- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
→ Life on earth depends on resources like soil, water, air and energy from sun.
→ Uneven heating of air over land and water-bodies causes winds.
→ Evaporation of water from water-bodies and subsequent condensation give us rain.
→ Pollution of air, water and soil affect the quality of life.
→ We need to conserve our natural resources and use them in a sustainable manner.
→Various nutrients are used again and again in a cycle fashion. This leads to a certain balance
between the various components of the biosphere.
→ The resources available on the earth and the energy from the sun are necessary to meet the
basic requirements of all life forms on the earth.
→ The stocks of nature which are useful to mankind are known as natural resources.
Examples: air, water, soil, minerals etc.
Resources on the earth
→ The outermost crust of the earth is called the lithosphere.
→ Water covers 75% of the earth’s surface. It is also found underground. These comprise the
→ The air that covers the whole of the earth like blanket is called the atmosphere.
→ All living things on earth together with atmosphere, the hydrosphere and the lithosphere intera
and make life possible is known as biosphere.
• It may be:
(i) Biotic components: Plants and animals.
(ii) Abiotic components: Air, water and soil.
- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
→ The flow of substances from non-living to living and back to non-living is called the cycling of
→ The cycling of chemical elements like carbon, oxygen, nitrogen, phosphorus, sulphur and water
the biosphere is called biogeochemical cycle.
→ It operates through soil, water, air and biotic factors.
→ The whole process in which water evaporates and falls on the land as rain and later flows back
into the sea via rivers is known as water cycle.
→ When sun shines, water evaporates continuously from the water bodies and forms water vapour
This water vapour rises up and goes into the atmosphere.
→ The plants absorb water from the soil and use it during the process of photosynthesis.
→ They also loose water by the process of transpiration.
→ The water vapour produced by transpiration also goes into the atmosphere.
→ The process of respiration and evaporation from the surface of animal body produces water
vapour which goes into the atmosphere.
→ The evaporation and condensation of water vapour leads to rain. During winter, the water falls
down in the form of dew or snow.
→ All of the water that falls on the land does not immediately flow back into the sea. Some of it
seeps into the soil and becomes part of the underground reservoir of fresh water.
→ The underground water is again taken by plants and water cycle continues.
→ The percentage of oxygen in air is 21%.
→ The cyclic process by which oxygen element is circulated continuously through the living and
non-living components of the biosphere constitutes oxygen cycle.
→ Human beings and animals take oxygen from the atmosphere during the process of respiration
→ The decomposition of dead organisms also takes in oxygen from the atmosphere.
→ Respiration and decay of dead organisms release CO2 and water.
→ The carbon dioxide and water are used by the green plants during the process of photosynthesis
→ They give out oxygen during this process. This oxygen is again used by human beings and
→ Thus, the oxyen cycle keeps repeating in nature.
→ 0.03-0.04% carbon is present in the atmosphere in the form of CO2.
→ Carbon cycle maintains the balance of the element carbon in the atmosphere. Carbon is found
various forms on the earth.
→ Carbon is present in the atmosphere as carbon dioxide.
→ Carbon can also occur as carbonates and bicarbonate salts in minerals.
→ Carbon is the essential part of nutrients like carbohydrates, fats, proteins, nucleic acids and
→ Carbon cycle keeps the level of CO2 constant in the atmosphere.
• The Carbon Cycle starts in plants as:
Step I: Plants use CO2 in the atmosphere, convert it into glucose in the presence of sunlight by the
process of photosynthesis. Plants and animals break these carbohydrates for energy and release
CO2 through respiration.
Step II: When the plants and animals die, fungi and bacteria decompose the dead remains. This
releases the carbon in the remains as carbon dioxide.
Step III: Some of the dead plants and animals which get buried under the earth under certain
temperature and pressure get transformed into fossil fuels like coal and petroleum.
→ On burning these fuels, CO2 is released into the atmosphere.
→ The sequence in which nitrogen passes from the atmosphere to the soil and organisms, and then it
is eventually released back into the atmosphere, is called nitrogen cycle.
→ Nitrogen makes up 78% of the earth’s atmosphere.
→ Nitrogen is an essential constituent of proteins, nucleic acids like DNA and RNA, vitamins and chlorophyll.
→ Plants and animals cannot utilize atmospheric nitrogen readily.
→ It has to be fixed by some organisms called nitrogen fixers.
→ Nitrogen-fixing bacteria like Rhizobium live in symbiotic association in the root nodules of certain
→ These bacteria convert atmospheric nitrogen into ammonia which is utilized readily by plants.
→ Nitrogen-fixing bacteria along with free living bacteria in the soil achieve 90% of nitrogen fixation
→ Lightning plays an important role in nitrogen fixation. When lightning occurs, the high
temperature and pressure convert nitrogen and water into nitrates and nitrites.
→ Nitrates and nitrites dissolve in water and are readily used by aquatic plants and animals.
• Ammonification: It is the process by which soil bacteria decompose dead organic matter and
release ammonia into soil.
• Nitrification: It is the process by which ammonia is converted into nitrites and nitrates.
• Denitrification: It is the process by which nitrates are converted into atmospheric nitrogen.
- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
→ Air is a mixture of different gases.
→ Air contains oxygen which is essential to living organisms for respiration. So it is called breath of
Role of Atmosphere
→ Air is a bad conductor of heat. It keeps the average temperature of the earth constant during th
day and even during the course of the whole year.
→ Prevents the sudden increase in temperature during day time and during the night, it slows dow
the escape of heat into outer space.
Example: At moon, there is no atmosphere and so the temperature varies from 190ºC to 110ºC.
- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
The Movement of Air: Winds
→ During the day, the direction of wind is from sea to land. This is because the air above the land
gets heated faster and starts rising.
→ During the night, the direction of wind is from land to sea. This is because at night, both land an
sea start to cool.
→ The movement of air from one region to the other creates winds.
→ Rain is formed by evaporation and condensation of water through water cycle in which
distribution of water takes place.
→ Rain is very important because it carries out all the agriculture processes in the plants.
→ So we should conserve rain by contracting dams, pools etc.
→ When fossil fuels are burnt, gases like sulphur dioxide and nitrogen dioxide (NO2) are released.
→ These gases are dissolving in water form nitric acid and sulphuric acid.
- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
→ Air is a mixture of different gases.
→ Air contains oxygen which is essential to living organisms for respiration. So it is called breath o
→ An increase in the content of harmful substance (pollutants) in the air like carbon dioxide, carb
monoxide, oxides of sulphur, nitrogen, fluoride, lead, nickel, arsenic and dust particles etc. causes a
Air pollution can cause:
• In humans: Respiratory and renal problems, high blood pressure, eye irritation, cancer.
• In plants: Reduced growth, degeneration of chlorophyll, mottling (patches/spots of colour) of
Water: A wonder Liquid
→ The most unusual natural compound found on earth and which fulfills almost various demands
different living things.
→ About three-fourth of the earth surface is 75% are covered with water.
→ It is present underground, a very large area on the surface (sea, ocean etc.) and also in the form
of water vapour in the atmosphere.
Necessity of Water for all Organisms
→ It maintains a uniform temperature of the body.
→ All cellular processes take place in a water medium.
→ All the reactions that take place within our body and within our cells occur between substances
that are dissolved in water.
→ Water forms the habitat of many plants and animals.
→ When water becomes unfit for drinking and other uses, then water is said to be polluted.
Causes of Water Pollution
→ Dumping of wastes from the industries into water bodies.
→ Washing of clothes near water bodies.
→ Spraying chemical in water field.
→ Dumping household wastes into the water bodies.
→ Soil is the portion of the earth surface consisting of disintegrated rock and decaying organic
material. It provides the support for many plants and animals.
Creation of Soil: Various Factors
→ The sun heats up rocks during the day so that they expand. At night these rocks cool down and
→ Since all parts of the rocks do not expand and contract at the same rate, this results in the
formation of cracks and ultimately the huge rocks breaks up into smaller pieces.
→ Fast flowing water carries big and small particles of rock downstream. These rocks rub against
other rocks and the resultant abrasion causes the rocks to wear down into smaller particles.
→ Wind carries sand from one place to another.
→ Lichen (A slow growing plant)
→ Lichen, moss also grow on surface of rocks. While growing, they release certain substances tha
cause the rock surface to powder down and form a thin layer of soil.
→ Carrying away of upper fertile layer of soil by rain, wind, human activities and wrong agricultura
practice is called soil erosion.
Causes of soil erosion
→ Over grazing of land.
→ Removal of top soil by wind and water.
→ Due to lack of trees the upper layer of soil is eroded by air and water.
→ Leaving land uncultivated for long time.
- Books Name
- Science Made Easy Science Book
- Science Made Easy
- CBSE Class 9
Green House Effect
→ Carbon dioxide keeps the earth warm much like glass which keeps the green house warm.
• Effect of Increase in carbon dioxide (CO2):
(i) intensifies green house effect.
(ii) leads to global warming.
(iii) increase in average temperature of earth.
(iv) may lead to melting of polar caps.
(v) sub-merging number of coastal cities.
→ Changes in environment affects us and our acitivities change the environment around us.
Environmental Problems Caused by Humans
Depletion of Ozone Layer
→ Ozone layer is a protective blanket around the earth which absorbs most of the harmful UV
(ultraviolet) radiations of the sunlight, thus protecting living beings from many health hazards such
as skin cancer, cataract, destruction of plants etc.
→ Ozone (O3) layer is present at higher levels of atmosphere (i.e. stratosphere). It is a deadly poisonous at ground level.
→ Ozone layer is present in the stratosphere which is a part of our atmosphere from 16 km to 60 km
above sea level.
→ Ozone is an allotrope of oxygen. Its molecule is made up of three oxygen atoms. Molecular
formula is O3.
→ Ozone layer absorbs the ultra-violet rays coming from the sun and protects living being from
their harmful effects like skin cancer, cataract in eyes, weaken immune system.
→ The decline of ozone layer thickness in Antartica was first observed in 1985 and was termed as
Reason of Ozone Depletion
→ Excessive use of CFCs (Chloro Fluoro Carbon) in refrigeratos, jet planes, spray cans, fire
→ Nuclear explosion
→ Smog is a type of air pollution.
→ The word ‘smog’ comes from the blend of two words: Smoke and fog.
→ Smog can form in any climate where there is a lot of air pollution especially in cities.
Formation of ozone molecule
(i) The high energy UV radiations break down the O2 molecules into free oxygen (O) atoms.
O2 +uv → O + O (atoms)
(ii) These oxygen atoms then combine with oxygen (O2) molecule to form the ozone molecule.
O2 + O → O3 (ozone)
Depletion of ozone layer
→ The decrease in the thickness of ozone layer over Antarctica was first observed in 1985 and was
termed as ozone hole.
→ This decrease was linked to excessive use of synthetic chemicals like chlorofluorocarbons (CFC
which are used in refrigerators, ACs, fire-extinguishers, aerosols sprays etc.
→ United Nations Environment Programme (UNEP) succeeded in forging an agreement to stop CFC
production at 1986 levels (KYOTO PROTOCOL) by all countries.
