Pollution and Pollutants Class 6 ICSE — Biology Chapter 9

This pollution and pollutants class 6 ICSE chapter is the ninth chapter in the Biology textbook. It defines pollution and pollutants, and explains the four major kinds — air, water, soil and noise — with their causes, effects and prevention. The chapter also covers the greenhouse effect and global warming. It ends with the conservation of resources such as water, forests, coal and petroleum.

Download Pollution and Pollutants Class 6 ICSE Biology Chapter 9 PDF

Download the Pollution and Pollutants Class 6 ICSE Biology chapter PDF to revise offline or print for practice. It is the full chapter as printed in the book — 11 pages, 20 sections, 11 questions.

What is inside Chapter 9

11 pages · 20 sections · 11 exercise questions

• REVIEW QUESTIONS: 11 questions

1 POLLUTION AND POLLUTANTS

Chapter 9 opens with the syllabus for this ICSE chapter. It asks you to study the different kinds of pollution, and for each kind, its causes, effects and prevention. The syllabus also covers the need to conserve all kinds of resources. It suggests ways individuals can practise conservation in daily life, such as saving energy, fuels and water.

The chapter then lists four ways human activity damages the environment. Sewage and industrial waste are discharged into rivers, lakes and seas. Pesticides and fertilizers from farms wash into ponds and rivers with rain. Burning fossil fuels releases poisonous gases into the air. High-intensity sounds come from noisy buses, trucks, cars, loudspeakers and jet planes.

Two activities support this chapter. The first is collecting magazine and newspaper clippings about pollution and conservation, and making a bulletin board. The second is finding out about the greenhouse effect. You can verify the full syllabus on the official CISCE website.

2 Pollution and Pollutant

Pollution is the addition of any constituent to air, water or soil that changes the natural quality of the environment. The constituent that is added is called a pollutant. These two terms are easy to swap, and that is a common mistake in exams.

The chapter introduces a key idea: the dose of a pollutant decides the damage. Pour two litres of warm water from a kettle into a pond, and the pond hardly changes. Let a factory drain warm water at the same temperature for a full day, and the pond warms enough to disturb the fish and plants in it. In that example, heat is the pollutant.

Sewage works the same way. A small amount of sewage acts as a good fertilizer. Too much of it spreads infection and can create epidemics. The same substance is harmless, helpful or harmful depending on how much of it is present. This Class 6 ICSE chapter teaches that idea through the hot water contrast.

3 MAJOR KINDS OF POLLUTION

The chapter covers four major kinds of pollution:

• Air pollution
• Water pollution
• Soil pollution
• Noise pollution

A simple mnemonic to keep the order is AWSN — Air, Water, Soil, Noise. The comparison table below shows how each kind differs across causes, effects and prevention.

4 AIR POLLUTION

Air pollution comes from harmful gases, dust and smoke. The sources are factories, motor vehicles, and the burning of fuels such as coal and wood.

Two harmful pollutants get special attention: sulphur dioxide and the oxides of nitrogen. During rain, these form acids. That is how acid rain begins.

These gases also affect the earth’s temperature. They do not allow the heat of the earth to reflect back into space, while sunlight continues to fall on the earth. Because of this, the temperature of the earth is rising. The chapter names this the greenhouse effect, and notes that these gases cause global warming. The next section explains the greenhouse effect in detail.

5 Green House Effect

The greenhouse effect is the phenomenon in which the earth’s atmosphere traps the heat of sunlight reflected from the earth’s surface. The atmosphere acts like a glasshouse. Sunlight enters through the transparent glass, but the heat cannot escape. The temperature inside rises. In very cold areas, this method is used to grow plants.

The chapter explains why the blanket of gases is growing. Burning fuels such as oil, petrol and coal produces carbon dioxide. Plants use this carbon dioxide to make food, and release oxygen in return. Animals use that oxygen for respiration. But human activities produce more carbon dioxide than plants can use. Forests are being cut down for housing and industries. Carbon monoxide and methane add to the blanket in the same way.

The greenhouse effect is natural and useful. The problem is the human-made rise in carbon dioxide. That rise traps more heat, and the gradual warming of the earth’s atmosphere is called global warming. It is disturbing the whole system that maintains the earth’s climate.

6 Effects of Air Pollution

Air pollution has two main effects on people. The first is respiratory disease. Asthma, bronchitis and lung cancer are the examples given in the chapter.

The second effect is smog. Smog means smoke plus fog. It irritates the eyes and creates breathing problems. It also reduces visibility at night.

A common mistake is to treat smog as ordinary fog. The word is a blend of smoke and fog, and both parts matter.

7 Prevention of Air Pollution

The chapter gives five everyday measures a student can take:

• Use public transport instead of a single private vehicle.
• Get the pollution level of your vehicle checked regularly.
• Walk or use a bicycle for shorter distances.
• Shop from your nearby area so you do not need a vehicle.
• Install a CNG system in your vehicle.

