CBSE Class 9 Science Natural Resource Worksheet Set 03

 

Answer : CFCs are chlorofluorocarbons are man-made organo-halogens used in refrigerators that degrade the ozone layer.

 

Answer : It is used for human consumption and irrigation.

 

Answer : The resources that are available in limited quantity and get depleted if wise use is not done.

 

Answer : The thinning of ozone layer at few places is called ozone hole.

 

Answer : Photosynthesis and respiration.

 

Question : What are the different states in which water is found during the water cycle?
Answer : During the water cycle, water is found in solid state (snow, ice. etc.), liquid state (ground water, river water, etc.) and gaseous state (water vapours).

 

Short / Long Answer

 

Question : List any three human activities which would lead to an increase in the carbon dioxide content of air.
Answer : The human activities which would lead to an increase in CO₂ content of air are;
Deforestation increases the level of CO₂ in the environment.
Respiration is the natural way to release of CO2 by plants. It is balanced by the release of oxygen by plants. So, it is not harmful for the environment.
Combustion of Fuels leads to increase in CO2 level in the atmosphere.
Fuels are burnt to carryout activities like cooking, transportation and in industrial processes.

Question : What are the two forms of oxygen found in the atmosphere?
Answer : The two forms of oxygen found in the atmosphere are;
Elemental oxygen is normally found in the form of diatomic molecule (O₂) in the lower part of atmosphere. It is about 21% in the air and nonpoisonous.
Ozone is found in the stratosphere part of atmosphere. It contains three atoms of oxygen (O₃).

Question : Why is the atmosphere essential for life?
Answer : Atmosphere is essential for life due to following reasons:
It maintains the appropriate climate for the sustain of life 
It keeps the average temperature of the Earth steady during the day and even throughout the year.
It prevents the sudden increases in temperature during the daylight hours.
The gases it contains are required for sustaining life on Earth. These gases are:
o Oxygen , Carbon dioxide and Nitrogen
A thick layer of ozone (in stratosphere) of atmosphere filters the harmful UV radiations reaching the Earth. The UV rays produce harmful effects on all living organisms.

Question 3:How are living organisms dependent on soil? Are organisms that live in water totally independent of soil as a resource?
Answer : Living organisms depend on soil in the following ways:
Soil helps to bind the roots of plants to provide them anchorage. The nutrients in soil are absorbed by the plants for their growth and development.
It provides natural habitat for various living organisms, e.g., bacteria, fungi, algae, earthworms, etc. These help to maintain the fertility of soil.
Many animals like rats, rabbits, etc., make their home in the soil.
Earthworm performs all its activities in the soil. It maintains the fertility of soil by releasing nitrogen rich excreta.
Organisms that live in water are not totally independent of soil as a resource. These organisms depend on aquatic plants for food and other substances These aquatic plants in turn require minerals for their sustenance These minerals are carried to water bodies from soil by rivers, rain water, etc. without the supply of minerals from the soil to the water bodies, it is impossible to imagine aquatic life.

Question : We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and Limited areas would help in reducing pollution?
Answer : Yes. Isolating human activities to specific areas would help in reducing levels of pollution. For example, setting up of industries in isolated regions will control pollution to some extent. The pollution caused by these industries will not contaminate water resources, agriculture land, fertile land, etc.