ICSE Class 8 Biology Chapter 09 Pollution and Conservation

Pollution And Conservation

Syllabus

1. Understanding the terms: renewable and non-renewable resources, biodegradable and non-biodegradable materials, conservation, deforestation, afforestation, corrosion, contamination, pollution.

2. Ways in which pollution can affect air, water and soil - steps to be taken to preserve these resources.

3. Deforestation and depletion of wildlife - upsetting the balance of nature - how it affects Man - what steps need to be taken to prevent/reduce these.

4. Fossil fuels - alternative sources of energy - briefly.

5. Setting personal goals and practising methods of reducing pollution and conserving energy and materials.

- Identifying local problems of air, water and noise pollution and steps to be taken to reduce the same.

- Practising small but significant changes in life style through participation in campaigns at school, home and outside E.g. "Say NO" to plastic", Save water, Switch off electrical appliances when not in use, to save electricity), setting up compost pits in gardens, collecting garbage, recycling materials, creating useful products from waste etc.

- Experiments to find out how long, different materials take to get degraded in a compost heap; which ones do not get degraded etc. (E).

Introduction To Natural Resources

Human beings have always been utilising air, water, plants and animals for their survival. With the progress of civilisation, their needs increased and became more varied.

With the coming up of industries, man started extracting various minerals and metals from the earth. With the technological advancement, the needs went on increasing and the human beings started obtaining more and more from nature and using it for their benefit.

Because of ever increasing human population, large scale urbanisation and industrialisation, humans have been exploring materials which they utilise for their maintenance and welfare. Such materials of use are called resources or more commonly, natural resources.

Natural resources are those materials that have been created by natural processes or in other words, we can say that they are resources (or things of use) that nature has provided us.

Teacher's Note

Every glass of water you drink and every breath of air you take are gifts from nature - understanding where they come from helps us appreciate and protect them better.

Classification Of Natural Resources

Natural resources can be classified into two major categories depending on the extent of their availability:

1. Inexhaustible resources: They are unlimited in quantity, and are not likely to be finished or exhausted.

Examples: Air, water and solar radiation.

2. Exhaustible resources: They are limited in quantity, and are likely to be finished forever or exhausted.

The exhaustible resources can be further classified into two sub-categories:

(a) Renewable resources:

- Once finished, these resources can regenerate or replenish themselves by recycling in a reasonable time.

- They are not likely to be exhausted.

Examples: Soil, forests, flora and fauna.

(b) Non-renewable resources:

- Once finished, these resources cannot regenerate or replenish themselves by recycling.

- They may finish forever.

Examples: Minerals and fossil fuels like coal and petroleum.

Some renewable resources, like ground water, forests and wildlife, if not managed properly, can become non-renewable.

Teacher's Note

When you plant a tree, it can grow back, but when you burn coal, it's gone forever - this is why some resources are renewable and others are not.

Pollution

Pollution is the degradation of environmental air, water and land with wastes from human activities. In earlier times, the human population was very small and people used to live a simple life. There were hardly any factories as well as vehicles. The industrial revolution, the growth of cities, advanced technology and the widespread use of vehicles are contributing lot of pollution to the environment.

To understand the phenomenon of pollution, let us take an example. If we pour a glass of hot water into a river, it would hardly affect the quality of water and the organisms living in it. But if we continuously drain hot water from a factory into the river, the river water would get heated to an extent that it would disturb and may destroy the aquatic plants and animals. In this situation, we can say that river water has become polluted. In this example, heat is the pollutant.

Some major polluting factors are:

1. Smoke from factory chimneys.

2. Industrial wastes discharged into rivers, ponds or the sea (water bodies).

3. Agricultural chemicals polluting the water bodies as well as the soil.

4. Exhaust fumes from automobiles.

5. Radioactive substances.

6. Oil spills.

7. Sewage discharged into lakes and rivers.

8. Loud noise and music.

Categories Of Pollutants

Substances which we come across in our daily life, if not taken care properly, can pollute our homes and surroundings. They can be classified into two kinds:

1. Biodegradable

2. Non-biodegradable

Biodegradable substances are those which can be easily broken down by biological agents (e.g. microorganisms). These include kitchen wastes, waste paper, residual food items, crop residues, etc. If managed properly, they can be turned into useful resources.

Non-biodegradable are those which can not be broken down by biological agents. For example, glass, aluminium, plastics, etc.

Teacher's Note

When you throw away a banana peel, it naturally decomposes in weeks, but a plastic bag will sit in a landfill for hundreds of years - knowing this difference helps you make better choices about what you use.

How Grave Can Be A Pollutant - An Example Of Carbon Dioxide

All animals give out carbon dioxide as a product of respiration, but most of this gas is used up by the green plants in producing their food during photosynthesis. But, look at the two situations.

- Factory chimneys throughout the world are pouring out huge quantities of carbon dioxide day and night in the environment. Apart from these, the discharges from automobiles, thermal power houses, etc. are the other major sources of carbon dioxide.

- Forests which used to absorb a greater part of the atmospheric carbon dioxide, have been mercilessly cut down by man.