Each measure is simple and within reach of an individual. Small daily choices reduce the total pollution from vehicles.

8 WATER POLLUTION

Water pollution is the addition of unwanted and harmful chemical substances into water bodies. The sources given in this ICSE chapter are sewage, industrial runoff, pesticides, fertilizers and garbage.

When water gets polluted, its physical and chemical properties change. The chapter reminds us that life is impossible without water, so we should not throw pollutants directly into water bodies.

9 EFFECTS OF WATER POLLUTION

Water pollution has three harmful effects. First, it causes the growth of micro-organisms that spread water-borne diseases. The diseases named are cholera, typhoid, jaundice and dysentery.

Second, it reduces the oxygen available to marine life such as fish. Third, harmful substances like lead and mercury enter the human body through the food chain. A fish from polluted water carries these substances, and a person who eats the fish takes them in.

10 Prevention of Water Pollution

The chapter lists four measures to prevent water pollution:

• Do not throw wastes directly into water bodies.
• Stop people and animals defecating near water sources.
• Treat industrial effluents before discharging them into water.
• Do not overuse pesticides and fertilizers, so they do not run off into nearby water.

Water and air pollution are very common, the chapter notes, and both cause direct harm to our lives.

11 SOIL POLLUTION

Soil pollution comes from two kinds of pollutants. The first kind is pollutants washed out of the atmosphere, as by acid rain. The second kind is insecticides and fertilizers used in agriculture.

Both kinds do the same damage. They alter the basic structure of the soil. They kill the minute organisms living in it. And they reach the human body through crops grown in such fields.

12 Effects of Soil Pollution

The causes of soil pollution include acid rain, chemicals, fertilizers, insecticides, pesticides and city garbage.

These substances kill the micro-organisms in the soil. Those micro-organisms normally maintain soil fertility. When they die, the soil loses fertility. Crops grown in polluted soil can be adulterated, and eating them affects human health.

13 NOISE POLLUTION

Noise pollution means unwanted sound. The sources named in the chapter are noisy vehicles such as buses, trucks and cars, loudspeakers, music systems, televisions and jet planes. High-intensity sounds are harmful to man.

The chapter gives the sound levels of common sources:

Reading the table from top to bottom shows the scale of sound. Silence sits at 0 decibels. A rocket engine sits at 180 decibels, the loudest entry. The gap between the quietest and loudest is 180 decibels.

14 Effects of Noise Pollution

Noise pollution has three effects on people. It reduces concentration on work. It reduces hearing efficiency. And it causes headache.

15 Prevention of Noise Pollution

The chapter gives three measures to prevent noise pollution:

• Play radios, televisions and stereos at low volume.
• Close your doors if the outside noise is not under your control.
• Do not scream; speak in a soft voice.

This section is followed by Activity 1 in the book. In it, you prepare a list of sources of air, water and noise pollution in your city or town, using the format given in the textbook.

16 HOW TO CONTROL POLLUTION ?

Pollution is a serious problem of the modern age, the chapter states. With rapidly increasing industries, the problem needs prompt attention. The chapter gives eleven measures to control various forms of pollution:

1. Install special devices such as precipitators in factories to remove harmful particles and poisonous gases from fumes.
2. Control automobile exhausts so vehicles do not release unburnt fuels. Delhi carries out compulsory checks on exhaust fumes.
3. Use safer fuels. CNG has been introduced in Delhi for city transport, and the Metro rail system runs on electric power.
4. Plant trees on a large scale along roadsides and elsewhere, a practice called social forestry.
5. Clean all effluents before releasing them, and detoxify pollutants before dumping.
6. Treat sewage fully before releasing it into rivers or fields.
7. Prohibit blowing of horns near schools and hospitals.
8. Protect yourself personally by holding hands over ears, or using cotton or ear plugs.
9. Avoid wasting water.
10. Avoid using polythene bags.
11. Use public transport or pool cars.

This ICSE chapter frames these as the responsibility of both industries and individuals. Some measures are for factories, and some are for daily life.

17 VAN MAHOTSAVA

Van Mahotsava is India’s massive tree plantation programme. Its purpose is to reduce pollution and improve the overall quality of the environment. Every year at the beginning of the rainy season, thousands of new saplings are planted to promote forestry.

Van Mahotsava connects directly to the social forestry idea from the previous section. Tree plantation along roadsides and elsewhere reduces air pollution, and a national festival of planting multiplies that effect.

18 CONSERVATION OF RESOURCES

The chapter explains that demands on resources have risen continuously in recent decades. Four factors drive the increase: growth in population, advancement of industrialization, a rise in the standard of living, and high expectations for a better life. Over-consumption depletes resources, pollutes them, and can exhaust them.

Conservation of soil fertility comes first. The topmost layer of the land is the most fertile and best suited for plant growth. It can be preserved in two ways: prevent soil erosion, and restore fertility with natural fertilizers and manures.