Life on Earth is possible because of the presence of these three major sources. A zone where the lithosphere, the atmosphere and the hydrosphere intersect and the life sustains is called the Biosphere.
The biosphere can be divided into two parts:
The biosphere can be divided into two parts:
• Abiotic Components – The non-living things such as air, water and land
• Biotic Components – The living things such as plants and animals
Resource – A Resource is a stock or supply of something useful. Resources can be manmade or Natural.
Natural Resources – A Resource which exists in nature is called a Natural Resource. It is not produced by any human being; rather it is available in nature itself. Human beings and other animals depend upon these resources for their existence.
Natural Resources present on Earth:
• Air – The atmosphere which contains different gases such as Oxygen, Nitrogen and carbon dioxide which are required for the survival of life on earth.
• Water – The hydrosphere which covers almost 75% of the Earth surface. It is a home to an abundance of animals and plants and is also required for the survival of life on earth.
• Land – The upper crust of the earth is called Lithosphere where different kinds of soils are found which are necessary for the growth of plants and are a home to several vitamins and minerals.
Improvement in Food Resources
All living organisms essentially require the food to stay alive.
Food provides energy to perform various life activities and is required for growth, development and body repair.
Sources of Food:
1. Food from agriculture: Cereals, pulses, vegetables, fruits, nuts, oilseeds, condiments and spices
2. Food from animal husbandry: Dairy products like milk, curd, butter; meat, egg, fish and other sea products.
Food Revolutions in India
With the increase in population, there needed a sufficient increase in food production, so as to meet the food related demands of growing population. This led to the rise of the following food revolutions in India:
1. Green Revolution: Introduced to increase the food grain production.
2. White Revolution: Introduced to increase production of milk.
3. Blue Revolution: Introduced to enhance fish production.
4. Yellow Revolution: Introduced to increase oil production.
Different crops require different climatic conditions like temperature, moisture and photoperiods to grow well and complete their life cycle.
Two main crops are:
1. Kharif crops:
• Grown in Summer season from the month of June to October, i.e., during rainy season.
• Crops grown in this season require more water.
• Examples of Kharif season crops are: Paddy, soyabean, pigeon pea, maize, black gram, green gram and rice are kharif season crops.
2. Rabi crops:
• Grown in Winter season from the month of November to April.
• Crops grown in this season require less water.
• Examples of Rabi season crops are: Wheat, gram, peas, mustard and linseed are rabi season crops.
What are nutrients?
Plants require some nutrients in large quantities called macronutrients while some in smaller quantities known as micronutrients.
Deficiency of these nutrients inhibits the growth of plants, affects their life cycle, processes and decreases their immunity against diseases. Soil’s fertility can be increased by providing nutrients in the form of manure and fertilizers.
Nutrient management refers to the efficient use of crops to improve productivity. It is necessary to balance the soil nutrient input with the crop requirement. If the nutrients are applied at the right time and in adequate quantities, optimum crop yield is obtained. If applied in huge amounts, it will harm the crop, and if applied in small quantities it limits the yield.
• Manure contains large quantities of organic matter and also supplies small quantities of nutrients to the soil.
• Manure is prepared by the decomposition of animal excreta and plant waste.
• Manure helps in enriching soil with nutrients and organic matter and increasing soil fertility.
• On the basis of the kind of biological waste used to make manure, it can be classified into three types:
(i) Compost (ii) Vermicompost (iii) Green manure.
(i) Compost: It can be farm waste material such as livestock excreta (cow dung etc.), vegetable waste, animal refuse, domestic waste, sewage waste, straw, eradicated weeds, etc. This material is decomposed in pits and this process of decomposition is also called composting. This compost is rich in organic matter and nutrients.
(ii) Vermicompost: The compost which is made by the decomposition of plant
and animal refuse with the help of redworm is called vermicompost.
(iii) Green manure: Prior to the sowing of the crop seeds, some plants like sun hemp or guar are grown and then mulched by ploughing them into the soil. These green plants thus turn into green manure which helps in enriching the soil in nitrogen and phosphorus.
• Fertilizers are commercially produced plant nutrients.
• Fertilizers supply nitrogen, phosphorus and potassium.
• They are used to ensure good vegetative growth (leaves, branches and flowers), giving rise to healthy plants.
• Fertilizers are an important factor in the higher yields of high-cost farming.
Pollution: Contamination of natural sources with unwanted substances.
The presence of harmful substances in the air leads to pollution of the air. It can severely affect the health of living organisms and the quality of the environment.
What causes Air Pollution?
• Burning of Fossil Fuels – When coal and petroleum are burnt, they release sulphur and nitrogen oxides which are harmful agents. They also release unburnt carbon particles in the air called Hydrocarbons.
• Exhaust from Industries – The industries release harmful gases and smoke in the air that contains carbon monoxide and organic compounds that decrease the quality of the air.
• Mining – During the mining process harmful chemicals are released in the air that leads to air pollution.
• Indoor Activities – Cleaning agents and paints used in houses release harmful chemicals which pollutes the air
• Suspended Particulate Matter – The particles such as dust often remain suspended in the air and degrade its quality. SPM is one of the major causes of air pollution in the cities.
What are the effects of Air Pollution?
• Acid Rains – Rains often contain acidic compounds that can affect animals, plants and crops.
• Harmful diseases and allergies – Inhalation of harmful substances can lead to diseases such as heart problems and cancer and allergic reactions in the skin and eyes.
• A decrease in the visibility – The suspended particles in the air affects the visibility and also lead to the formation of smog in the cold weather.
