Maharashtra Board Class 11 Environmental Science Chapter 4 Natural Resources PDF Download

4. Natural Resources

Man depends upon a large number of goods and services provided by nature. The water, air, soil, minerals, coal are abiotic resources. Forest resources, crops, wildlife and marine flora and fauna are all examples of biotic resources. Any material which is required or used to sustain life or livelihood is termed as a resource. Natural resources are defined as a form of energy and/or matter which is essential for the functioning of organisms, populations and ecosystems.

Natural resources can be classified into two categories: (i) Renewable resources (ii) Non-renewable resources.

i. Renewable resources: These are the resources that are replenished by the environment over relatively short period of time. These floral and faunal resources are able to increase through reproduction and utilization of simple substances. Example: Plants regenerate through biogeochemical cycles and photosynthesis.

ii. Non-renewable resources: These are the resources that are not easily replenished by the environment. These are available in limited amounts, which cannot be increased. Example: Coal, petroleum, minerals, natural gas.

Solar energy, geothermal energy are considered perpetual resources.

Non-renewable resources can be further divided into two categories:

i. Recyclable: These are non-renewable resources, which can be collected after they are used and can be reused and recycled. These are mainly the mineral resources, which occur in the earth's crust and deposits. Eg. Iron metal items which can be recycled after use.

ii. Non-recyclable: These are non renewable resources, which cannot be recycled in any way. Example: Fossil fuels and uranium, which provide 90% of our energy requirement.

4.1 Water As A Natural Resource

Without water there would be no life on the earth. Fresh water is the main resource on earth without it there would be no plants or animals. Human beings require water not only to drink but also to grow crop, operate industries and to provide hydro electric energy. Water is an indispensable natural resource on this earth on which all life depends. About 97% of the earth's surface is covered by water and most of the animals and plants have 60-65% water in their bodies.

Distribution Of Water Resources On Earth's Water

Teacher's Note

Water is very important for life. In India, many villages do not have clean drinking water. We must save water every day like our grandparents did.

Exam Trick

Remember: 97% water is salty ocean water. Only 3% is fresh water. And only 0.003% is easy to drink! Think of it like money - most is locked away, very little is free to use.

Points to Remember

Water covers 97% of Earth but most is salty.
Only 2.5% of Earth's water is fresh water.
Only 1% of fresh water is easy to get for drinking.
97% of water is in oceans and is salty.
Plants and animals have 60-65% water in their bodies.

Freshwater makes up a very small fraction of all water on the planet. Nearly 71% of the earth is covered by water only 2.5% of it is fresh water. The rest is saline water in the oceans. Only 1% of freshwater is available as much of it is trapped in glaciers and the Arctic and Antarctic circles.

Classification Of Water Resources

Surface water resources: The surface water generally originates from the following:

Precipitation in the form of snowfall and rainfall.

Underground water resources It is the natural storage of water due to percolation of rain water through the soil. The quality of ground water is usually clean, clear and fresh as it gets filtered naturally. This water is mostly used for the agricultural purposes and domestic use.

Due to these unique properties water has of multiple use for all living organisms. Water is absolutely essential for life. Most of the life processes takes place in the tissue fluids in flora and fauna. Uptake of nutrients, their distribution in the body, regulation of temperature and removal of wastes are all maintained through water.

About 9.86% of the total fresh water resources is in the form of groundwater. Overuse of groundwater for drinking, irrigation and domestic purposes has resulted in rapid depletion of groundwater levels in various regions leading to lowering of water table and drying of wells. Pollution of many groundwater aquifers has made the well water unfit for consumption. Rivers and streams are used for discharging urban, industrial and agriculture waste. Most of the civilizations have flourished on the banks of rivers, but, in turn they became sources of pollution for the rivers.

Teacher's Note

Most fresh water is trapped in ice. We get very little water for drinking. India's rivers like Ganga are getting polluted and we must stop this.

Exam Trick

Remember: Ground water = water under soil. It is clean at first but people are using too much. Soon wells will become dry like in Rajasthan!

Points to Remember

Surface water comes from rain and snow falling on land.
Ground water is stored water under the soil.
Ground water is usually clean and fresh.
About 9.86% of fresh water is ground water.
Over using ground water makes wells dry.

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