Conservation of water comes second. If the water taken out through tubewells equals the water replenished by rain, the water level stays constant. Problems arise when more water is taken out than rain water returns to the soil. Rapid population growth adds further demand, and the chapter notes this has caused water shortage in many parts of the world.

19 Steps to conserve water

Conservation of water starts with five steps. Build dams and reservoirs to store river and rain water for dry periods. Build tanks and ponds to retain rain water, a form of water harvesting. Reforest hill slopes and catchment areas to hold rain water back and prevent loss in floods.

Recharge the water table through rain water harvesting — collecting or trapping water from nature and putting it to use. One domestic method is to channel the water that runs off roofs into collection tanks. Mass awareness programmes promote the judicious use of water.

Conservation of forests uses three steps: use alternative energy such as biogas and solar energy, discourage grazing of cattle in forests, and launch wide-scale reforestation.

Conservation of wildlife needs three steps. Conserve natural habitats, since different species require different habitats. Ban hunting of endangered species like the lion, tiger, peacock and bustard. Develop national parks and wildlife sanctuaries, such as Jim Corbett National Park, Kanha National Park, Gir Forest, Kaziranga and the Ghana Sanctuary in Bharatpur.

Coal and petroleum are fossil fuels. Coal formed from vegetable matter buried under the earth about 300 million years ago. Dense forests died, decayed, and were submerged under water, then covered with sand and clay. Pressure and temperature converted the matter into coal.

A fossil is any remains or impression of a living being of past geological ages preserved in the earth’s crust. Coal deposits are limited and will never be produced again, so coal is a non-renewable source of energy.

Petroleum formed from the remains of animals and plants buried under the sea millions of years ago. In its natural form it is a thick black liquid called crude oil. Distillation of crude petroleum gives six products:

• Petroleum gas, used as a fuel or as LPG.
• Petrol, used as fuel in motor vehicles.
• Kerosene, used as a household fuel.
• Diesel, used in heavy vehicles.
• Lubricating oil, used as a lubricant.
• Paraffin wax, used for vaseline, ointments and candles.

A mnemonic for the six products is the initials GPKDLW — gas, petrol, kerosene, diesel, lubricant, wax. CNG is an almost pollution-free fuel. Coal and petroleum are exhaustible and non-renewable. At current rates, petroleum may last a couple of centuries and coal a few more. The chapter urges replacement with wind, solar, tidal and geothermal energy. Biogas helps prolong the supply. The theme of conservation runs through the whole Class 6 books collection on this site.

20 SCIENTIFIC TERMS TO REMEMBER

At the end of the book, the glossary lists scientific terms used across all chapters. From that list, the terms that belong to this chapter are:

What to practise from Pollution and Pollutants Class 6 ICSE

The practice blocks in this chapter are:

• REVIEW QUESTIONS — 11 questions covering the whole chapter.
• ACTIVITY 1 — prepare a list of sources of air, water and noise pollution in your city or town.
• ACTIVITY 2 — collect news clippings about pollution or conservation efforts, paste them in a scrapbook, and discuss them with classmates.

The review questions follow an exam pattern. They ask you to define a term, list effects, or give a prevention measure. Examples include the definition of pollution, prevention of air pollution, the greenhouse effect, the meaning of smog, three harmful effects of water pollution, why coal is a fossil fuel, and the ill-effects of noise pollution. Practise answering in that three-part shape. In the pollution and pollutants Class 6 ICSE chapter, every section follows the same structure: cause, effect, prevention.

Other chapters in this subject are listed on the Class 6 Biology books page.

Pollution and Pollutants Class 6 ICSE frequently asked questions

What are pollution and pollutants in Class 6 ICSE Biology?

Pollution is the addition of a constituent to air, water or soil that changes the natural quality of the environment. A pollutant is that added constituent. The chapter covers the four kinds of pollution — air, water, soil and noise — with causes, effects and prevention, and ends with conservation of resources.

What is the difference between pollution and a pollutant?

Pollution is the process of adding a harmful constituent to the environment. A pollutant is the constituent itself. In the hot water example, heat is the pollutant, and the warming of the river is the pollution.

How does the greenhouse effect cause global warming in this ICSE chapter?

Burning fuels produces carbon dioxide, and carbon monoxide and methane add to the blanket of gases. Forests that absorb carbon dioxide are being cut down. The blanket traps heat reflected from the earth’s surface, so the atmosphere warms gradually. That gradual warming is global warming.

Why is coal a fossil fuel and a non renewable source of energy in Class 6 ICSE?

Coal formed from vegetable matter buried under the earth about 300 million years ago. A fossil is any remains of a living being of past geological ages preserved in the earth’s crust. Coal deposits are limited and will never be produced again once finished, so it is non-renewable.

Which diseases can water pollution cause in this ICSE chapter?

Water pollution causes water-borne diseases such as cholera, typhoid, jaundice and dysentery. These are spread by micro-organisms that grow in polluted water.

Reference: ICSE Class 6 Biology textbook material, chapter 9: Pollution and Pollutants — CISCE-aligned.