TNPSC Scicence Notes: 6th Standard: Biology: Our Environment

TNPSC 6th Standard - General Science Notes 

TNPSC Notes for Group 4 Exam

Biology: Our Environment 

Air, light, land, soil, water bodies, plants and animals around us constitute our environment. Environment is polluted, due to industrial development, over population, modern life style and urbanization, which leads to undesirable and harmful effects.


Unwanted substances formed during a process or substances which cannot be reused are called wastes or effluents.

Garbage are generated in places like houses, classrooms, industries and public places like streets, market and sea shore.

Types of garbage

Solid wastes which pollute environment are of two types, namely 

· Bio degradable waste

· Non bio degradable waste

Bio degradable waste

· Bio-degradable waste In nature, some wastes are gradually degraded by bacteria, fungi (micro-organisms) and earthworm.These are bio degradable waste. 

· Leaves, agricultural wastes, animal wastes, vegetables, fruits and their peel, seed, nut are examples of bio degradable waste.

Non bio degradable waste

· Non-biodegradable waste Waste substances that are not degraded by micro-organisms are non-biodegradable wastes. 

· Eg: plastics, industrial effluents, metals.

Disposal of garbage

If the wastes are not handled properly, they get accumulated besides occupying the land, they even cause bad odour and become abode of micro-organisms that cause diseases. 

Thus, people living such area are affected with various diseases. Therefore, it is a must dispose the garbage properly. 

It is a must to dispose the garbage properly. 

The following methods are used to dispose the wastes.

1. Landfilling

2. Incineration

3. Composting

4. Reducing the usage

5. Reusing

6. Recycling 

1. Landfilling 

Landfilling is a method in which wastes are dumped into naturally occurring or man-made pits and covered with soil. Garbage buried inside landfills remain here for a long time as they decompose very slowly and become manure. These places can be converted into parks, gardens, etc.

2. Incineration

The burning of solid waste in incinerator is called Incineration. Human anatomical wastes and bio-medical wastes (discarded medicines, toxic drugs, blood, pus) are disposed by means of incineration. During incineration, the enormous heat kills all contagious disease-causing germs.

3. Composting

The process of degradation of organic wastes into manure by the action of microorganisms is called composting. The manure thus obtained becomes natural fertilizer for the plants as well as increases the soil fertility.

Dried leaves, woody materials + fodder, food scraps = compost

4. Reducing the usage

The best way to manage wastes is not to produce them. This can be done by using durable goods that last longer instead of things that are used once and thrown away. Use of fountain pen in place of ballpoint pen is a good example of reduce.

5. Reusing

Reusing means using a thing again and again, rather than using and throwing it after a single use. Instead of using plastic bags for shopping, using cloth bags is the best example for reusing.

6. Recycling

· The process by which waste materials are used to make new products is called recycling. Using old clothes to make paper and melting some plastics to make floor mats, plastic boards and ose pipes are example of recycling.

· Though we use several methods, 3R - reducing, reusing and recycling play an important role in disposal of garbage.

Benefits of garbage disposal

· Pollution of air, water and land is reduced.

· Natural resources such as trees and metals are protected.

· Clean and hygienic surrounding is made.

· Unnecessary expenses are avoided.


· Vermicomposting is a type of composting where the organic wastes are degraded by using earthworms.

· The manure obtained by this process is called vermicompost.

Choose the correct answer

1. _____________decomposes degradable substances in the soil?

a) micro-organism b) earthworm c) bird d) both 'a' and 'b'

Answer: d) both 'a' and 'b'

2. An example for non-biodegradable product is____________?

a) paper b) cloth c) polythene bag d) fodder

Answer: c) polythene bag 

3. Waste that can be converted into manure is _________?

a) glass b) plastic c) metal d) household waste

Answer: d) household waste

4. Bio-medical wastes can be removed by ___________?

a) landfill b) composting c) incineration d)recycling

Answer: c) incineration

5. Organism used in vermicomposting is _____________?

a) leech b) roundworm c) earthworm d) tapeworm

Answer: c) earthworm 

Match the following (Matched)

1. Household waste - peel of vegetables and fruits 

2. Industrial waste - chemicals 

3. Agricultural waste - fertilizers, pesticides 

4. Medicinal waste - medicines, syringes 

5. Automobile waste - smoke 

Points to Remember

· Indraprastha Park in New Delhi is built on a landfill site.

· In 1862 Plastic was introduced for the first time in International Trade fair at London.

· In a vehicle only 30 % of fuel is used for driving, 70% of fuel is released as Carbon monoxide which is a poisonous gas.

· In a day an earthworm consumes food equal to its weight.

· June 5th is the World Environmental Day.

· When plastic is burnt, the harmful gas called dioxin is released.
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