• Global Warming – The temperature of the earth rises due to the presence of greenhouse gases in it such as carbon dioxide and methane.
• Ozone Layer Depletion - The air pollution leads to depletion of the outer covering of the ozone layer around the earth’s atmosphere.
The different forms of water present on the earth are:
• Water Vapour – found in the atmosphere
• Saline Water – found in seas and oceans
• Freshwater – found in frozen ice caps, snow-covered mountains, underground, rivers, lakes and ponds
Why Water is necessary for Life?
• The presence of water in a region decides the biodiversity of that area to a great extent.
• The cellular processes take place in the water-like-medium.
• A major constituent of blood is water which allows it to carry substances throughout the body.
• Water helps in regulating the body temperature in animals and human beings.
• It prevents the tissues, organs and cells from drying out by keeping them moist.
• Water helps in digestion of food.
• Water helps in the removal of waste products out of the cells.
• Plants also require water to transport food through different parts such as the stem and leaves and also in the process of photosynthesis.
Water pollution occurs when harmful substances such as chemicals and waste materials like garbage are present in water that affect its quality and the presence of life in it.
Causes of Water Pollution
• Waste from Industries – The industries often release chemicals directly into water bodies such as rivers and seas which contaminates it.
• Sewage – The waste produced from households is often released into the water which gives rise to harmful bacteria in the water.
• Mining Activities – The metal wastes obtained from mining activities harm the organisms present in water
• Usage of Fertilizers and Pesticides – The chemicals present in fertilizers and pesticides are extremely harmful to aquatic animals, plants as well as animal consumption.
Effects of Water Pollution
• Addition of unwanted substances such as fertilizers pesticides and industrial wastes can make it poisonous and extremely harmful for consumption.
• It can also lead to an increase in bacteria that causes severe diseases like Cholera.
• Water pollution can lead to a decrease in the amount of Oxygen and nutrients in the water which affects the aquatic life.
• Water pollution can cause changes in the temperature of water. An increase in temperature is not suitable for all the aquatic animals especially their eggs.
Ozone Layer Depletion
It has been discovered that the Ozone Layer is getting depleted from the earth's atmosphere. A hole in Ozone Layer has been found over Antarctica.
• This is mainly because of the presence of the Chlorofluorocarbons (CFCs) in the atmosphere. These are released due to industrial processes, refrigeration, aerosols, foams and solvents.
• The chlorine and fluorine present in these on reaching the Ozone Layer react with it to form complex compounds and it thus results in depletion of Ozone.
- If the Ozone Layer would deplete the ultraviolet rays of the sun would under the Earth’s atmosphere which could lead to severe effects such as:
• An increase in the risk of having skin cancer
• Damaging the eyes
• The weakening of the immune systems
• Skin allergies
• Decay in the growth of plants and animals
• Breakdown of the natural carbon cycle
• Water harvesting is the collection of run off for productive purposes.
• Instead of run off being left to cause erosion, it is harvested and utilized.
• In the semi-arid drought-prone areas where it is already practiced, water harvesting is a directly productive form of soil and water conservation.
• Eutrophication is the process in which a water body becomes overly enriched with nutrients, leading to plentiful growth of simple plant life.
• The excessive growth (or bloom) of algae and plankton in a water body are indicators of this process.
• Eutrophication is considered to be a serious environmental concern since it often results in the deterioration of water quality and the depletion of dissolved oxygen in water bodies.
• Eutrophic waters can eventually become “dead zones” that are incapable of supporting life.
Biomagnification can be defined as the rise or increase in the contaminated substances caused by the intoxicating environment. The contaminants might be heavy metals such as mercury, arsenic, and pesticides such as polychlorinated biphenyls and DDT.
Causes of biomagnification.
The agricultural pesticides, insecticides, fertilizers and fungicides are very toxic and are released into the soil, rivers, lakes, and seas. These substances contain small amounts of heavy metals such as mercury, arsenic, copper, lead and cadmium. These cause health issues in aquatic organisms and humans.
- Organic Contaminants
Manures and biosolids are processed industrially and contain contaminants like pharmaceuticals and personal care products. These substances have an adverse impact on the health of humans, animals, and wildlife.
- Industrial Activities
The industries and factories release toxic substances that are released into the soil, lakes, oceans, and rivers. The gaseous emissions pollute the environment which enters into the food chain leading to biomagnification.
Effects of biomagnification on living organisms and the environment:
- Impact on Human Health
Biomagnification makes humans more prone to cancer, kidney problems, liver failure, birth defects, respiratory disorders, and heart diseases.
- Destruction of Coral reefs
Cyanide that is used in leaching gold and fishing is the main cause of the destruction of coral reefs. Coral reefs are the dwelling and feeding grounds for many sea creatures. Their destruction affects the lives of many aquatic animals.
- Disruption of Food Chain
The chemicals and toxins which are released into the water bodies disrupt the food chain. The small organisms absorb the toxins which are eaten up by larger animals. These toxins, thus, get accumulated in the higher level of organisms.
It is a mixture. It is the portion of earth surface consisting of various components like small particles of rock (of different sizes, bits of decayed living organisms which are called humus, various forms of microscopic life, air and water.
• The soil is found in several layers which are arranged as the soil is formed.
• The layers of the soil are also called as Horizons.
• These layers have different types of soil particles and colour and hands are differentiated on this basis.
• The soil profile is defined as the vertical section of soil that represents the sequence of layers to the soil.
• The layers of the soils help in understanding the usage of that soil.
• The soil mainly consists of four layers. Such a soil is called Mature Soil.
• Some types of soils consist of two layers only. They are called Immature Soils.