- Due to two extreme conditions, the production of carbon dioxide has increased and the utilisation or absorption has decreased. Thus, carbon dioxide is now playing the role of a pollutant.

Major Kinds Of Pollution

There are five major kinds of pollution:

1. Air pollution 2. Water pollution

3. Soil pollution 4. Thermal pollution

5. Noise pollution.

Air Pollution

Air pollution is a grave problem, particularly for people living in large congested industrialised cities. The air above such places is heavily laden with dust, smoke, poisonous gases, solid impurities and offensive odours. These can be grouped under two categories:

A. Particulate pollutants. These include unburnt particles of coal or coke which are the main constituents of smoke, and particles from abrasive materials which are given out from the brake-linings of motor vehicles.

B. Gaseous pollutants. These include a variety of gases mostly given out during the burning of coal and oil during the industrial processes. These gases are mainly emitted in the form of sulphur dioxide, nitrogen dioxide, hydrogen sulphide, carbon monoxide, ammonia, etc. Efforts are being made to replace the conventional fuel - petrol and diesel - in automobiles with much less polluting CNG (Compressed Natural Gas) fuel.

Harmful Effects Of Air Pollution

The air pollution affects human life directly as well as indirectly. Some of its effects are given:

(1) Direct inhalation of particulate matter and poisonous gases affect human health in many ways.

High quantities of smoke and other particles may cause lung diseases, including lung cancer.

Sulphur dioxide (SO2), in particular, causes serious damage to the respiratory system.

Acid Rain

The oxides of sulphur and nitrogen released into the air, damage the environment in yet another way. They combine with rain water to form sulphuric and nitric acids and come down as acid rain. Acid rain harms plants, affects soil fertility, and even corrodes buildings. You must have heard that the marble of Taj Mahal at Agra is getting corroded by acid rain. It is due to the release of sulphur dioxide gas from nearby factories e.g., Mathura Oil Refinery etc.

Carbon monoxide (CO) is highly poisonous. It makes a stable compound with haemoglobin in the human blood. Its inhalation in large quantity, as from burning coal in a small closed room or from the exhaust of motor vehicles specially in a closed garage, may lead to death. When inhaled in small quantities, it leads to headaches and nausea.

(2) Indirect effects of air pollution on human life includes damage to trees, crops, clothes, rubber-tubing and buildings.

- A thick cloud of smoke may prevent sun rays to enter houses and other dwellings and the germs of many diseases may not be killed.

- Many plants and vegetables show poor growth in the presence of poisonous gases.

- Sulphur dioxide is causing much damage to the buildings. It combines with water vapours to produce sulphuric acid which corrodes metals and marble.

- "Acid rain" is the result of gaseous pollutants (chiefly, sulphur dioxide and nitrogen oxides), that cause much damage to plants and other organisms.

Measures To Control Air Pollution

The following measures may be adopted to control air pollution:

(1) Special devices such as precipitators should be installed in factories to remove particles and poisonous gases from the fumes before releasing them into the atmosphere.

(2) Controlling automobile exhausts. Steps should be taken to ensure that automobiles do not release unburnt fuels from their exhausts. Nowadays, a cheap and non-polluting fuel CNG is being used in all types of automobiles.

(3) Safer fuels. Use of coal and other fossil fuels should be replaced by the use of electricity, or other sources of energy.

(4) Tree plantation. The more the greenery, the less the pollution. Large scale tree plantation (social forestry) along roadsides and elsewhere in cities and towns reduces air pollution.

Teacher's Note

Planting trees along busy roads helps clean the air we breathe, just like how your lungs filter the air you inhale - nature has its own air purification system.

Water Pollution

The pollution of fresh water streams, rivers and lakes is caused by different kinds of domestic and industrial wastes poured into them (effluents). The water pollutants may consist of organic materials (dead remains of animals and plants), synthetic detergents, acids, alkalis and a variety of soluble salts.

Some of the river and pond water pollutants and their effects on human life are as follows:

(1) Organic pollutants lead to bacterial growth which reduces the amount of oxygen dissolved in water and, this in turn, kills the fish and destroys the aquatic life.

(2) Poisonous insecticides such as DDT and some industrial wastes containing mercury flow into water bodies. There, they are picked up by microscopic plants through which they enter the food chain and may ultimately reach fishes, and in turn, get into humans. These are highly injurious.

(3) Sewage is a major source of water pollution. Many cities still continue to pour their sewage directly into rivers, without treating it. This poses health hazards (causing diseases like cholera, typhoid, etc.).

Marine pollution is equally serious. Various kinds of industrial wastes are disposed off into the sea. The accidents of oil tankers in sea spread over large areas of water killing thousands of fishes.

Measures To Control Water Pollution

(i) All types of waste and effluents should be treated before they are released into water bodies. The pollutants should be detoxified before being dumped.

(ii) The sewage should be fully treated before releasing it into rivers or fields.

Teacher's Note

Every time you wash your hands and watch the water go down the drain, it's heading to rivers and oceans - treating this water properly protects the fish and plants that depend on it.

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