NCERT Solutions for Class 7 Social Science – Our Environment Chapter 1 – Environment
Exercise : Solutions of Questions on Page Number : 6
Q1 : Answer the following questions.
(i) What is an ecosystem?
(ii) What do you mean by natural environment?
(iii) Which are the major components of environment?
(iv) Give four examples of human-made environment.
(v) What is lithosphere?
(vi) Which are the two major components of biotic environment?
(vii) What is biosphere?
Answer :
(i)Plants, animals and human beings depend on their immediate surroundings. They are often interdependent on each other as well. These relations of dependence and interdependence together constitute an ecosystem.
In other words, an ecosystem is the system formedas a result of the interactions of all living organisms with each other, and with the physical and chemical factors of the environment in which they live.
(ii)The environment that consists of all objects created by nature is called natural environment. The natural environment comprises land, water, air, plants and animals.
(iii)The major components of environment are natural environment (consists of all objects created by nature), human environment (consists of human beings) and human-made environment (consists of objects created by human beings).
(iv)Parks, buildings, roads and industries are some examples of human-made environment.
(v)Lithosphere (or the domain of land) is the solid crust or the hard top layer of the Earth. It is made up of rocks and minerals, and is covered by a thin layer of soil. It is an irregular surface with various landforms such as mountains, plateaus, plains and valleys.
(vi)The two major components of biotic environment are plants and animals.
(vii)Biosphere is the narrow zone of the Earth where land, water and air interact with each other to support life.
Q2 : Tick the correct answer.
(i) Which is not a natural ecosystem?
(a) Desert (b) Aquarium (c) Forest
(ii) Which is not a component of human environment?
(a) Land (b) Religion (c) Community
(iii) Which is a human-made environment?
(a) Mountain (b) Sea (c) Road
(iv) Which is a threat to environment?
(a) Growing plant (b) Growing population (c) Growing crops
Answer :
(i) Which is not a natural ecosystem?
(a) Desert (b) Aquarium
(c) Forest
(ii) Which is not a component of human environment?
(a) Land (b) Religion (c) Community
(iii) Which is a human-made environment?
(a) Mountain (b) Sea (c) Road
(iv) Which is a threat to environment?
(a) Growing plant (b) Growing population (c) Growing crops
Q3 : Match the following.
| (i) Biosphere | (a) Blanket of air which surrounds the Earth |
| (ii) Atmosphere | (b) Domain of water |
| (iii) Hydrosphere | (c) Gravitational force of the Earth |
| (iv) Environment | (d) Our surroundings |
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(e) Narrow zone where land, water and air interact |
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(f) Relation between the organisms and their surroundings |
Answer :
| (i) Biosphere | (e) Narrow zone where land, water and air interact |
| (ii) Atmosphere | (a) Blanket of air which surrounds the Earth |
| (iii) Hydrosphere | (b) Domain of water |
| (iv) Environment | (d) Our surroundings |
Q4 : Give reasons.
(i) Man modifies his environment
(ii) Plants and animals depend on each other
Answer :
(i)All living organisms depend on their immediate surroundings or environment. Human beings interact with their environment and modify it according to their needs. The primitive humans lived a simple life, and fulfilled their needs from the nature around them (by hunting, eating fruits, living on trees and in caves, etc.). With the progress of time, as life grew more and more complex, humans learnt newer ways to use their surroundings (growing crops, raising animals, setting up permanent settlements, etc.), for satisfying their growing needs. The discovery of fire, the invention of the wheel, the emergence of the barter system, the development of trade and commerce, the invention of the engine, the industrial revolution and the advancements in transportation and communication are some of the milestones on the road of human growth. While travelling on this road to development, humans have constantly modified all the three components of environment – natural (polluting the air by burning fuels), human (forming political and religious units) and human-made (using telephones lines for internet connectivity).
(ii)Not only are all plants, animals and human beings dependent on their environment, but they are also interdependent upon each other in several ways. For example, plants are eaten by animals as food. Through photosynthesis, plants produce oxygen, which is necessary for the survival of all living organisms. Forests are the natural habitats of wild animals, while the woods of trees are used by humans for various purposes like building houses, boats, furniture, etc.
On the other hand, animals help plants reproduce by helping in the pollination of seeds. Nitrogen is essential for the survival of plants, and they are provided with this nitrogen by the bacteria that live in the soil and in the roots of some plants. Photosynthesis, which is the way by which plants make their food, depends upon factors like sunlight, water and carbon dioxide. The carbon dioxide is provided by humans and animals through respiration.