DAV Class 7 Science Chapter 15 Question Answer – Forests
Introduction
Forests are an important part of our environment. They provide food, timber, medicines and many other useful products. Forests are also home to a large variety of plants and animals. They help maintain the balance of oxygen and carbon dioxide, conserve soil and water, and support the water cycle.
In this chapter, we learn about the layers of a forest, food chains and food webs, the importance of forests, deforestation and the interdependence of living organisms.
Something To Know
A. Fill in the Blanks
1. Decomposers play an important role in __________ of nutrients.
Answer: Recycling
Explanation: Decomposers such as bacteria and fungi break down dead plants and animals. This returns nutrients to the soil, where they can be used again by plants.
2. Herbs are found in __________ layer of the forest.
Answer: Understory
Explanation: The understory is the layer below the canopy. It receives less sunlight, and small plants, shrubs and herbs commonly grow there.
3. Forests maintain a balance between __________ and __________ gases of the atmosphere.
Answer: Oxygen and carbon dioxide
Explanation: Plants take in carbon dioxide during photosynthesis and release oxygen. In this way, forests help maintain the balance of these gases in the atmosphere.
4. Overgrazing in forests may cause a decrease in soil __________ and an increase in soil __________.
Answer: Fertility, erosion
Explanation: Excessive grazing removes vegetation that protects the soil. This can reduce soil fertility and make the soil more easily carried away by wind and water.
5. __________ is the national tree of India.
Answer: Banyan
Explanation: The Banyan tree is the national tree of India. It is known for its large spreading branches and aerial roots.
B. Write True or False
1. Forests protect soil from erosion.
Answer: True
Explanation: Roots hold the soil together, while vegetation reduces the impact of rain and wind. Therefore, forests help prevent soil erosion.
2. Raw material for paper is obtained from forests.
Answer: True
Explanation: Wood and other plant materials obtained from forests can be used as raw materials for making paper.
3. Forests depend on man for water and fertilisers.
Answer: False
Explanation: Forest ecosystems generally maintain themselves naturally. They do not depend on humans for regular supply of water and fertilisers.
4. Plants and animals in a forest are not dependent on one another.
Answer: False
Explanation: Plants and animals are interdependent. Animals obtain food and shelter from plants, while plants benefit from animals in several ways, including pollination and seed dispersal.
5. Forests play an important role in water cycle.
Answer: True
Explanation: Trees release water vapour through transpiration. This contributes to moisture in the atmosphere and supports the water cycle.
C. Tick (✓) the Correct Option
1. The layer of forest, where intertwined branches of trees are found, is known as the—
Answer: (a) Canopy
Explanation: The canopy is formed by the branches and leaves of trees. The branches of neighbouring trees may become intertwined and form a continuous layer.
2. Decomposers help in
Answer: (b) Recycling of nutrients
Explanation: Decomposers break down dead organisms and return nutrients to the soil. These nutrients can then be used by plants.
3. An increase in cutting down of the trees in forests will lead to
Answer: (a) An increase in the amount of carbon dioxide in air
Explanation: Trees absorb carbon dioxide during photosynthesis. When many trees are removed, less carbon dioxide is absorbed, so its amount in the atmosphere can increase.
4. The tree, that is thought of as an ‘important tree’ is the
Answer: (c) Neem tree
Explanation: Neem is an important tree because it has many uses. Different parts of the neem tree are traditionally used for medicinal and other purposes.
5. The tree that is often referred to as ‘The golden shower tree’ is the
Answer: (c) Amaltas tree
Explanation: Amaltas is known as the Golden Shower Tree because its branches bear long clusters of bright yellow flowers.
D. Answer the Following Questions in Brief
1. Define the terms ‘food chain’ and ‘food web’.
Answer:
A food chain is a sequence that shows how food and energy pass from one organism to another.
A food web is a network of interconnected food chains in an ecosystem.
Explanation: In a forest, one organism may be eaten by different animals. Therefore, several food chains become connected to form a food web. For example:
Plants → Deer → Tiger
and
Plants → Insects → Birds → Eagle
Together, such connected chains form a food web.
2. Name the different layers of the forest.
Answer:
The four main layers of a forest are:
- Forest floor layer
- Understory layer
- Canopy
- Emergent layer
Explanation: Different plants and animals live in different layers according to the amount of sunlight, moisture and space available.
3. Give the meaning of the term ‘soil erosion’.
Answer:
Soil erosion is the removal of the fertile top layer of soil by agents such as wind and flowing water.
Explanation: Plant roots normally hold soil together. When vegetation is removed, soil becomes loose and can easily be carried away by wind or water.
4. Name four useful products that are provided to us by the forests.
Answer:
Four useful products obtained from forests are:
- Timber
- Firewood
- Lac
- Kendu leaves
Explanation: Forests provide many products that are useful in our daily lives and for various industries.
5. Name any four trees that are common to the Indian subcontinent.
Answer:
Four common trees are:
- Neem
- Banyan
- Peepal
- Deodar
Explanation: These trees are found in different regions of the Indian subcontinent and are important for the environment and people.
E. Answer the Following Questions
1. Comment on the statement: “Early man began his life as a forest dweller.”
Answer:
The statement is correct because early humans depended greatly on forests for their basic needs. They obtained fruits, roots and other food materials from plants and hunted animals for food. They also used wood, leaves and other forest materials for shelter and other purposes.
Explanation: Before the development of settled agriculture and modern societies, forests were an important source of food, shelter and materials for early humans. Thus, forests played an important role in the early life of humans.
2. How are the shapes of crown of trees, and their location on earth related to each other?
Answer:
The shape of a tree's crown is related to the amount and direction of sunlight received in a particular region.
