General Science Solutions Solutions for Class 6 Science Chapter 1 - Natural Resources – Air, Water And Land

Answer:

(a) The layer of ozone gas absorbs UV rays that come from the sun to the earth.
(b) Of the total water available on the earth, fresh water forms 0.3 percent.
(c) Both biotic and abiotic constituents are present in the soil.

Answer:

• Water from oceans can be used for making hydroelectricity, a form of renewable source of energy.
• It can be used as a cheap transport method.
• They can be used for the activities like scuba diving, water sports etc. which is a means of boosting the tourism and economic growth of a country.
• Nuclear power plants require coolants like water to bring down the temperature of the reactors. For this purpose several gallons of water is required and this demand is fulfilled by the water from oceans.
• They support a variety of flora and fauna which have both ecological and economical value.

Answer:

a. Soil contains various kinds of microbes like bacteria, fungi, algae, protozoa etc. All of these microorganisms play an important roles like:

• Certain bacteria and blue-green algae have the ability to fix atmospheric nitrogen. This, in turn, enriches the fertility of soil. Such microorganisms are known as biological nitrogen-fixers. Example − Rhizobium is a symbiotic bacterium which lives in the root nodules of leguminous plants. Rhizobium fixes atmospheric nitrogen into nitrogenous compounds.
• The bacteria and fungi present in soil decompose dead organic wastes of plants and animals, and convert them into manure. The manure contributes to the humus content of the soil, thereby helping in increasing its fertility.
• Not only these, microorganisms which are found in soil are also a part of many biogeochemical cycles which would not take place in their absence.

The above points explain the fact that how important microbes are and if they are destroyed its effect can be irreversible.

b. Vehicles and factories are the major sources of air pollution. If the number of vehicles and factories increase in our surroundings, it is obvious that it would result in increased levels of air pollution. Not only air pollution but they also result in noise pollution. In case, the no. of industries increase in our surrounding it means, more trees would have to be cut down to make way for them and thus resulting in damage to the environment.

c. If the total supply of potable water is finished then the life on earth will end. Water is required for the existence of living beings and in its absence, it owuld hamper their developemnt process and their survival.

Answer:

Answer:

(a) Constituents of the biosphere- hydrosphere and atmosphere
(b) Biotic constituents of soil- microorganisms and insects
(c) Fossil fuel- coal and petroleum
(d) Inert gases in air- oxygen and nitrogen
(e) Gases that are harmful to the ozone layer- carbon tetrachloride

Answer:

(a) Land and soil are the same thing.- False
(b) The water in a lake is called ground water.- Flase
(c) It takes about 1000 years to form a 25 cm thick layer of soil.-False
(d) Radon is used in decorative lights.- False

Answer:

a. Soil is formed by the process of weathering during which rocks break down to form soil particles. This breaking down of rock occurs over a period of millions of years. Weathering can be physical, chemical, and biological. The bedrock breaks down into pieces due to the effects of heat, cold, water, wind and rain. Microbes, insects and rodents also help iin this process. The roots of trees also help in the process of weathering.




b. Although water occupies about 71% of the earth's surface, all of it is not potable water. Most of the water is available in the form of seas and oceans which is salty in nature. This saline water has its limitations and cannot be used for many purposes. Around 2.7% of water exists in frozen state or as groundwater which is unaccessible. Only 0.3% of water is available as potable water which is fit for human consumption.

c.

• The importance of air can be understood by the fact that earth supports life becuase of the present of this air in our surrounding.
• It is required for various biological functions and biogeochemical cycles.

• All terrestrial organisms live on land.
• We use it for the purpose of land farming, building houses, roads etc.
• The plants and animals which we use also grow on the land.
• The minerals which we obtain from deep inside the earth are also important resources. For example, petrol, coal etc.

• Water plays an important role in various vital processes that are carried out by our body. All cellular processes take place in water medium.
• The availability of water plays an important role in deciding the number of individuals of each species that will be able to survive in a particular area, and also the sustainability of life in the region. 
• Fresh water is utilized by humans for consumption. 
• Water is central to the lives of aquatic animals which live in water.