Natural Resources : Previous Year's Questions



1 Mark Questions

 

Q.1 What is smog?                                                                    

[CBSE (CCE), 2012]

Smog is a combination of smoke and fog. This is formed due to the condensation of fog on the carbon particles present in the smoke that is produced due to the combustion of domestic fuels and industrial fuels like coal and petroleum. It lowers the visibility during the winter season and is an indication of air pollution.


Q.2  Name the free living nitrogen fixing bacteria.              

[CBSE (CCE), 2012]

Free-living (non-symbiotic) bacteria, cyanobacteria (or blue-green algae) Anabaena and Nostoc. Mutualistic (symbiotic) bacteria such as Rhizobium, associated with leguminous plants.


Q.3 State two factors responsible for weathering of rocks.                              

[CBSE (CCE), 2012]

Two factors responsible for weathering of rocks are: 

(a) Climate conditions- It includes the meteorological elements effect on rocks such as moisture, temperature, and wind and air pressure

(b) Topography and vegetation- Topography directly effects weathering by exposing rocks to the temperature or sun and wind. The elevated areas will be affected more and low level areas will be affected less

(c) Composition-There are certain elements which are included in rock composition. Some rocks will weather quickly and some slowly e.g. acidic rocks weather more quickly than basic ones. Surface covered by the vegetation are protected from weathering but bare surfaces are weathered to great extent. 


Q.4 Mention the two processes in which oxygen is used up from the atmosphere and the only process in which it is returned to the atmosphere.

[CBSE, 2011]

(i) Respiration and Combustion

(ii) Photosynthesis


Q.5 Write the two biotic components of the biosphere.             

[CBSE (CCE), 2011]

The biotic components of biosphere are plants, animals and microorganisms.


Q.6 How is CO2 fixed in the atmosphere?                                     

[CBSE (CCE), 2011]

It is fixed in many ways:

(a) During the process of respiration in humans and animals, carbon dioxide released into the atmosphere as a by-product

(b) Decomposition is the largest source through which carbon is returned to the atmosphere as carbon

(c) Weathering of rocks.

(d) By burning the fossil fuels

(e) From Volcanic eruptions

 

2 Marks Questions

 

Q.7 What is biosphere?                                                 

[CBSE, 2011]

The life-supporting zone of the earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible is known as the biosphere.  It accommodates several types of living organisms which remain dependent on natural resources. The biosphere ranges between 6km above sea level and 10km below sea level.


Q.8 Name two ways of preventing water pollution.                               

[CBSE (CCE), 2011]

(a) By using natural fertilizers and pesticides as far as possible, or if not, do not overuse them or over-water gardens and lawns. This will help in reducing the pollutants that get into water systems due to runoffs.

(b) Refrain from throwing litter into streams, lakes, rivers, seas or any water body.


Q.9 Name any four carbon containing molecules which are essential for living beings.

[CBSE, 2011]

(i) Nucleic acids (such as DNA, RNA)

(ii) Proteins

(iii) Lipids and

(iv) Carbohydrates


Q.10 Name the two gases given out by burning of fossil fuels, which dissolves in rain to form acid rain.

[NCT, 2008]

Sulphur dioxide (SO2) and oxides of nitrogen (NOx).


Q.11 State in brief the role of photosynthesis and respiration in carbon-cycle in nature.

[NCT, 2007]

The role of photosynthesis and respiration in Carbon cycle in nature are as follows:

(a) Plants convert the carbon inatmosphericcarbon dioxide into carbon-containing organic compounds, such as sugars, fats, and proteins.

(b) Cellularrespiration (in plants and animals)requires oxygen (which is the by-product of photosynthesis) and it produces carbon dioxide, which is used in photosynthesis.

In this way, photosynthesis and cellular respiration are linked in the carbon cycle.

 

3 Marks Questions

 

Q.12 What are the two forms of oxygen found in atmosphere? What is their importance?

[CBSE (CCE), 2012]

In atmosphere, oxygen is found as

Diatomic molecular form with chemical formula O 2 known as oxygen.

Triatomic molecular form with chemical formula O known as ozone.