The Layers or Horizon of Soil
1. The Topsoil or Horizon A or the Humus Layer
• This layer of soil consists of organic matter and decomposed substances.
• It is dark in colour, porous and can hold air and water in good amounts.
• Due to such quality, many living organisms are found in the topsoil, for example, the earthworms, fungi and bacteria.
Some soils contain a layer of organic matter which consists of a large number of decomposed leaves and humus. It is called the organic layer of the soil.
2. Subsoil or Horizon B
• It lies below the topsoil. It is hard and compact than the topsoil.
• The subsoil has a light colour because it does not contain much humus.
• The subsoil does not contain much organic matter other but contains minerals in good quantity and metal salts like iron oxide.
• When farmers plough their field, they often mix the topsoil and subsoil so that the crops can grow easily.
3. 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.
4. Horizon R or Bedrock
This is the last layer of the soil which consists of un weathered rocks
Factors affecting the formation of Soil
- The Sun -
• It is responsible for breaking down the rocks into smaller pieces and forming cracks in between them.
• The sun's radiations heat up the rocks during the daytime. As a result, the rocks expand.
• But during the night, these rocks cool down and therefore contract.
• All the parts of the rocks may not cool down or heat up at the same time.
• All this leads to the formation of cracks in them and ultimately breaks them down.
2. Water –
• Water gets into the cracks of the rocks and freezes down there.
• This leads to whitening of the cracks.
• Flowing water often carries pieces of rocks away and on that path, they get broken down into smaller pieces as they rub against each other and also due to the pressure of the flowing water. This is one of the reasons why soil is formed far away from the parent Rock.
3. Winds –
• Winds can wear down the rocks and break them.
• Strong winds rub against the rocks and break them or wear them down just like water.
• Winds also carry away the soil or sand from one place to another.
4. Living organisms –
• Lichens that can grow on the rocks and secrete a certain substance that can powder down a rock which 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.
Soil is a mixture of various substances It contains the following:
• Small pieces of rocks
• Bits of decayed living organisms called the Humus
• Microscopic organisms
• Minerals and nutrients
Factors that decide the type of soil
• The amount of humus present in the soil – the more the humus the more porous and deep the soil is.
• The number of microscopic organisms in the soil – they help in keeping it fertile
• The parent rocks – they decide the minerals that are present in the soil
We know that soil contains different types of substances all of them are responsible for the sustenance of the biodiversity. When the useful components get removed from the soil, it loses its fertility and leads to a decrease in the microscopic life in it. This phenomenon is called soil pollution.
The Causes of Soil Pollution
• Long usage of fertilizers and pesticides leads to the killing of the microorganisms present in it. Without these organisms, the soil would not get recycled and replenished. Earthworms get killed because of the pesticides. They are the ones that lead to the formation of humus in the soil.
• Flowing water and winds can carry away the soil particles and often lead to exposure of rocks.
• Deforestation can also lead to soil pollution as the uprooting of trees exposes the soil to rains and winds.
• Industrial activities like mining and extraction of minerals can lead to a mixture of harmful chemicals in the soil and decay its quality.
Effects of Soil Pollution
• It severely affects the growth of plants.
• It can lead to infertility of soil and thus would restrict agriculture on such land.
• The fertilizers decay the quality of the soil.
• It can affect the health of human beings who consume food grown in soil which has large amounts of fertilizers and pesticides mixed in it.
• It can change the structure of soil thus decaying the growth of useful bacteria and other microorganisms in the soil.
Soil Erosion – It a process in which the upper layer of the soil gets washed away thus leading to degradation in the soil’s quality.
How can roots of plants prevents soil erosion?
• The roots of the plants bind the soil together and prevent the winds and flowing water to sweep away the soil particles.
• The plants also lead to the movement of water inside the soil and allow it to reach the deeper layer leading to an increase in the water retention of the soil and the underground water levels.
A biochemical cycle refers to the natural cycle of the earth through which a chemical substance or matter moves through the biotic and abiotic components of the earth. These components always interact with each other and form a stable system in the biosphere.
There are four main biogeochemical cycles
• The Water Cycle
• The Nitrogen Cycle
• The Carbon Cycle
• The Oxygen Cycle
The whole process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known as the water-cycle.
The water cycle in nature is also known as hydrological cycle. The various steps involved in the water cycle in the biosphere are:
Evaporation is when the sun heats up water in seas and oceans and turns it into water vapour or steam.
• The Sun’s heat provides energy to evaporate water from the Earth’s surface (oceans, lakes, etc.) and form water vapour which being lighter than air rises up and goes into the atmosphere.
2. Transpiration -The plants continuously absorb water from the soil through their roots.
• Some of this water is utilized by the plants for photosynthesis.
• The excess water in the body of plants is added to the atmosphere in the form of water vapour from the leaves of plants through the process of transpiration.
• The water vapours produced also goes into the atmosphere.
• Transpiration is the process by which plants and trees lose water out of their leaves into the air.
3. During the process of respiration in living plants and during the decay of dead plants water vapour is produced which also goes into the atmosphere.
4. Condensation– As the water vapour rises up, it gets cooled and it eventually condenses back into tiny droplets of liquid water.
5. These droplets are small enough to float in the air and eventually collect together to make a cloud. These clouds can be blown by the wind to move water to different parts of the earth.
6. Precipitation-As more and more water droplets form, they will join together to form bigger water drops in the clouds.
• These drops become too heavy to stay in the air and will fall to the earth as rain.
• In case of extremely cold weather, the water might freeze and fall as hail or snow.
• Any water that falls from the sky-rain, snow, sleet or hail is called precipitation.
