4th Class Science Our Environment

Our Environment

Category : 4th Class


                                                           Our Environment


Our Environment is composed of physical and biological things surrounding us. It has physical or abiotic factor and biological or biotic factor. Physical components includes soil, air, water, minerals and other nonliving things around us. Biological components includes plants, animals and micro- organisms.



Pollution is the undesirable change in the physical, chemical and biological constituents of our surroundings. Pollution is of various types:


Air Pollution

Air pollution occurs when the air contains dust particles, gases, fumes in that amount which is harmful for us. The substances causing air pollution are called air pollutants.

Industries and vehicles discharge harmful gases into the air making it dirty and unfit for breathing.

Sun has ultraviolet rays which are absorbed by ozone layer present in the atmosphere. These rays can cause skin cancer. Due to air pollution ozone layer is getting depleted.


Effects of Air Pollution

Air pollution has various effects which are explained below.


Breathing Problem

When we inhale polluted air, it causes breathing problems. Bronchitis and asthma are diseases caused by air pollution.


Global Warming

Human inhales oxygen and gives out carbon dioxide, when amount of carbon dioxide increases in air, it causes global warming. Global warming is the heating up of atmosphere due to excessive amount of carbon dioxide in the air.


Acid Rain

Sometimes harmful gases discharged by factories and vehicles mixes with water vapours in the clouds. When it rains, these harmful gases get mixed with water vapours and comes down as acid rain. It affects forests, soil and human health. It makes soil more acidic. It also damages buildings, monuments etc.


Water Pollution

When toxic substances enter lakes, rivers, oceans and other water bodies, it causes water pollution. There are many sources of water pollution. Sewage from cities is thrown into water resources without treatment. Polluted water causes diseases like jaundice, typhoid, diarrhea etc.


Factories discharges harmful chemicals directly into water which causes damage to aquatic plants and animals.


Soil Pollution

Land gets polluted when we dump garbage on it.


Wastes are of two types:

Biodegradable: Things like fruits, vegetable peels/ paper etc. get decayed by microorganisms and mixes with soil.


Non-biodegradable: Things like plastic, polythene which do not get decayed by microorganisms and remains as it is in the soil and pollute the soil.




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