These detailed explanations and step-by-step solutions are designed to help students grasp complex ecological principles and prepare effectively for their board examinations.

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Quick info

Board	CBSE
Class	Class 10
Subject	Science (Exemplar)
Session	2026
Language	English
Type	NCERT Solutions
Chapter	15. Our Environment

Chapter summary

Chapter 15, Our Environment, focuses on ecological concepts vital for Class 10 Science. The NCERT Solutions explain the components of an ecosystem, differentiating between natural and artificial types. They detail the structure of food chains and the energy transfer between trophic levels, emphasizing the 10% energy law. Key environmental problems like pollution, ozone depletion caused by CFCs, and biomagnification are also covered, providing clear definitions and explanations.

Learning outcomes

Understand the concept of an ecosystem and its components.
Differentiate between natural and artificial ecosystems.
Explain the structure and functioning of food chains.
Describe the flow of energy across different trophic levels.
Identify and explain environmental issues like pollution and ozone depletion.
Define and illustrate the process of biomagnification.

Topics covered

Paper topics

Ecosystems
Artificial Ecosystems
Natural Ecosystems
Food Chains
Trophic Levels
Energy Flow in Ecosystems
Pollution
Ozone Depletion
Biomagnification
Non-biodegradable substances

Important topics

Ecosystem structure and function
Food chains and trophic levels
Energy transfer (10% law)
Biomagnification
Ozone depletion

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Questions and Solutions

Multiple Choice Questions

1. Which one of the following is an artificial ecosystem?

Solution: The correct answer is (b) Crop field. A crop field is an ecosystem that is created, managed, and maintained by humans. Unlike natural ecosystems such as ponds, lakes, or forests, it relies on human intervention for its functioning and productivity.

2. In a food chain, the third trophic level is always occupied by

Solution: The correct answer is (a) carnivores. In a typical food chain, the first trophic level consists of producers (like plants), the second trophic level consists of herbivores (primary consumers that eat producers), and the third trophic level is usually occupied by carnivores (secondary consumers that eat herbivores).

3. An ecosystem includes

Solution: The correct answer is (c) both living organisms and non-living objects. An ecosystem is defined as a complex system comprising all the living organisms (biotic components) within a given area, along with their physical environment (abiotic components like air, water, soil, sunlight), and the interactions that occur between them.

Energy Flow in Food Chain

4. In the given food chain, suppose the amount of energy at the fourth trophic level is 5 kJ, what will be the energy available at the producer level?

$Grass \rightarrow Grasshopper \rightarrow Frog \rightarrow Snake \rightarrow Hawk$

Solution: The correct answer is (d) 5000 kJ. According to the 10% law of energy transfer in ecosystems, only about 10% of the energy from one trophic level is transferred to the next higher trophic level. The remaining 90% is lost as heat or used for metabolic processes. Therefore, if the energy at the fourth trophic level (Hawk) is 5 kJ, the energy at the third trophic level (Snake) would be

5 \times 10 = 50

kJ. The energy at the second trophic level (Frog) would be

50 \times 10 = 500

kJ. Finally, the energy available at the producer level (Grass), which is the first trophic level, would be

500 \times 10 = 5000

kJ.

5. Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as

Solution: The correct answer is (c) biomagnification. Biomagnification refers to the increasing concentration of a substance, such as a toxic chemical or pesticide, in the tissues of organisms at successively higher levels in a food chain. Eutrophication is the enrichment of water bodies with nutrients, and pollution is the introduction of harmful substances into the environment.

6. Depletion of ozone is mainly due to

Solution: The correct answer is (a) chlorofluorocarbon compounds. Chlorofluorocarbon compounds (CFCs), commonly used in refrigerants, aerosols, and solvents, are the primary cause of ozone layer depletion. When CFCs reach the stratosphere, they release chlorine atoms that catalytically destroy ozone molecules.

Common mistakes

Confusing producers, herbivores, and carnivores in food chains.
Miscalculating energy transfer between trophic levels.
Confusing terms like eutrophication and biomagnification.
Not identifying the correct cause for ozone depletion.

Revision tips

Draw diagrams of food chains to visualize trophic levels.
Memorize the 10% energy transfer rule for food chains.
Create flashcards for key environmental terms like biomagnification.
Review the causes and effects of ozone depletion and pollution.

Practice MCQs

Q1. Which of the following is an example of an artificial ecosystem?

Q2. In a typical food chain, what is always found at the third trophic level?

Q3. An ecosystem is defined as the interaction between:

Q4. If the energy at the fourth trophic level of a food chain is 5 kJ, what is the energy available at the producer level?

Q5. The increasing accumulation of non-biodegradable pesticides in organisms at successively higher trophic levels is called:

Q6. Which compounds are primarily responsible for the depletion of the ozone layer?

Frequently asked questions

What is an ecosystem?

An ecosystem is a community of living organisms (biotic components) interacting with each other and their non-living physical environment (abiotic components) in a particular area.

What is the difference between a natural and an artificial ecosystem?

A natural ecosystem, like a forest or pond, develops and functions on its own without human intervention. An artificial ecosystem, such as a crop field or aquarium, is created and managed by humans.

How does energy flow through a food chain?

Energy flows from producers to consumers. According to the 10% law, only about 10% of the energy from one trophic level is transferred to the next; the rest is lost as heat.

What is biomagnification?

Biomagnification is the process where non-biodegradable substances, like pesticides, accumulate in organisms and increase in concentration at each successive trophic level in a food chain.

What causes ozone depletion?

Ozone depletion is primarily caused by chlorofluorocarbon compounds (CFCs) and other ozone-depleting substances that release chlorine and bromine atoms in the stratosphere, which destroy ozone molecules.

How can these NCERT solutions help in exam preparation?

These solutions provide clear, step-by-step explanations for all questions, helping students understand complex ecological concepts, revise key topics, and practice problem-solving for their exams.

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