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Among all the members of the solar system, only Earth has got suitable temperature, air and water required to sustain life.

Hint: CO₂ takes heat and does not allow it to escape into space. As a result, the average temperature of the earth’s atmosphere is gradually increasing.

The Right option is : (b) oxygen

There are two main divisions of biosphere : 

1. Living (Biotic)

2. Non-living (Abiotic). 

1. Living (Biotic): The biotic division includes human beings, vegetation, animals and minute insects. 

2. Non-living (Abiotic): The lithosphere, hydrosphere and atmosphere are included in the abiotic division.

Sound is heard only in the presence of atmosphere. Radio and television transmissions are possible only due to atmosphere.

Molten rocks in the interior of Earth are known as ‘Magma’.

The process of cooling of vapour is called ‘Condensation’. Various forms of moisture like dew, fog, clouds and precipitation, etc. are seen due to condensation.

There are four major spheres on Earth. They are :

1. Lithosphere

2. Hydrosphere

3. Atmosphere and

4. Biosphere.

Human activities like intense mining for minerals, underground nuclear testing, deep drilling to obtain mineral oil and tube wells etc. affect the lithosphere adversely.

Dust particles in the atmosphere spread sunlight in all directions. It is due to these particles that it does not suddenly turn dark after sunset and neither does it ‘ suddenly turn bright after sunrise.

Importance of lithosphere: 

The solid part on which we live is known as the lithosphere. ‘Litho’ means ‘Rock’ and ‘Sphere’ means ‘layer’. This layer occupies about 29 % of the surface of the Earth and is almost 64 km to 100 km thick. Landforms like mountains, plateaus, plains, valleys, etc. are seen on the lithosphere.

Lithosphere is useful in many ways. It is the home of mankind. It gives space for constructing homes, obtaining fresh water and land for cultivation as well as forests and useful minerals for industries.

Ozone gas is found in greater proportion in the morning in open grounds and in the air near the sea.

Ozone gas absorbs ultra-violet sunrays and saves the biosphere on Earth from their harmful effects.

Human activities affect the hydrosphere adversely:

1. Oil spills from ships and

2. Disposal of industrial and chemical waste into rivers, streams, ponds, lakes and seas pollutes the water and destroys marine life. This is highly dangerous for the hydrosphere.

3. Polar ice caps have started melting due to increasing heat.

The sphere of air that wraps the Earth from all sides is called ‘Atmosphere*. It extends up to about 1600 km from the surface of the Earth and it cannot be seen clearly with the naked eye.

Uses of atmosphere :

• Oxygen in the atmosphere is essential to all living organisms on the earth.
• Nitrogen is necessary for the growth of vegetation.
• Carbon dioxide is the food for green vegetation.
• Nitrogen reduces the intensity of oxygen.
• Ozone gas absorbs the ultra-violet sunrays and thus protects the earth from the intense heat’ of the sun. Ozone is also an invigorating gas.
• The dust particles in the atmosphere help to spread sunrays in all directions. So there is neither sudden light after sunrise nor sudden darkness after sunset. Dust particles reflect sunrays which help us to receive sunlight. These particles also help to form clouds.
• We can hear sound only due to the atmosphere. Radio broadcasts and television are possible only due to the presence of atmosphere.

The liquid component of Earth is called ‘Hydrosphere*. It includes oceans, seas, bays, straits, lakes, ponds, rivers, etc. The hydrosphere covers about 71 % of the Earth’s surface.

Uses of hydrosphere :

1. Hydrosphere provides us with fresh water.

2. Most of the rainwater comes from hydrosphere.

3. Valuable chemicals and minerals are obtained from seas and oceans.

4. A variety of aquatic life is sustained by oceans and seas.

5. Salt is produced from sea water.

6. The tremendous force of waves, tides and ocean currents is a potential source for generating electricity.

7. Oceans are also useful as waterways.

Earth was a huge ball of fire which cooled down with time. Various elements on Earth were transformed into solids, liquids, gases or life forms in the process. 

