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Notes of Natural Resources Class 9: Learn & Revise

Important topics covered in natural resources notes:

  • Natural resources
  • Air: The breath of life
  • The role of atmosphere in climate control
  • Wind
  • Rain
  • Air Pollution
  • Water
  • Water pollution
  • Mineral riches in soil
  • Biogeochemical cycles
  • The water cycle
  • The nitrogen cycle
  • The Carbon cycle
  • The Oxygen cycle
  • Green House Effect
  • Ozone Layer

Natural Resources:

  • The materials or substances occurring in nature which can be exploited for economic gain is said to be natural resources.
  • Resources like soil, water, air, solar energy etc. are the life support systems on this earth.
  • There is need to conserve natural resources and use them in sustainable manner.
  • On this earth the resources are used in a cyclic fashion which creates a balance between the various components of the biosphere.
  • The outermost crust of the earth is called lithosphere.
  • The earth is covered by 75% of the portion of the earth and comprise of hydrosphere.
  • The air which covers the whole earth as a blanket is called atmosphere.

What is Biosphere?


  • Atmosphere, hydrosphere and lithosphere interact with each other to make life possible on this earth is said to be biosphere.
  • Biosphere is composed of two components. They are:

Biotic components:

  • Living component on this earth is called biotic components.
  • Plants and animals are examples of biotic components.

Abiotic components:

  • Non-living component present on this earth is called abiotic components.
  • Air, water and soil are the examples of abiotic components.


  • The atmosphere or air comprises of several gases.
  • Life is available on the earth because of these gases especially oxygen.
  • The oxygen present in the atmosphere is essential for all living organism for respiration.
  • Other planets such as Mars and Venus contain majorly carbon dioxide (95% to 97%) that is why life cannot exist there.
  • So, oxygen is regarded as called breath of life.

Role of atmosphere:

role of atmosphere

  • During the daytime, presence of gases around the earth prevents an increase in the temperature of the earth.
  • The harmful radiations of the sun is prevented from reaching the Earth’s surface by the atmosphere.
  • The atmosphere also prevents the heat emissions from the earth surface during the night time.
  • There is no atmosphere at moon so it faces extreme temperature conditions.


  • Moving air is called wind.
  • In the day time the direction of air is from sea to land. As the earth becomes hot in the day and starts rising.
  • During the night time the direction of wind is opposite to that of day as both land and sea cools.
  • This movement of air from one region to another is called wind. Also these condition causes Storms, Breezes and Rains.

Wind in coastal regions:

coastal wind

  • The land in the coastal areas gets heated faster than the sea during the daytime.
  • Since, the air present above the land rises above and creates a region of low pressure.
  • Now, the air present above the sea moves to low pressure region.
  • This is the fact how winds is created in the coastal area during the day.

Factors responsible for formation of winds:

  • The non-uniform heating of the Earth’s atmosphere
  • Earth’s rotation.
  • Mountains present on the earth is also responsible for formation of winds.

Air Pollution:

air pollution effects and causes

  • The increase in toxic substance in the air is causes air pollution.
  • Toxic substance are carbon dioxide, carbon monoxide, oxides of sulphur, nitrogen, fluorides etc.
  • Air pollution has great impact on respiratory and renal problems, eye irritation as well as also can cause cancer.
  • Reduced growth, degeneration of chlorophyll, mottling of leaves is caused to plants by air pollution.

Causes of air pollution:

air pollution

  • Burning of Fossil Fuels –Coal and petroleum on burning releases sulphur and nitrogen oxides which are harmful agents. Unburnt carbon particles are also released in the air called Hydrocarbons.
  • Exhaust from Industries – By the chimneys of many industries releases harmful gases which affects the environment by degrading the quality of air.
  • Mining – Harmful chemicals released in the air during mining causes air pollution.
  • Indoor Activities – Paints used in houses or some cleansing agents release harmful chemicals which pollutes the air.
  • Suspended Particulate Matter – Air quality is also degraded by the particles such as dust which often remain suspended in the air. Air pollution in the cities is mainly caused by it.


rain as natural resource

  • The process of evaporation, condensation of water through water cycle in which distribution of water takes place causes rain.
  • Rain is also an important factor for survival as it supports irrigation purpose.
  • Rain-water harvesting can be the one method to conserve water for irrigation as well as for future use.

