CBSE Class 7 Science Chapter 17 Forests: Our Lifeline NCERT Solutions

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

NCERT Solutions PDF Class 7 PDF

This comprehensive set of NCERT Solutions for CBSE Class 7 Science, Chapter 17, "Forests: Our Lifeline," delves into the critical role forests play in our ecosystem. The solutions explain how forests prevent floods by absorbing rainwater, how animals contribute to forest regeneration through seed dispersal and decomposition, and the vital function of decomposers like fungi and bacteria in nutrient cycling. It also highlights the forest's role in maintaining atmospheric balance by regulating oxygen and carbon dioxide levels, and why forests are natural recycling systems with no waste. Furthermore, students will learn about the various products obtained from forests and complete fill-in-the-blank exercises reinforcing key concepts. These solutions are designed to provide clear, step-by-step explanations, aiding students in understanding complex ecological processes and preparing effectively for their exams.

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Quick info

Board	CBSE
Class	Class 7
Subject	Science
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 17

Chapter summary

Chapter 17, "Forests: Our Lifeline," focuses on the ecological significance of forests. The NCERT Solutions cover the functions of forests, including flood prevention, seed dispersal by animals, and the role of decomposers. It emphasizes how forests maintain atmospheric gas balance and act as natural recycling systems. The chapter also lists essential forest products and includes exercises to test understanding of forest layers and nutrient cycling.

Learning outcomes

Understand the role of animals in forest regeneration and seed dispersal.
Explain how forests prevent floods.
Identify decomposers and their function in forests.
Describe the importance of forests in balancing atmospheric oxygen and carbon dioxide.
Recognize forests as natural recycling systems.
List various products obtained from forests.

Topics covered

Paper topics

Role of animals in forests
Seed dispersal
Forests and flood prevention
Decomposers (fungi, bacteria)
Humus formation
Nutrient cycling
Oxygen-carbon dioxide balance
Forests as recycling systems
Products from forests
Forest layers (herb layer)

Important topics

Functions of forests (flood prevention, atmospheric balance)
Role of decomposers
Forests as recycling systems
Importance of biodiversity in forests

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Questions and Solutions

Question 1

Explain how animals dwelling in the forest help it grow and regenerate.

Solution: Animals play a crucial role in the growth and regeneration of forests through several mechanisms. Firstly, many animals, especially birds and mammals, consume fruits and seeds. As they move through the forest, they disperse these seeds through their droppings, helping new plants to grow in different areas. Secondly, when animals die, their bodies decompose and add vital nutrients to the soil. Similarly, their excreta also acts as a natural fertilizer. Microorganisms further break down this organic matter into humus, which is rich in nutrients and essential for healthy plant growth. This continuous process ensures the forest ecosystem remains vibrant and self-sustaining.

Question 2

Explain how forests prevent floods.

Solution: Forests act as a natural sponge, significantly helping to prevent floods. The dense canopy of trees intercepts rainwater, causing it to fall more gently to the forest floor instead of hitting the ground with force. The thick layer of leaf litter and the extensive root systems of trees and other plants on the forest floor absorb a large amount of this rainwater. This absorption process slows down the water's journey, allowing it to seep gradually into the soil. By reducing the speed and volume of surface runoff, forests prevent water from accumulating rapidly and overwhelming river systems, thereby mitigating the risk of floods.

Question 3

What are decomposers? Name any two of them. What do they do in the forest?

Solution: Decomposers are microorganisms, such as certain types of bacteria and fungi, that play a vital role in forest ecosystems. Their primary function is to break down dead and decaying organic matter, including dead plants, leaves, and animals. Through this process, they convert complex organic materials into simpler substances, forming humus. Humus is a nutrient-rich component that mixes with the soil, providing essential minerals and nutrients necessary for the growth of plants and trees. Therefore, decomposers are crucial for nutrient cycling and maintaining the fertility of the forest soil.

