6th std science 1 natural resources-air, water and land l question and answer explanation in marathi

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Science Studies -  6th Standard

1. Natural Resources – Air, Water, Land

Question And Answer

Q.1 Fill in the blanks.

1) The layer of ozone gas absorbs ultra violet rays that come from the sun to the earth.

2) Of the total water available on the earth, fresh water forms 0.3 percent.

3) Both biotic and abiotic constituents are present in the soil.

Q.2 Why is it said that- ?

1) The ozone layer is a protective shell of the earth.

Ans: 1) Our sun emits ultra violet rays which are harmful to human beings. They can cause skin cancer.

2) The ozone layer absorbs these harmful rays. Therefore, it is said that the ozone layer is a protective shell of the earth.

2) Water is life.

Ans: 1) We require water for drinking.

2) The blood of animals and sap of plants contain water.

3) We depend on plants for our food.

4) Water is also required for various other purposes like maintaining cleanliness, construction etc. Therefore, it is said that water is life.

3) Seawater is useful even though it is not potable.

Ans: 1) Water vapours are formed from sea water.

2) These vapours further form clouds.

3) From these clouds, we get rain water which is fresh water.

4) Thus seawater is a source of fresh water. Therefore, it is said that seawater is useful even though it is not potable.

Q.3 What will happen if-

1) Microbes in the soil get destroyed.

Ans: 1) Some of the microbes in the soil are useful to us.

2) They decompose the parts of dead animals and plants and form humus.

3) Humus contains a lot of nutrients which are required by plants.

4) Due to humus, land becomes aerated and it holds water for longer time. This is also helpful for growth of plants.

5) If microbes are destroyed, humus will not be formed and plants will not grow properly. As a result, we will not get food and we will not survive.

2) The number of vehicles and factories in your surroundings increases.

Ans: 1) If the number of vehicles increases, the proportion of carbon dioxide and other pollutant gases will increase.

2) If the number of factories increase, some of the exhaust gases may pollute the air.

3) Due to pollution of air, many diseases like respiratory system disorder, greenhouse effect may be caused and the temperatures may increase.

4) Some of the pollutants may destroy the ozone layer which absorbs the harmful ultra-violet rays. This will result into reaching these rays to that region and may cause skin cancer.

3) The total supply of potable water is finished.

Ans: 1) We require potable water for drinking.

2) Drinking water is essential for our survival.

3) If the total supply of potable water is finished, we will have to obtain potable water from the salty sea-water.

4) This is a costly process and we will have to purchase potable water at a very high price.

Q.4 Match the following.

Q.5 Name the following.
1) Constituents of the biosphere-

Ans: 1) Atmosphere 2) Lithosphere 3) Hydrosphere

2) Biotic constituents of soil-

Ans: 1) Microbes 2) Worms 3) Insects 4) Rodents

3) Fossil fuel-

Ans: 1) Petrol 2) Diesel 3) Kerosene 4) Paraffin

4) Inert gases in air-

Ans: 1) Argon 2) Hellium 3) Neon 4) Krypton 5) Xenon

5) Gases that are harmful to ozone layer-

Ans: 1) Carbon tetrachtoride 2) Chloroflurocarbons

Q.6 True or false ?

1) Land and soil are the same thing – False

2) The water in a lake is called ground water- False

3) It takes about 1000 years to form a 25 cm thick layer of soil- False

4) Radon is used in decorative lights- False

Q.7 Answer in your own word.

1) Explain with the help of a diagram how soil is formed.

Ans: 1) Due to heat, cold, wind, rain and flowing water, the bedrock is broken in to pieces. This is called as the weathering of bedrocks.

2) Because of this, the stones, sand and soil are formed.

3) The growing roots of trees also help in breaking the rocks. Thus the soil is formed.

2) Why is there a shortage of water even though it occupies about 71% of the earth’s surface?

Ans: 1) Though 71% of the earth’s surface is occupied by the water, only 0.3% of total water on the earth is fresh water available for drinking.

2) Rain is the source of this fresh water.

3) If in a particular region rain fall is not sufficient then that region experiences shortage of water.

3) What are the various constituents of air? Write their uses.

Ans: The various constituents of air and d the necessary proteins. It is useful in the production their uses are as follows:

1) Nitrogen- Helps living things to blind the necessary proteins. It is useful in the production of ammonia and in airtight packaging of foodstuffs.

2) Oxygen- Necessary for respiration in living things and for combustion.

3) Carbon dioxide- Plants use it for producing their food. Used in fire extinguishers.

4) Argon- Used in electric bulbs.

5) Helium- Used for obtaining low temperature and also for generating lift in airships.

6) Neon- Used in decorative lights and for street lighting

7) Krypton- Used in fluorescent tubes

8) Xenon- Used in flash photography

4) Why are air, water and land considered to be valuable natural resources?

Ans: 1) Air is necessary for respiration of all living things. Without air living things cannot survive.

2) Water is also very important for living things. The survival of all living things is possible only if water is available.

3) Land is necessary to build shelters for us. Land is requires for agriculture and it provides us with many useful minerals.

4) Thus air, water and land satisfy our basic needs. But their availability is limited. So air, water and land are considered to be valuable natural resources.

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