Acid rain:

  • As we see that tons of fossil fuels are burnt everyday which releases smoke containing many harmful chemicals such as Sulphur dioxide (SO2), Nitrogen dioxide (NO2) etc.
  • When these harmful gases dissolve in rain water forms Sulphuric acid and nitric acid.
  • When it rains the water containing acid falls on the earth. Thus called acid rain.

Green House Effect:

greenhouse effect

  • The presence of carbon dioxide on the earth keeps the atmosphere warm.
  • The increase in temperature of the atmosphere is called green-house effect.
  • This is called green-house effect because the glass present in the green house keeps it warm.

Effect of increase in COin atmosphere:

  • Causes green-house effect.
  • Also cause global warming.
  • Average temperature of earth increase with increase in concentration of CO2.

Remember: The change in the surrounding environment affect us and our activities affect our surrounding environment.

Ozone layer depletion:

ozone layer depletion

  • Ozone (O3) is the allotrope of oxygen and is made up of 3 atoms of oxygen.
  • The ozone layer is present from 16 to 60 km above the sea level in the atmosphere.
  • UV rays coming from the sun is filtered by ozone layer, thus saves earth from harmful radiation.
  • The harmful impact of UV rays include skin cancer, cataract in eyes, immune system weakening.

Cause of Ozone layer depletion:

cause of ozone layer depletion

  • Excessive use of CFCs (Chloro-fluoro Carbon) in air condition, refrigerators, jet planes, Spray cans, fire extinguishers etc.
  • By nuclear fusion.



  • One of the major type of air pollution is smog.
  • Smoke + fog constitutes smog.
  • Smog is mainly found in cities where there is lot of air pollution.


  • The biodiversity of that area is determined by the presence of water to a great extent.
  • Cellular processes always take place in the water-like-medium.
  • Our blood contains water in a large proportion which allows it to carry substances throughout the body.
  • Water controls our body temperature in human beings and animals.
  • Water keeps tissues, organs and cells moist to prevent it from dying.
  • It helps in the removal of waste products out of the cells by osmosis/diffusion.
  • Digestion process in our body is carried out by water.
  • Transportation of food in different parts of plants such as the stem and leaves is carried out with the help of water.
  • It also has a main role in the process of photosynthesis.

Water Pollution:

water pollution

  • When harmful substances such as chemicals and non-biodegradable waste materials are present in water that affect its quality.
  • The aquatic life majorly affected by water pollution.

Causes of water pollution:

  • Waste from Industries – Water pollution is mainly caused by industries. They often release chemicals directly into water bodies. These chemicals contaminate them.
  • Sewage – Every day from every household tons of waste material is released to rivers which makes water pollute.
  • Mining Activities –The aquatic life is majorly affected by the metal wastes obtained from mining activities.
  • Usage of Fertilizers and Pesticides – The chemicals present in fertilizers and pesticides are non-biodegradable. They are extremely harmful to aquatic animals, plants as well as animal consumption.
  • Washing of clothes near rivers or water bodies.
  • Spraying chemicals in the water field.


  • Soil is the part of earth which provides support to plants and animals.
  • Soil consists of disintegrated rocks and decaying organic material and different nutrients that can help in sustaining life on earth.
  • These rocks breakdown through some chemical, biological and physical processes which leads to the formation of a nutrient-rich soil.

Soil Profile:

soil profile explanation with diagram

  • As the soil is formed it is found to be arranged in several layers.
  • The layers of the soil are also known to be
  • Each layer have different types of soil particles as well as colour.
  • The vertical section of soil that represents the sequence of layers to the soil is said to be soil profile.
  • The usage of that soil can be understood by these layers of the soil.
  • There are mainly 4 layers of soil and is called Mature Soil.
  • The types of soils which consist of only two layers only are said to be Immature Soils.