The presence of oxygen in the air (atmosphere) is very essential for the following:

1. The life processes such as respiration, in all living organisms.

2. Combustion of fuels. Otherwise, fire would not have been possible

The presence of ozone in the air (atmosphere) is very essential for the following:

1. Ozone is a gas in the atmosphere that protects everything living on the Earth from harmful ultraviolet (UV) rays from the Sun.


Q.13 What is soil? How is it formed? State the major factors that decide the structure of a soil. What role does it play?          

[CBSE (CCE), 2012]

Soil is a mixture of broken rocks and minerals, living organisms, and decaying organic matter called humus. Humus is dark, soft and rich in nutrients. Soil also includes air and water.

Soil is formed by the following actions:

(a) Action of sun: The sun causes the heating of rocks during the day which causes them to expand. Then, these rocks cool down during night time leading to their contraction. Since, all parts of the rocks do not expand and contract at the same rate; it results in the formation of cracks on the rocks. Finally, these huge rocks break down into smaller pieces.

(b) Action of wind: Strong winds and storms also erode the rocks. The strong wind carries small rock pieces and sand from one place to another like water.

(c) Action of living organism: Roots of plants break down the rocks. Similarly, Lichens grow on the surface of rocks. These lichens release certain chemical that causes the rock surface to powder down to form a thin layer of soil.

(d) Action of water:  (i) Water gets into the cracks in the rocks, when this water freezes, it causes the cracks to widen. (ii) Flowing water wears away even hard rocks over long periods of time. Fast flowing water often carries big and small particles of rock downstream. These rocks rub against other rocks and the resultant abrasion causes the rocks to wear down into smaller and smaller particles, resulting in the formation of soil.

The type of soil is decided by the average size of particles found in it and the quality of the soil is decided by the amount of humus and the microscopic organisms found in it.

The nutrient content of a soil, the amount of humus present in it and the depth of the soil are some of the factors that decide which plants will thrive on that soil. The quality of the topsoil is an important factor that decides biodiversity in that area.


Q.14 Our earth is covered with approximately 75% water; still there is an urgent need to conserve water, why?                               

[CBSE (CCE), 2012]

Water covers nearly 75% of the earth but most of the earth’s water is salty or permanently frozen. Ninety - seven percent of all the water on the earth is salt water which is not suitable for drinking. Only three percent of all the water is fresh water, and only one percent is available for drinking water. The other two percent is locked in ice caps and glaciers. Fresh water is found in ice, lakes, rivers, streams and underground.

With all the people on Earth relying on such a small percentage of all the water on Earth, it only makes sense that we must preserve and conserve our water. Moreover, most of the sources of water supply are contaminated by industrial waste or sewage making it all the more necessary to conserve water.


Q.15 (a) What causes wind?                                                               

(b) List any two methods of preventing soil erosion.

[CBSE (CCE), 2012]

(a) The air above land gets heated faster and being light, it starts rising up. As the air rises, a region of low pressure is created. As a result, the air from the surrounding areas and from the top of the water bodies rushes into this area. The movement of air from one region to another creates wind.

(b) Soil erosion can be prevented by avoiding over-grazing, by constructing proper drainage canals around the fields.


Q.16 What is greenhouse effect? List two greenhouse gases. State the ultimate effect of increase in greenhouse gases in the environment.

[CBSE (CCE), 2012; MSE, 2004; KVS, 2007]

The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases thereby warming the Earth enough to support life.

Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs).

The rapid increase in greenhouse gas concentrations in the atmosphere has led to the enhanced greenhouse effect, which is when too much heat is trapped on Earth, resulting in an overall increase in global temperatures. Rising temperatures on Earth have produced severe changes in weather patterns, such as hotter summers, colder winters and stronger storms, like hurricanes and tornadoes. Increasing global temperature will also lead to a rise in sea levels as the glaciers and polar ice caps melt.


Q.17 (a) List two ways by which carbon dioxide is ‘fixed’ in the environment.

          [CBSE, 2012]

(b) Name two diseases caused due to an increased content of pollutants in the air produced due to the burning of fossil fuels.                  

[CBSE, 2011]

(a) Carbon dioxide is fixed in the two following ways:

(i) By the process of photosynthesis in plants.

(ii) Many marine animals use carbonates dissolved in sea-water to make their cells.