They formed the four major spheres on Earth, which are : 

(1) Lithosphere 

(2) Hydrosphere 

(3) Atmosphere 

(4) Biosphere. 

The elements on the surface of the Earth that got transformed into solid (land) make up the ‘Lithosphere’. Elements that got transformed into liquid form the ‘Hydrosphere’; those which transformed into gases are called the ‘Atmosphere’ and the living world which developed is known as the ‘Biosphere’.

a. Thekkini was flooded with water.

b. It had four wooden pillars.

c. Nalukettu is the central hall.

Puffed up appearance of dough is due to production of CO2 as a result of fermentation.

1. Fermentation

2. CO₂

(a) nitrogen gas

Carbon dioxide (CO₂) is an important gas in Earth's atmosphere but on the other hand if it is increased above certain limit then it is considered harmful especially for human beings. Air contains 0.04% carbon dioxide, 21% oxygen, 78% nitrogen. Other gases are present in very small quantities.

Correct answer is (b) southern

Solar Energy

Many scientist believe that solar energy is the future fuel. To cut down electricity bills, we should use solar energy. You can choose a full solar electrical system and completely remove yourself from the local power supply company. Solar systems can heat the water in your homes to fill your hot-water tank. Almost every electronic device that contains GPS or receives information via satellite such as cell phones, use some of the oldest solar technology around. Satellites that link us to most mass forms of media directly or indirectly use the sun’s rays to power them.

Wind Energy

The earth is a source of many forms of energy such as hydro, biomass, nuclear and geothermal. Wind energy is a source of energy which is free, very abundant and environment friendly. Wind turbines are one of the power generating devices, which utilize wind energy to generate power. This electricity is used to run electric devices and or stored in the batteries. Many countries use wind energy to power a pump water from the ground. The wind energy is also used to power the sailing ships in the sea. A more enjoyable use to wind energy is for sports and activities that rely on the power of wind.

Hydro Energy

Like wind energy, Hydro energy is mostly used for electricity generation and accounts for almost 20% of the total global electricity production. Hydro- power is also used to store energy. Hydro electricity is one of the cheapest and nonpolluting sources of power. It is much more reliable than wind and solar power. The most common type of hydro-electric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity.

(a) central hall

Correct answer is (c) innumerable

Correct answer is (a) slammed

Chlorofluorocarbons.

B. reduction in the emission of greenhouse gases 

Global warming has become a major concern for governments worldwide. Many countries have reached an agreement to control the situation by reducing the emission of greenhouse gases.

Ozone layer in the upper atmosphere prevents ultraviolet radiations of the sun from reaching the earth.

Several steps have been taken by Supreme court to protect Taj Mahal. The industries around Taj Mahal have been ordered to switch into clean fuels such as Compressed natural gas-CNG and Liquified petroleum gas- LPG. It has been advised that the automobiles should be switched over to unleaded petrol.

Carbon monoxide combines with the haemoglobin of our blood. It reduces the oxygen carrying capacity of blood.

Even the clear, transparent and odourless water may not always be safe for drinking because it may contain pollutants. These pollutants include the chemicals which may be discharged from the Industries such as oil refineries, paper factories, textile and sugar mills and chemical factories. These chemicals include arsenic, lead and flourides which are very toxic to human beings, plants and animals. These pollutants can also be chemicals used in farming such as pesticides and weedicides. All these chemicals dissolve in water and are washed into water bodies from the fields. They also seep into the ground and pollute ground water.

(b) frightening

Chlorination is a commonly used chemical method for purifying water.

(b) school bus

D. ultraviolet rays 

Chlorofluorocarbons used in refrigerators, air conditioners and aerosol sprays are responsible to deplete the ozone layer in the atmosphere. Ozone layer protects us from harmful ultraviolet rays of the sun.

(a) The source of Sulphur dioxide in the air is the fossil fuels combustion in the power plants and other industries. It can also be produced by the motor vehicles emissions.

Sulphur dioxide is a very harmful pollutant when present in the atmosphere. It can cause the respiratory problems, including permanent lung damage.

