Page 101 - SST Class 07

4. ______________ consists of seas, oceans and other water bodies surrounding the earth.
5. Nitrogen constitutes about ______________ of the earth’s atmosphere.
6. ______________ is needed by the plants to prepare their food.

E. Answer in one word or phrase :
1. What do you mean by environment?
2. List some abiotic components.
3. What do you understand by the term lithosphere?
4. What does the hydrosphere comprise of?
5. What does the atmosphere protect us from?
6. What is the narrow contact zone of land, water and air which supports life called as?

F. Answer the questions in brief :
1. What are the realms of natural environment?
2. Distinguish between biotic and abiotic components.
3. Why is atmosphere important to us?
4. Write a short note on hydrosphere.

5. Why do man modify the environment?
6. How can we maintain the balance of nature?
G. Answer the questions in detail :
1. What is environment? Describe its components.
2. How would you differentiate between natural and human environment?
3. Write a short note on lithosphere.
4. What is the significance of the biosphere?

5. Give an account of the human environment.
6. How man is changing environment?

1. How do human activities in the modern world cause ecological imbalances in the natural
environment?
2. How would be life without air?

Ecological Balance
Ecological balance is a term describing how ecosystems are organised in a state of stability where
species coexist with other species and with their environment.
Even if an ecosystem is balanced, that does not mean that no changes ever occur. A windstorm might
roll through wiping out a swathe of trees, a predator might be overhunted, or a drought might reduce
the availability of food resources. These ecological changes are called disturbances. A disturbance is any
change that causes a disruption in the balance of an ecosystem.

Environment
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