7. Percolation and absorption: Some of the precipitation soaks into the ground.
• Some of the underground water percolates through the rock or clay layers to reach the underground water.
• This is called groundwater.
• On land the water is used by the plants, crops and trees to grow. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.
• In this way water was taken from the earth, returns to the earth and the water cycle is completed.
• Nitrogen makes up seventy-eight percent of the atmosphere, but most organisms cannot use this form of nitrogen, and must have the fixed form.
• Nitrogen is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins.
• Nitrogen is found in other biologically important compounds such as alkaloids and urea too.
• Nitrogen is thus an essential nutrient for all life-forms and life would be simple if all these life-forms could use the atmospheric nitrogen directly.
• The nitrogen cycle produces the fixed form of nitrogen these organisms need.
By lightning– During lightning, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen.
• These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain. These are then utilised by various lifeforms.
By bacteria– Molecular nitrogen is converted into nitrates and nitrites by free living bacteria or the bacteria like Rhizobium present in the root nodules of legumes.
• Special bacteria convert the nitrogen gas (N2) to ammonia (NH3) which the plants can use.
Nitrification– Nitrification is the process which converts the ammonia into nitrite ions and then into nitrates which the plants can take in as nutrients.
• Special kinds of bacteria are involved in this process which occurs naturally in the environment.
• The bacteria nitrosomonas and nitrococcus convert the ammonia into nitrite and then nitrobacter convert the nitrites into nitrates by oxidizing NO2 to NO3.
• All these bacteria reside in soil and are called as nitrifying bacteria.
• These soluble nitrates dissolve in soil water and are absorbed by the roots of plants.
• The nitrates and nitrites are used by plants to make amino acids which are then used to make plant proteins.
• The plant may be eaten by an animal, and its biomass used to produce animal protein.
Ammonification– When an animal or plant dies they release wastes from their bodies, nitrogen is released in the organic form.
• This organic nitrogen is converted into ammonium by fungi and bacteria through the process Ammonification.
• After all of the living organisms have used the nitrogen, decomposer bacteria convert the nitrogen-rich waste compounds into simpler ones.
• Urea and egested material is broken down by decomposers.
• This results in nitrogen being returned to the soil as ammonia.
• Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.
Denitrification- Denitrification is the final step in which the simple nitrogen compounds are converted back into nitrogen gas (N2), which is then released back into the atmosphere to begin the cycle again.
• When the ammonia is converted back into inert nitrogen, the process is called as denitrification.
• Bacteria are involved in this process which takes place in anaerobic conditions.
• Places like deep soils and deep water are the places without oxygen.
• Pseudomonas and Clostridium are responsible for the step of denitrification.
• These bacteria can also live in the places where there is availability of oxygen.
• Carbon is found in various forms on the Earth.
• It occurs in the elemental form as diamonds and graphite.
• In the combined state, it is found as carbon dioxide in the atmosphere, as carbonate and hydrogen carbonate salts in various minerals, while all life-forms are based on carbon-containing molecules like proteins, carbohydrates, fats, nitrogen-cycle in nature nucleic acids and vitamins.
• The endoskeletons and exoskeletons of various animals are also formed from carbonate salts.
The carbon cycle is the process by which carbon moves from the atmosphere into the Earth and its organisms and then back again.
Carbon enters the atmosphere as carbon dioxide from respiration (breathing) and combustion (burning)
• Carbon is incorporated into life-forms through the basic process of photosynthesis which is performed in the presence of Sunlight by all life-forms that contain chlorophyll.
• This process converts carbon dioxide from the atmosphere or dissolved in water into glucose molecules.
• Plants store and use this sugar to grow and to reproduce.
• Thus, plants help to remove carbon from the atmosphere.
• When plants are eaten by animals, their carbon is passed on to those animals.
• Since animals cannot make their own food, they must get their carbon either directly by eating plants or indirectly by eating animals that have eaten plants.
At the same time that some processes of nature are removing carbon from the air, other processes are adding more carbon to the air.
Respiration: Respiration is the next step in the cycle, and it occurs in plants, animals, and even decomposers.
• When plants and animals respire, glucose stored in the plants and animals are broken down to release CO2, water and energy.
• Through this process, CO2 is released back into the atmosphere.
Decomposition: As plants and animals die and decay or decompose (or when animals defecate and their waste materials decompose), the carbon found in them are released to the environment.
• When the decaying matter bodies get buried under the ground and are subjected to high pressures and other physical and chemical changes for millions of years, they change into fossil fuels.
Combustion: When the fossil fuels are burnt to provide energy for various needs like heating, cooking, transportation and industrial processes most of the carbon rapidly enters the atmosphere as carbon dioxide gas.
• In fact, the percentage of carbon dioxide in the atmosphere is said to have doubled since the industrial revolution when human beings started burning fossil fuels on a very large scale.
Movement of carbon from the atmosphere to the oceans: The oceans, and other water bodies, soak up about a quarter of the carbon dioxide gas from the atmosphere.
• However, this uptake process is slow.
• Similarly, under normal conditions, the release of carbon dioxide back into the atmosphere from the ocean is also at a very low rate.
Through these steps the total amount of carbon in the environment remains constant. There is no formation or demolition of carbon in this process and it only involves the movement of this element from one form to another.
• Oxygen is an important element to life on Earth.
• It is the most common element of the human body.
• It makes up about 65% of the mass of the human body.
• Most of this is in the form of water (H2O).
• Oxygen also makes up about 30% of the Earth and 20% of the atmosphere.
The Oxygen Cycle
Oxygen is constantly being used and created by different processes on planet Earth. All of these processes together make up the oxygen cycle. The oxygen cycle is interconnected with the carbon cycle.