Question 4

Explain the role of forest in maintaining the balance between oxygen and carbon dioxide in the atmosphere.

Solution: Forests are essential for maintaining the atmospheric balance of oxygen and carbon dioxide. Plants within the forest perform photosynthesis, a process where they utilize carbon dioxide from the atmosphere and release oxygen as a byproduct. Simultaneously, animals and plants respire, consuming oxygen and releasing carbon dioxide. Forests, with their vast number of plants, absorb a significant amount of atmospheric carbon dioxide, thereby regulating its concentration. The oxygen produced during photosynthesis replenishes the atmosphere, ensuring a stable supply for respiration. This continuous exchange helps maintain the delicate balance required for life on Earth.

Question 5

Explain why there is no waste in a forest.

Solution: A forest functions as a highly efficient, natural recycling system, which is why there is virtually no waste. All components of the forest ecosystem are interconnected through food chains and food webs. Plants form the base, providing food for herbivores, which in turn are eaten by carnivores. When any organism dies, its remains are broken down by decomposers (like bacteria and fungi) into nutrients. These nutrients are then absorbed by the soil and utilized by plants for growth. This continuous cycle of consumption, death, decomposition, and nutrient uptake ensures that all organic matter is eventually reused, preventing the accumulation of waste.

Question 6

List five products we get from forests?

Solution: Forests provide a wide variety of essential products. Five important products obtained from forests include:

Timber and wood (used for furniture, construction, paper)
Fruits and vegetables (wild edible plants)
Medicines and herbs (various medicinal plants)
Resins, gums, and latex (used in industries, for rubber production)
Spices and essential oils

Question 7

Fill in the blank:

The insects, butterflies, honeybees and birds help flowering plants in ______.
A forest is a purifier of _____ and _____.
Herbs form the _____ layer in the forest.
The decaying leaves and animal droppings in a forest enrich the ______.

Solution:

The insects, butterflies, honeybees and birds help flowering plants in pollination.
A forest is a purifier of air and water.
Herbs form the lowest layer in the forest.
The decaying leaves and animal droppings in a forest enrich the soil.

Common mistakes

Confusing the roles of different forest layers.
Not fully understanding the process of decomposition and its importance.
Underestimating the impact of forests on atmospheric gas balance.

Revision tips

Focus on understanding the interconnectedness of living organisms within a forest ecosystem.
Draw diagrams to illustrate the food web and nutrient cycling in forests.
Memorize the key functions of forests, such as flood prevention and atmospheric regulation.
Practice the fill-in-the-blank questions to reinforce vocabulary and concepts.

Practice MCQs

Q1. Which of the following organisms help in the dispersal of seeds in a forest?

Q2. What is the primary role of decomposers in a forest?

Q3. How do forests help in preventing floods?

Q4. Which process do plants in a forest use to take in carbon dioxide?

Q5. Which of the following is NOT a product obtained from forests?

Frequently asked questions

What is the main role of forests mentioned in Chapter 17?

Forests are vital 'lifelines' that prevent floods, maintain the balance of oxygen and carbon dioxide in the atmosphere, and act as natural recycling systems.

How do animals help forests grow and regenerate?

Animals aid in seed dispersal by carrying seeds to new areas and contribute nutrients to the soil through their droppings and decomposed bodies.

What are decomposers and why are they important?

Decomposers are microorganisms like fungi and bacteria that break down dead plants and animals into humus, enriching the soil with essential nutrients for plant growth.

How do forests help in maintaining the balance of gases in the atmosphere?

Plants in forests absorb carbon dioxide during photosynthesis and release oxygen, counterbalancing the carbon dioxide released by animals during respiration.

Can you list some products we get from forests?

Yes, forests provide us with timber, fruits, vegetables, spices, medicines, gum, latex (for rubber), and turpentine.

Why are forests considered natural recycling factories?

In forests, dead organic matter is decomposed into nutrients, which are then used by plants. This continuous cycle ensures that nothing goes to waste.

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