Horizons of soil (Layers of soil):

All the four layers of soil are given below:

The Humus Layer or “the topsoil” or “Horizon-A”

  • Organic matter and decomposed substances are present in this layer.
  • Most living organisms (earthworms, fungi, bacteria etc.) are found in the topsoil.
  • The topsoil is porous and can hold air and water in good amounts so organisms find it easy to survive.
  • It is dark in color.


  • This layer is filled with organic matter (i.e. decomposed leaves and humus in large amount)
  • It is also known as the organic layer of the soil.

Subsoil or Horizon B

  • Subsoil lies just below the topsoil and is hard as well as compact than the topsoil.
  • The subsoil has a light color because it does not contain much humus.
  • The subsoil contains minerals in good quantity and metal salts like iron oxide but does not contain much organic matter.
  • Farmers often mix the topsoil and subsoil so that the crops can get appropriate nutrition and grow easily.

Horizon C or Regolith:

  • This layer lies beneath the subsoil layer.
  • It is very hard and consists of stones and partly weather pieces of rocks. There is no organic matter in this layer. The roots of plants and trees cannot penetrate up to this layer.

Horizon-R or Bedrock:

  • Unweathered rocks are present in this layer.
  • This is the last layer of soil.

Formation of Soil: Several factors

  • There are several factors associated with the formation of soil. They are:


  • The breaking down of the rocks into smaller pieces and forming cracks in between them is caused by sun.
  • The rocks expand during the daytime as sun’s radiations heat it up.
  • But contract during the night, as rocks cools down.
  • It is obvious that all the parts of the rocks may not heat up or cool down at the same time.
  • By all these measures there forms cracks in them and ultimately breaks them down.


  • Water from different sources gets into the cracks of the rocks.
  • There it freezes down.
  • Cracks become whiten due to this.
  • Often the flowing water carries rocks with it.
  • The rocks get broken down into smaller pieces when carried by flowing water.
  • The rocks get rub against each other and also due to the pressure of the flowing water.
  • The crushed form thus help in formation of soil.


  • When strong wind blows it carries away rocks with it and all gets rubbed with each other.
  • Strong winds can break rocks.
  • Winds is also a soil transferring agent as it carries away the soil or sand from one place to another.

Living organisms:

  • Lichens and moss grow on the rocks.
  • Lichens secrete a certain substance that can powder down a rock.
  • This powdered rock leads to the formation of soil.
  • Small plants such as moss often grow on rocks and break them down.
  • It may also happen that the roots of different plants and trees get into the rock’s surface and break it down or widen the cracks.

Composition of soil:

There are several things which contributes the composition.

  • Rocks small pieces
  • Humus which is bits of decayed living organisms.
  • Microscopic organisms
  • Several minerals and nutrients

Soil erosion:

soil erosion

  • The process in which the upper layer of the soil gets washed away thus leading to degradation in the soil’s quality is known to be soil erosion.
  • Rain, wind or human activities are the main cause which leads to soil erosion.

Causes of soil erosion:

  • Over-grazing of field
  • Removal of top soil by the action of wind (storms) and water (floods).
  • Deforestation which cause lack of trees on the upper surface which cause soil to be eroded by land and water.
  • Leaving land uncultivated for long time.

Earlier we have read about soil erosion , now in natural resources notes we have briefed it.

Major effects of soil erosion:

  • As topmost fertile soil gets eroded which results in loss of fertility.
  • In hilly areas it causes landslides.
  • The washed off soil creates logging of water drains and water reservoirs.

How can we prevent Soil Erosion?

afforestaion to prevent sol erosion

We can prevent soil erosion by:

  • Intensive cropping and mannerly irrigation.
  • Terrace farming or using ecofriendly technique.
  • Afforestation and planting more trees in open areas.
  • Making strong embankments along the river banks.

Biogeochemical cycles:

There are four main biogeochemical cycles which takes place on our planet. They are:

  • The Water Cycle
  • The Carbon Cycle
  • The Nitrogen Cycle
  • The Oxygen Cycle

Water Cycle:

water cycle explanation

The continuous movement of water from the sky to the ground and then back again is said to be water cycle.