Processes That Use Oxygen
Animals take in simple sugars (glucose) and oxygen and release carbon dioxide, water and energy.
• Decomposition: Is a minor part of the Carbon/Oxygen cycle
Decomposition is when any organic matter (plants, animals) breaks down chemically into all the simple elements that they are made of and these elements return back to the environment.
As plants and animals die and decay or decompose (or when animals defecate and their waste materials decompose), the carbon, oxygen, nitrogen, water, calcium etc. return to the soil and air during decomposition.
Processes That Produce Oxygen
Green plants/trees take in Carbon Dioxide and water using the chlorophyll in their leaves and energy from the sun they release Oxygen, sugar and water vapor.
• Sunlight – Some oxygen is produced when sunlight reacts with water vapor in the atmosphere.
Irrigation: Proper irrigation is very important for the success of crops. Ensuring that the crop gets water at the right stages during their growing season, can increase the expected yield of a crop. Different kinds of irrigation systems include wells, canals, rivers and tanks.
• Wells: These are of two types namely dug wells and tube wells.
In a dug well, water is collected from water bearing strata. Tube wells can tap water from the deeper strata. From these wells, water is lifted by pumps for irrigation.
• Canals: A canal system is a network created to move water from one source of water such as a stream or reservoir. The main canal is divided into branches that spread by through the fields so that water can be distributed everywhere.
• River lift system: In areas where canal flow is insufficient or irregular axle to inadequate reservoir release, the lift system is more rational. Water is directly drawn from the rivers for supplementing irrigation in areas close to rivers.
• Tanks: These are small storage reservoirs, which intercept and store the run-off of smaller catchment areas.
When the crop is in the field, it needs protection against weeds, insect pests and other diseases.
Weed: Weeds are unwanted plants in the cultivated field. For example, Xanthium (Gokhroo), Amaranthus (Chaulai), etc.
How weeds are harmful to main crop?
• They compete for food, space, light and essential nutrients thereby reduce the growth of the main crop.
• They promote the attack by crop pests and diseases by acting as alternate host to insects and microorganisms.
• During harvesting, weeds get mixed up with crop to lower down its quality.
Methods of weed control:
Weeds can be controlled by following ways:
• Manual removal of weeds.
• Adopting cultural methods like proper bed preparation, timely sowing of crops, intercropping and crop rotation.
• Using weedicides like 2,4- D (2,4-dichlorophenoxy acetic acid), MCPA (2-methyl, 4-chlorophenoxy acetic acid), Atrazine and Butachlor.
Insect pests: Insects which destroy or damage crop plants are called insect pests.
They affect overall health of the crop and reduce yield.
They attack the plants in following three ways:
• They cut the root, stem and leaves.
• They suck the cell sap from various parts of the plants.
• They bore into the stem and fruits.
Methods of insect pests’ control:
Using pesticides: The chemical used to eliminate pests are called pesticides. They include insecticides (for killing the insects), weedicides (for killing the weeds), rodenticides (for killing rats), and fungicides (for killing the fungi).
Using natural insecticides: Like neem, nicotine, pyrethrum, etc.
Storage of Grains
In order to make the seasonal foods available throughout the year, they are stored in safe storage.
During storage, they may get destroyed and wasted by following factors:
1. Biotic factors: The include living organisms like insects, birds, mites, bacteria, fungi.
2. Abiotic factors: They include non-living environmental like moisture contents, humidity of air, improper temperature etc.
Preventive measures to be used while storage of food grains are given below:
• Drying: The harvested food grains should be dried properly before storage.
• Cleaning and maintenance of hygiene before storage: The food grains should be properly cleaned and then filled in absolutely dry and clean gunny bags before keeping in godowns, warehouses or stores.
• Regular check on godowns: Godown, warehouses and stores should be properly cleaned, dried and repaired.
• Fumigation: Those pesticides which can destroy insects by forming toxic fumes are called fumigants and process of their use is called fumigation.
Fumigants may be solid, liquid or gaseous.
Soil fertility is one of the factors necessary for the soil to be able to sustain plant growth and optimize crop yield. Fertility is a combination of essential nutrients and a soil pH level that makes these nutrients available to plants.
Effective ways to improve soil fertility
1. Organic matters
• It provides additional nutrients and food for the microorganisms that live in your soil.
• Organic matters also hold soil particles into aggregates and improve the water holding capacity of the entire soil.
• Organic material used to help plants grow and fertilize them.
• They are basically good for the soil and plants because it supplies nutrients as well. However, it is recommended that it is better to mix compost with fertilizers rather than using it alone.
• It is a cropping pattern in which two or more crops are grown together in the same field.
• The main aim of this cropping method is to ensure some healed even if one of the crops fails to grow properly.
• The seeds of different crops are combined and planted together.
• Same fertilizers are used for all the crops.
• In this cropping method, different types of crops are chosen and irrigated on the same piece of land sequentially.
• The rotation of crops depends upon the soil, climate and water retention of the soil.
Activities that lead to improvement in the crop yield:
• Crop Variety Improvement
• Crop Production Improvement
• Crop Protection Management
Crop Variety Improvement
• In this approach, crops are selected on the basis of their characteristics. For instance, how well they can respond to fertilizers, can they produce high yield, how they resist diseases and so on.
Different methods of Crop Variety Improvement
1. Hybridisation - In this process, genetically different plants are crossbred.
They can be three types of crossing
• Inter varietal - Between two varieties of a plant
• Interspecific - Between two species belonging to same genus
• Inter Generic - Between species of different genus
2. Introduction of Gene - A gene that can provide the desirable characteristics to a crop are introduced in this process. As a result, we obtain genetically modified crops.