(b) The source of nitrogen dioxide in the air is produced by the motor vehicles. Nitrogen dioxide is a very harmful pollutant because it combines with other air pollutants and fog to form smog. The smog is responsible for causing breathing difficulties such as asthma, cough and wheezing in children.

(c) The source of carbon monoxide in the air is by the incomplete burning of fuels such as petrol and diesel. Carbon monoxide is a very poisonous gas which reduces the oxygen carrying capacity of blood.

(d) The Chlorofluorocarbons are used in the refrigerators, air conditioners and aerosol sprays. The Chlorofluorocarbons are responsible to deplete the ozone layer in the atmosphere. Ozone layer protects us from harmful ultraviolet rays of the sun. This results in increase of ultraviolet radiations at ground level which gives rise to an increased risk of skin cancer.

The various air pollutants discharged by motor vehicle exhausts are carbon dioxide, carbon monoxide, nitrogen oxides and smoke.

The harmful substances like sewage, toxic materials, silt etc., when gets mixed with water, causes water pollution. The pollutants which cause water pollution are: Chemical waste from industries, sewage, silt, agricultural chemicals and garbage thrown into water.

Water pollution can be controlled in the following ways:

1. Water should go through the sewage treatment plants before discharging into the water bodies. 

2. Use of pesticides and weedicides should be limited in order to prevent pollution. 

3. Industrial waste should be treated for harmful chemicals before discharging into the water bodies. Water treatment plants should be installed in all the industrial areas. 

4. We should save water consciously and should prevent the wastage of water. We must reuse, recycle and reduce the usage of water. We must try to reuse water. 

For example, water used for washing vegetables can be used to water plants in the garden.

Carbon monoxide interferes with haemoglobin. It is produced from incomplete combustion of fuels such as petrol and diesel. Carbon monoxide present in atmosphere tends to combine with Haemoglobin to produce carboxyhaemoglobin. It reduces oxygen carrying capacity of blood and leads to suffocation. Excess of carbon monoxide may even lead to death.

a) CO₂, Methane, Nitrous oxide

(i) sulphur dioxide

(ii) nitrogen dioxide

Toddy traditional drink made by fermenting the sugar sap extracted from palm plants and coconut palm.

C. carbon monoxide 

The air pollutants such as Sulphur dioxide and nitrogen dioxide which reacts with water vapors in the atmosphere to form sulphuric acid and nitric acid. These acids combine with rain and makes the rain water acidic. This is called Acid rain.

The industries such as oil refineries, rubber processing, automobiles and chemical industries have been responsible for the emission of air pollutants. These pollutants include Sulphur dioxide and nitrogen dioxide which reacts with water vapors in the atmosphere to form sulphuric acid and nitric acid. These acids combine with rain and makes the rainwater acidic. This is called Acid rain. 

Following are the harmful effects of acid rain:

Acid rain is very harmful for fish and other animals. It makes the water acidic and causes them to absorb the aluminum that makes its way from soil into lakes and streams.

Increased acidity of water due to acid rain adversely affects the growth and reproduction ability of fishes.

It damages buildings, monuments, and statues.

Acid rain is caused by two major air pollutants named sulphur dioxide and nitrogen dioxide. These gases react with water vapour present in atmosphere to form sulphuric acid and nitric acid respectively. These water vapours makes the rain acidic called 'acid rain’. Natural volcanic emissions, automobiles, factories burning coals etc. are responsible for acid rain.

Acid rain is caused by two major air pollutants named sulphur dioxide and nitrogen dioxide.

• Acid rain contaminates water and enters man’s body which may cause potential threat to human health.
• Many bacteria, aquatic organisms and blue-green algae are killed due to acidification which disturbs the whole ecological balance.
• Acidification of soil leads to reduced forest productivity.
• Acid rain causes extensive damage to buildings (e.g. - Taj Mahal) and material of marble, limestone, slate etc.

Greenhouse effect is Sun’s heat is trapped and not allowed to escape

b) Sulphur-dioxide and Nitrogen dioxide