Different stages are involved in water cycle. They are:

  • Evaporation – Water from the Earth evaporates into water vapors due to solar heat and travels up to the atmosphere.
  • Transpiration: Plants extract water from their roots and excess of water in it is released in the atmosphere through root, stem, leaves etc.
  • Condensation – The water then cools and forms clouds up in the atmosphere.
  • Rainfall, Snowfall or Precipitation – After condensation the water falls on the earth in the form of rain, snowfall, hail or sleet.
  • The water that falls on the earth is utilized and through several pathways it reaches back to its initial position i.e. sea, ocean etc.
  • The process of circulation of water continues in the form of the water cycle.

The Carbon Cycle:

carbon cycle in atmosphere

  • The process by which carbon moves from the atmosphere into the Earth and it’s and then back to it again is said to be carbon cycle.

The importance of carbon on the planet Earth:

  • Carbon is present in the form of carbon dioxide which is needed by organisms on this earth to survive.
  • Minerals contain carbonates and hydrocarbons.
  • All life forms in proteins, fats, vitamins and carbohydrates contain carbon dioxide.
  • In animals the internal skeleton (endoskeleton) and external skeleton (exoskeleton) is made up of carbon salts.
  • During photosynthesis plants convert carbon into glucose molecules.

Carbon cycle involves the following processes:

  • Photosynthesis: By absorbing the atmospheric carbon in the form of carbon dioxide gas plants produce their food and release oxygen gas.
  • Respiration: Plants and animals respire resulting in breakdown of glucose stored in the plants and animals to release CO2, water and energy.
  • Decomposition: Dead plants and animals get decomposed and release carbon into the environment.
  • Combustion: A large amount of combustion of fossil fuels daily releases carbon dioxide gas into the environment as by product.
  • Transfer of carbon from the atmosphere to the oceans: Several water bodies mainly oceans soak up about a quarter of the carbon dioxide to form carbonates inside it.
  • The concentration of carbon dioxide in air remains same every time due to carbon cycle.

Natural resources notes contain all the important topics to learn for CBSE board exam.

Nitrogen Cycle:

nitrogen cycle

The sequence in which nitrogen passes from the atmosphere to the soil and organisms, and then is eventually released back into the atmosphere thus completes nitrogen cycle.

The following process are involved in the process of Nitrogen Cycle:

  • Nitrogen fixation: when atmospheric nitrogen is converted into the form which can be easily absorbed the organisms on earth is said to be nitrogen fixation.

By lightning: The high temperature and pressure created during lightning convert nitrogen and water into nitrates and nitrites which get dissolved in water and aquatic plants and animals uses it.

By bacteria: Free living bacteria or the bacteria like Rhizobium present in the root nodules of legumes converts molecular nitrogen into nitrates and nitrites.

  • Nitrification: The process in which ammonia is converted into nitrites and nitrates is called nitrification.
  • Ammonification: The process in which soil bacteria decompose dead organic matter and release ammonia into soil is called ammonification.
  • De-nitrification: In this process nitrates are converted into atmospheric nitrogen back to complete the cycle.

Oxygen cycle:

oxygen cycle

The cyclic process by which oxygen is circulated continuously through the living and non-living components and the quantity is maintained in the atmosphere is said to be oxygen cycle.

Importance of Oxygen on this earth:

  • The second most abundant gas present in the atmosphere (21%) is oxygen.
  • Mainly oxides in metals and minerals are present on earth crust.
  • In carbon dioxide it is in combined form.
  • Almost all biological compounds like proteins, carbohydrates and fats contains oxygen.

Process involved in the oxygen cycle:

  • Respiration: Every living organisms on this earth take simple sugars (glucose) in and oxygen and release carbon dioxide, water and energy.
  • Combustion: Oxygen is the main component which required for combustion.
  • Photosynthesis: In the process of photosynthesis carbon dioxide is used as ingredient to produce and release oxygen.

Further about this chapter we will read in higher section natural resources notes. To score better in examination one must learn each topic mannerly.


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