Factors on which Crop Yield Generally Depends
• The seeds used by the farmers - The seeds that are of similar variety are preferable.
• Climate or Weather Conditions - Crops that can sustain diverse climatic conditions are preferable.
• The duality of the Soil - Crops that can survive in a highly saline soil are preferable.
• Availability of Water - Crops should be grown as per the availability of water in the region.
The factors for which variety of improvement is done are:
• Higher yield: To increase the productivity of the crop per acre.
• Improved quality: The quality of crop products varies from crop to crop. E.g., the protein quality is important in pulses, oil quality in oilseeds, preserving quality in fruits and vegetables.
• Biotic and abiotic resistance: Biotic factors are the diseases, insects and nematodes while abiotic factors are the drought, salinity, waterlogging, heat, cold and frost which affect the crop productivity. Varieties resistant to these factors (stresses) can be improved to increase crop production.
• Change in maturity duration: shorter maturity period of crop reduces the cost of crop production and makes the variety economical. Uniform maturity makes the harvesting process easy and reduces losses during harvesting.
• Wider adaptability: It allows the crops to be grown under different climatic conditions in different areas.
• Desirable agronomic characteristics: It increases productivity, for example, tallness and profuse branching are desirable characters for fodder crops; while dwarfness is desired in cereals, so that less nutrients are consumed by these crops.
In agriculture, animal husbandry is a special field that deals with rising of the livestock in a controlled, selective environment by providing them with the right care so that they can stay healthy and disease free.
There is a need to improve livestock production because the population of India is tremendously increasing. This means an increase in demand for eggs, milk and meat.
Animal husbandry includes the following:
- Cattle Farming
Cattle are used for two reasons –
• They provide milk
• They work as draught labour in the fields
Milch Animals: Animals that provide milk are called Milch Animals.
Draught Animals: Animals that work in the fields for irrigation, carting and tiling are called Draught Animals.
To Increase the milk production in cattle
• Milk production can be enhanced by increasing the lactation period in the cattle.
• Crossbreeding of foreign breeds and local breeds can provide cattle with qualities of increased lactation period and resistance to diseases.
• Shelters of the cattle should be kept neat and clean in order to keep the cattle healthy.
• The cattle should be kept clean and should be provided with a covered shelter that can protect them from harsh weathers.
• The floor of the shelters to be kept a dry and clean
- 2.Poultry farming
Poultry farming includes different kinds of domesticated birds. Different types of poultry are:
It is mainly done for:
1. getting eggs through layers
2. getting chicken meat through broilers
Examples of Poultry birds:
• Indigenous breeds: Aseel, Burosa
• Foreign breeds: Leghorn, Black Minorca
Crossbreeding is a way to achieve this. Generally, foreign breeds of chicken are crossed with Indian breeds to achieve high quality. It thus has better traits such as:
• Increase in a number of chicks.
• They can tolerate high temperatures.
• They do not require much maintenance
• They can survive cheap diets
Egg and broiler production
• They need a diet with a high quality of Vitamins A and K, proteins and fats.
• They need special care to maintain feathering and avoiding death.
• Proper hygiene and temperature conditions should be provided to the broiler chicken.
• They do not require such nutrient-rich diet.
• They just need a controlled diet.
• The layers require more space and lightning as compared to the broilers.
Disease Control methods should also be adopted against the diseases that are generally caused by bacteria, fungi and parasites in broilers and layers. Disinfectants can be sprayed regularly to avoid such diseases. Sometimes deficiency of nutrition can also need to diseases. Vaccination is a good way to protect the poultry fowl from diseases.
Fish can be obtained in two ways:
• From Natural Resources - Capture Fishing
• From Fish Farming - Culture Fishing
• Marine fishes are caught using fishnets and mechanical capturing techniques.
• The main source of marine fishes is marine water or salt water.
• Generally, large numbers of fishes can be captured at a time through mariculture.
• Fishes found in lakes, ponds, lagoons and rivers are captured.
• The main source of Inland fisheries is freshwater and brackish water.
• The yield is not as high in these sources hence large numbers of fishes are captured through aquaculture.
• For Example, silver carp, common carp
Composite fish culture
• In a composite fish culture, fishes are grown along with rice crop in the paddy fields.
• In this method, a combination of 5 - 6 local as well as foreign fishes is grown in a single pond.
• Such species are selected because they have different food habits and would not compete for the food with each other.
• Some of them are surface feeders; some are middle zone feeders while others are bottom feeders.
• They would rather eat all the food in the pond.
• As a result, the fish yield in the pond increases
For Example, Catlas (surface feeders), Rohu (middle feeders), Mrigal (bottom feeders), Common Carps (bottom feeders), Grass Craps (aquatic weed eaters) are often grown together in composite fish culture.
Bee farming is performed in bee farms or apiaries. Many farmers perform beekeeping as a means of generating additional income because:
• Honey is a widely used product
• Bee farming is not very expensive
• They also generate wax along with honey
Bees used for commercial and honey production
• Apis Cerana Indica - Indian bee
• A. Dorsata - The rock bee
• A. Florae - The little bee
• A. Mellifera – Italian variety of bee
Why Italian bees are popular in Bee farming?
• They produce large amounts of honey.
• They do not sting much.
• The breeding period in Italian bees is long.
Factors that determine the quality of honey
• Along with the choice of selection of the bee species, the flowers decide the quality, quantity and taste of the honey produced.
• There should also be enough pasturage or availability of flowers to the bees so that they can collect enough nectar and pollen.