(b) Diseases caused due to an increased content of pollutants in the air produced due to the burning of fossil fuels are- ophthalmic problems, skin injuries, gastro-intestinal, cardio-vascular and respiratory diseases and some types of cancer.


Q.18 What is the role of the atmosphere in climate control?

[CBSE, 2011]

The atmosphere plays an important role in temperature control. Atmosphere covers the Earth, like a blanket. Air is a bad conductor of heat. The atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the course of the whole year. It also prevents the sudden increase in temperature during the daylight hours. Moreover, during the night, it slows down the escape of heat into outer space.

 

5 Marks Questions

 

Q.19 (a) What are the consequences of Global warming?

(b) Draw a labelled diagram to show water cycle in nature.

(c) Why is water essential to life?                               

[CBSE (CCE), 2012]

(a) Harmful effects of global warming:

(i) Warmer waters and more hurricanes:As the temperature of oceans rises, so will the probability of more frequent and stronger hurricanes.

(ii) Increased probability and intensity of droughts and heat waves: Although some areas of Earth will become wetter due to global warming, other areas will suffer serious droughts and heat waves.

(iii) Polar ice caps melting: The ice caps melting are a four-pronged danger. It will raise sea levels.

(iv) More floods:Flooding represents one of the most dangerous hazards to human settlements and As the climate changes, a warming of the seas creates ‘thermal expansion’. This is where warm water begins to take up more space than cool water, making the sea’s surface level increase.

(b)

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(c) Organisms need water because it plays a vital role in the reaction that takes place within organism’s cells and body. It acts as a universal solvent, providing a medium for the chemical reactions to occur. Substances are also transported from one part of the body to the other in dissolved state. Therefore, it is not necessary for organisms to maintain a distinct level of water within their bodies to  stay alive.


Q.20 (a) What makes biosphere dynamic but stable system?

(b) Draw a labelled diagram to show the oxygen cycle in nature.

[CBSE (CCE), 2012]

(a) Biosphere has biotic (living) and abiotic (non-living) components. The biotic or living components include plants, animals and microbes living on the earth. Abiotic components are land water and air. A constant interaction between the abiotic and biotic components of the biosphere results in the transfer of food and energy, which makes it a dynamic but stable system.

(b) Oxygen cycle in Nature: -


Q.21 (a) Difference between biodegradable and non biodegradable substances.

(b) How is acid rain causing harm to Taj Mahal?

(c) What is smog?                                                          

[CBSE (CCE), 2011]

(a) Biodegradable and non-biodegradable substances-

(b) Taj Mahal is situated in Agra. The air in this place contains serious levels of sulphur and nitrogen oxides. This is due to the large number of power plants and industries set up around this area. All these led to acid rain. Acid rain reacted with the marble (calcium carbonate) of Taj Mahal and makes it yellow in colour. 

(c) Smog is a combination of smoke and fog. This is formed due to the condensation of fog on the carbon particles present in the smoke that is produced due to the combustion of domestic fuels and industrial fuels like coal and petroleum. It lowers the visibility during the winter season and is an indication of air pollution.


Q.22 (a) What is soil erosion? Give two methods of reducing it.

(b) Name two biologically important compounds that contain both oxygen and nitrogen.

(c) Why is water essential for life?                              

[MSE, 2008]

(a) The top layer of the soil that contains humus and living organisms in addition to the minerals is called the Topsoil. The removal and thinning of the fertile topsoil from its original place to another place with the help of certain agents such as strong winds, running water etc is called soil erosion.

Methods of reducing soil erosion-

  • By constructing proper drainage canals around the fields.
  • Intensive cropping and maintain soil fertility.

(b) Two biologically important compounds that contain both oxygen and nitrogen are

Proteins (their basic units are amino acids which are made up of an amino group with nitrogen and a carboxylic acid with oxygen in them)

Nucleic acids- both DNA and RNA are compounds with a ribose and phosphate groups with oxygen and the nitrogen bases with nitrogen

(c) Organisms need water because it plays a vital role in the reaction that takes place within organism’s cells and body. It acts as a universal solvent, providing a medium for the chemical reactions to occur. Substances are also transported from one part of the body to the other in dissolved state. Therefore, it is not necessary for organisms to maintain a distinct level of water within their bodies to stay alive. Moreover, we need water for many activities such as drinking, cooking, washing, agriculture, etc.



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