short notes of chapter natural resources class 9th
Answers
Key notes for Chapter - Natural Resources, are:
Rain
Rain is formed by evaporation and condensation of water through water cycle in.
Acid Rain
Acid rain is caused by the release of the gases like SO2 (sulphur dioxide) and NO2 (nitrogen dioxide) released from the emission of vehicles and combustion of fuels. These gases dissolve in rain water to form nitric acid and sulphuric acid.
Water
Water is renewable resource.
It is essential for all physiological activities of plants and animals.
Water is mainly present in two forms:
(i) Surface water
(ii) Ground water.
Water Pollution
An undesirable change in the physical, biological or chemical properties of water (due to addition for foreign organic, inorganic substances) that adversely affects the aquatic life, and makes water less fit or unfit for use, is called water pollution.
The main causes of water pollution are as follows:
(i) Addition of harmful substances like fertilisers and pesticides to water
(ii) Removal of desirable substances like oxygen from water
(iii) Change in water temperature
Soil
It is the uppermost layer of Earth’s crust, which supports terrestrial plants, animals and microorganisms.
It is formed from the weathering of rocks by physical, chemical and biological activities by the action of wind, water and sun.
It is made up mainly of mineral particles, organic materials, air, water and living organisms
Humus : The decayed living organisms present in soil is called humus.
Humus makes the soil porous and allows water and air to penetrate deep underground making the soil more fertile.
Soil pollution :
Removal of useful components from the soil and addition of other substances, which adversely affect the fertility of the soil and kill micro-organisms living in it is called soil pollution.
Fertilizers and pesticides destroy the soil structure.
Mosses or Bryophytes are indicator of soil pollution.
Soil Erosion
Removal of topmost layer of soil by wind, water or other activities is called soil erosion.
Causes of soil erosion
Main factors responsible for the soil erosion are:
Over grazing of land.
Removal of top soil by wind (storms) and water (floods).
Deforestation
Leaving land uncultivated for long time.
Effects of Soil Erosion:
Loss of fertility due to loss of topmost fertile soil which results in desertification.
Landslides in hilly areas.
Clogging of water drains and water reservoirs by the washed off soil.
Prevention of Soil Erosion:
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