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Home , Natural environment

CHAPTER 12 OUR ENVIRONMENT: NATURAL AND I. KEY TERMS:

a. Environment : Surroundings of an , a or an object. b. Physical environment : The prevailing natural conditions such as land, and air. c. Biological environment : Environment which includes humans, and etc. d. : The thin layer of air which envelops our . e. : Layer of the earth comprising materials, extending to and basins. f. : Part of the earth’s surface covered with water. g. : A very narrow sphere of the earth which sustains . h. : Wide range of . II. ANSWER THESE QUESTION:

Q1. Why do we study natural environment? What is its importance? Ans. We study natural environment because all humans are influenced by the physical and natural environment. Not only beings but also plants and animals are influenced by the environment. Natural environment are quite necessary for the existence and development of human beings. Q2. What is atmosphere? Why is it important for us? Ans. The air-envelop that surrounds the earth is called the atmosphere Importance of the Atmosphere The atmosphere is very important to us. It has many advantages of its own: (1) The atmosphere acts like a blanket or a glass house for the earth. It receives the of the sun but does not allow the insulation to escape. As such, it keeps the earth warm. (2) Water vapours and dioxide present in the lower layers of the atmosphere absorb the heat radiated by the earth’s surface and keep the atmosphere warm even during night. (3) Had there been no atmosphere, the extremes of between the day and night would have been much greater. Q3. Why should we protect our environment? Ans. we should protect our environment because: 1. It provides us with various necessities of life such as air to breathe, water to drink, food to eat and land to live. 2. It provides us different natural like plants, wood, fuel, minerals and . 3. Irrational use of our natural resources like , pastures, farms, and minerals etc. would harm us to such an extent that no reform measures later on would do anything to repair the loss already done.

Q4. In which ways do the humans influence the environment?

Ans. Humans influence the environment in a number of ways : 1. If they go on cutting the jungles and trees mindlessly, they would soon cause the depletion of in the atmosphere. 2. If we go on using our mineral wealth indiscriminately, soon we would be deprived of this great gift of .

Q5. Why is the earth considered a unique planet? Ans. The earth is considered to be a unique planet in the due to the following factors : (1) The distance of the earth from the sun results in a which is best suited for the development of man and other forms of life on the earth. (2) It is a habitable planet. It supports man and other forms of life by providing all necessities of life. (3) Its atmosphere is rich in oxygen that makes life possible on this planet. (4) Its atmosphere acts as a large cover to protect its surface from extreme cold and heat. (5) On this planet (i.e. earth) water occurs in vast quantities which makes life possible on the earth, as water is essential for all forms of life. III . Answer briefly. Q1. What do you mean by environment? Ans. Environment means surroundings or conditions in which a person or a thing exists and develops his/its characteristics. For example, the environment of a refers to all those conditions which help the growth of that particular plant. Q2. Name the major spheres of environment. Ans. The major spheres of environment are the following :  Atmosphere  Lithosphere  Hydrosphere  Biosphere.

Draw it in copy with Ans 2.

Q3. Describe the composition of atmosphere. Ans. The atmosphere consists of a number of , which have almost same composition everywhere. Pure air consists of (78%), oxygen (21%), (0.9%) and (0.33%) etc. Besides these gases there are also to be found water vapours, , smoke, grains, salt and micro- in the lower layers of the atmosphere. Q4. What is biosphere? Ans. Life on earth exists in a narrow belt, a little below and above the surface of the land and in water and air. This narrow belt of living organisms, both plants and animals, is called biosphere. This sphere thus includes parts of atmosphere, lithosphere and hydrosphere. Importance of the Biosphere: The biosphere is the unique feature of our planet earth. The narrow belt of the biosphere makes it possible for millions of beings— organisms, both plants and animals — to survive and vary in size and shape. Q5. What do you mean by ecological balance? Ans. A proper interaction or balance between the natural environment and the human environment is quite necessary for the formation of favourable conditions for the survival of man. Such a balance is termed as the ecological balance. IV. Distinguish between : 1. Natural Environment and Human Environment. Ans. Natural Environment: All gifts such as land, water, air, plants and animals form a part of the natural environment. They include both biotic and abiotic resources. It is very necessary for existence and development for human beings. Human Environment: Human beings and their social, religious, economics and cultural activities form a part of the human environment. Eg : factories, towns, villages, roads, etc. 2. Sial and Sima. Ans. SIAL SIMA  Sial is the outer layer of earth’s .  Sima is the layer of the earth’s crust below sial.  It is composed of rocks rich in silica and aluminium;  It is composed of layers having materials rich in silica and magnesium  Its density is lower than Sima or the interior layer  Its density is higher than Sial. because density increases with depth.  It is exposed on the continents.  It forms the floors of the .

VII. Give reason. 1. areas are sparsely populated. Reason. Because the environment is very hot and harsh. 2. The (a) biosphere (b) hydrosphere (c) lithosphere – are important for us. Reason. a. The narrow belt of the biosphere makes it possible for millions of being-organisms, both plant and animals to survive and vary in size and shape. b. All these water bodies are quite necessary for the existence of life on this earth. Nor plants neither animals or humans can live without water. it is also a source of and chief agent of cooling the atmosphere. c. Its cover is indispensable for the growth of plants. Moreover, lithosphere is a source of various minerals resources including those of coal and oil. 3. We should be very careful in using our natural resources. Reason. a. Most of the natural resources are exhaustible resources. b. If we use them recklessly then very soon they will not be there for our future generation. c. Increasing population create big pressure on the resources. d. Not only quantity but quality of the resources has also reduced due to overuse of the them.

BOOK EXERCISES I.Choose the correct answer. 1. The density of the atmosphere decreases(a) with height. (a) decreases (b) increases (c) remains the same 2. The Sial is the outer(a) layer of the earth’s crust. (a) outer (b) middle (c) inner 3. The chief cooling agent of the atmosphere is the hydrosphere (b) (a) lithosphere (b) hydrosphere (c) biosphere 4. 71% ( c) of the earth is covered with water. (a) 80% (b) 79% (c) 71%

II.Write ‘T’ for true or ‘F’ for false statement. 1. We should protect the environment. ( T) 2. Sima is the outer layer of the crust. (F ) 3. Lithosphere is the source of various minerals. ( T) 4. Earth is sometimes called a watery planet. (T) 5. Biosphere is a very important part of the environment. (T) III.Fill in the blanks. 1. The environment can be divided into four spheres. 2. The envelop of air that surrounds the earth is called the atmosphere. 3. The average thickness of the lithosphere is 100 kilometres. 4. The part of the earth which is covered by water is called hydrosphere. 5. The narrow belt of living organisms is called the biosphere.