Near the equator, tree crowns may be broad or spreading so that their leaves can receive plenty of sunlight. In colder regions such as those near the Arctic Circle, many trees have cone-shaped crowns. This shape helps them receive available sunlight and also helps snow slide off their branches.
Explanation: Plants adapt to the environmental conditions of the region in which they grow. Sunlight, temperature and snowfall can influence the shape of trees.
3. State any five points highlighting the importance of forests to mankind.
Answer:
Forests are important to humans in many ways:
- They provide habitats for many plants and animals.
- They provide useful products such as timber, fuel, fruits and medicinal materials.
- They help maintain the balance of oxygen and carbon dioxide.
- They help prevent soil erosion.
- They help maintain moisture in the atmosphere and support the water cycle.
- They contribute to soil fertility through the formation of humus.
- They help in the recharge of groundwater.
Explanation: Forests support both human life and wildlife. They provide natural resources while also performing important environmental functions.
4. Discuss, in brief, the likely consequences of deforestation.
Answer:
Deforestation means large-scale removal of trees and forests.
Some important consequences of deforestation are:
- The amount of carbon dioxide in the atmosphere may increase.
- Soil erosion increases because there are fewer roots to hold the soil.
- The natural recharge of groundwater may decrease.
- The chances of floods and droughts may increase.
- Many animals and plants lose their natural habitats.
- Loss of forests can contribute to loss of biodiversity.
- The balance of the water cycle can be disturbed.
Explanation: Forests perform many important ecological functions. Removing large areas of forest affects soil, water, climate and wildlife.
5. How are the Eucalyptus tree, Teak tree and the Neem tree important for us?
Answer:
- Eucalyptus: Its wood is useful in several industries, including the paper industry, and the tree is also associated with medicinal products.
- Teak: Teak wood is strong and durable and is widely used for making furniture and other wooden items.
- Neem: Neem has many useful properties, and different parts of the tree are traditionally used for medicinal and other purposes.
Explanation: Different trees provide different resources. Forests are therefore valuable sources of timber, medicines and industrial raw materials.
Value Based Questions
Sonu was a rather ‘self-centered’ boy and never cared to help others. His sister, Shweta, on the other hand, always showed empathy towards the needs of others and would go out of the way to help and guide others. Their mother advised Sonu to follow the example of his sister. She told him that all of us are interdependent on one another in much the same way as the many biotic and abiotic components of a forest are interdependent on one another.
1. State the values that you think Sonu needs to imbibe.
Answer:
Sonu needs to develop the following values:
- Helpful attitude
- Friendly behaviour
- Empathy
- Cooperation
- Caring for others
Explanation: We live in a society where people depend on one another. Helping others and understanding their needs makes society more caring and cooperative.
2. Name any two components of a forest and discuss their interdependence on each other.
Answer:
Two components of a forest are:
- Biotic components: Plants, animals, birds, insects and microorganisms.
- Abiotic components: Air, water, soil, sunlight and minerals.
Biotic and abiotic components depend on each other. Plants need sunlight, water, air and minerals to grow. Animals depend on plants for food and shelter, while decomposers help return nutrients to the soil.
Explanation: A forest is an ecosystem in which living and non-living components work together. A change in one component can affect other components.
Something To Do
1. Adopt a Tree
Question: Cutting down of trees is a major concern for mankind. Choose a tree near your school or house and prepare a scrapbook about it. You can find out its name in different languages as well as its scientific name. Draw pictures or click photographs of that tree. Also write how this tree is useful for the community, such as its medicinal value, providing shade, etc.
Answer: This is an activity-based question. Students should select a tree near their home or school and prepare a scrapbook.
Sample information:
Explanation: This activity helps students observe trees closely and understand their importance in everyday life.
2. Visit a Forest
Question: Visit a forest and make a list of animals and plants that you see. Try to prepare diagrammatic representations of food chains and food webs that exist in that forest.
Answer: This is an activity-based question. Students should record the plants and animals observed and prepare food chains from them.
Sample food chain:
Grass → Deer → Tiger
Another example:
Plants → Insects → Birds
Explanation: Food chains show the transfer of food and energy from one organism to another. Several connected food chains form a food web.
3. Make a List of Wildlife Sanctuaries and National Parks in India
Question: Make a list of wildlife sanctuaries and national parks in India. Try to locate them on the map.
Answer: Students can prepare a list such as:
| National Park/Wildlife Sanctuary | State/Union Territory |
|---|---|
| Jim Corbett National Park | Uttarakhand |
| Kaziranga National Park | Assam |
| Gir National Park | Gujarat |
| Kanha National Park | Madhya Pradesh |
| Ranthambore National Park | Rajasthan |
| Periyar National Park | Kerala |
Explanation: National parks and wildlife sanctuaries help protect wildlife, plants and their natural habitats. Locating them on a map also helps students understand their geographical distribution.
Important Points to Remember
- Forests are home to a large variety of plants and animals.
- A forest has different layers such as the forest floor, understory, canopy and emergent layer.
- Decomposers help in recycling nutrients.
- Plants and animals in a forest are interdependent.
- Forests help maintain the balance of oxygen and carbon dioxide.
- Forests help prevent soil erosion.
- Forests play an important role in the water cycle.
- Forests provide timber, firewood, medicines, fruits and many other useful products.
- Deforestation can cause soil erosion, habitat loss and disturbance of the water cycle.
- Conservation of forests is important for maintaining ecological balance.
Conclusion
Forests are essential for life on Earth. They provide natural resources, shelter wildlife, protect soil and water, and help maintain the balance of gases in the atmosphere. We should protect forests, plant more trees and use forest resources responsibly. Understanding the importance of forests helps us become responsible citizens and better protect our environment.
