Natural Resources Class 9 Science Exam Questions

Exam Questions Class 9

Please refer to Natural Resources Class 9 Science Exam Questions provided below. These questions and answers for Class 9 Science have been designed based on the past trend of questions and important topics in your class 9 Science books. You should go through all Class 9 Science Important Questions provided by our teachers which will help you to get more marks in upcoming exams.

Class 9 Science Exam Questions Natural Resources

Class 9 Science students should read and understand the important questions and answers provided below for Natural Resources which will help them to understand all important and difficult topics.

1 Mark Questions

Question. Name a pollution free source of energy.
Answer. Solar, Wind, Hydro, and Nuclear are all emission free, and therefore do not produce “pollution” but all energy sources will create waste.

Question. What is the fate of nitrogen gas that goes inside the lungs along with oxygen during breathing?
Answer. Although most of Earth’s atmosphere is composed of nitrogen, the human body cannot utilize this gas, so it is simply exhaled.

Question. What is called the crust of the earth?
Answer. The outermost layer of our Earth is called the crust and the minerals found in this layer supply a variety of nutrients to life-forms.

Question. What are the main resources on the Earth ?
Answer. The main resources on the Earth are the land, the water and the air.

Question. What factors decide the sustainability of life forms in a region?
Answer. i) The availability of water
ii) Temperature
iii) Nature of soil

Question. What is strip- cropping?
Answer. Strip-cropping means planting of crops in rows or strips to check flow of water and soil pollution.

Question. What are the main substances of biogeochemical cycles?
Answer. The main substances of biogeochemical cycles are carbon, oxygen, nitrogen, phosphorus, calcium, and water etc.

Question. What is the role of soil in agriculture?
Answer. The soil refers to the loose surface of the earth’s crust. Soil is the medium for growth of all plants. It provides physical supports and nutrients and also the sufficient quantities of air and water for growth of plants.

Question. Name the two gases given out by burning of fossil fuels, which dissolves in rain to form acid rain.
Answer. Sulphur dioxide (SO2) and oxides of nitrogen (NOx).

Question. Write the two biotic components of the biosphere.
Answer. The biotic components of biosphere are plants, animals and microorganisms.

2 Marks Questions

Question. How is CO fixed in the atmosphere?
Answer. It is fixed in many ways:
(a) During the process of respiration in humans and animals, carbon dioxide released into the atmosphere as a by-product
(b) Decomposition is the largest source through which carbon is returned to the atmosphere as carbon
(c) Weathering of rocks.
(d) By burning the fossil fuels
(e) From Volcanic eruptions

Question. What factor decides the rain patterns? Which are the winds that bring about rain in most parts of India?
Answer. i)Rainfall patterns are decided by the prevailing wind patterns
ii) a) South-west monsoons.
b) North-east monsoons.

Question. Write in detail what happens when water gets polluted
Answer. When water gets polluted, then following events happen:-
(a) Undesirable substances get added to water-bodies which may cause cholera.
(b) Desirable substance may get removed from water-bodies and dissolved oxygen in water which is important for aquatic life and endangering aquatic life.

Question. What is eutrophication ?
Answer. The excessive growth of phytoplankton in water bodies because of discharge of sewage and detergents in it brings about a reduction in dissolved oxygen which affects other aquatic organisms. This is called eutrophication.

Question. How can you say that rivers carry many nutrients from the land to the sea?
Answer. Water is capable of dissolving a large number of substances. As water flows through or over rocks containing soluble minerals, some of them get dissolved in the water. Thus rivers carry many nutrients from the land to the sea, and these are used by the marine organisms

Question. Name the forms in which Nitrogen is present in living things:
Answer. (i) Nitrogen is a constituent of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins.
(ii) Nitrogen is found in other biologically important compounds such as alkaloids and urea too.

Question. What is smog?
Smog is a combination of smoke and fog. This is formed due to the condensation of fog on the carbon particles present in the smoke that is produced due to the combustion of domestic fuels and industrial fuels like coal and petroleum. It lowers the visibility during the winter season and is an indication of air pollution.

Question. Do we ever come across phenomenon of greenhouse effect in daily life?
Answer. Yes, we do come across this phenomenon in our daily life. One example of the greenhouse effect that most of us experience in everyday life is the warming of a car’s interior when the vehicle is left out in the sun. 

Question. What is the greenhouse effect?
Answer. The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and reradiated by greenhouse gases thereby warming the Earth enough to support life.

Question. What is biosphere?
Answer. The life-supporting zone of the earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible is known as the biosphere. It accommodates several types of living organisms which remain dependent on natural resources. The biosphere ranges between 6km above sea level and 10km below sea level.

Question. What are aerosols? How are these dangerous?
Answer. Aerosols are certain chemicals like fluorocarbons released in the air either naturally or by human activities in the form of mist or vapour. Fluorocarbons deplete the ozone layer in the atmosphere are emitted by jet aeroplanes, deodorant sprays etc.

Question. What is ozone hole?
Answer. The ozone hole is not technically a “hole” where no ozone is present, but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic that happens at the beginning of Southern Hemisphere spring (August–October).

Question. Why is humus considered to be the major factor in deciding the soil structure? What is the role of earthworms in increasing the quantity of humus?
Answer. (i) Humus is a major factor in deciding the soil structure because it causes the soil to become more porous and allows water and air to penetrate deep underground.
(ii) Earthworms feed on the humus and increase its fertility.

Question. State in brief the role of photosynthesis and respiration in carbon-cycle in nature.
Answer. The role of photosynthesis and respiration in Carbon cycle in nature are as follows:
(a) Plants convert the carbon in atmospheric carbon dioxide into carbon-containing organic compounds, such as sugars, fats, and proteins.
(b) Cellular respiration (in plants and animals)requires oxygen (which is the by-product of photosynthesis) and it produces carbon dioxide, which is used in photosynthesis. In this way, photosynthesis and cellular respiration are linked in the carbon cycle.

3 Marks Questions

Question. State two factors responsible for weathering of rocks.
Answer. Two factors responsible for weathering of rocks are:
(a) Climate conditions- It includes the meteorological elements effect on rocks such as moisture, temperature, and wind and air pressure
(b) Topography and vegetation- Topography directly effects weathering by exposing rocks to the temperature or sun and wind. The elevated areas will be affected more and low level areas will be affected less
(c) Composition-There are certain elements which are included in rock composition. Some rocks will weather quickly and some slowly e.g. acidic rocks weather more quickly than basic ones. Surface covered by the vegetation are protected from weathering but bare surfaces are weathered to great extent.

Question. How addition of undesirable substances and change in temperature affect the water life?
Answer. The poisonous things like pesticides can kill the fish or other water creatures. The nutrients in fertilizers cause rapid growth of algae, also known as an algal bloom. The algal bloom causes the deficiency in oxygen in the water bodies while the change in temperature will affect breeding and development of young ones of aquatic organism.

Question. Why does water need conservation even though large oceans surround the land masses?
Answer. Water conservation is important because we need water for many essential activities. About three fourth of Earth consists of water, but only 1% of it is freshwater. It is this freshwater which we can utilise for daily use. As water resources are not judiciously used, these are getting depleted. This will lead to the time when there will be no water. If water conservation is carried out seriously, this will help to preserve wildlife water habitats and the need of building dams, etc. It will also help to ensure water availability for future generations.

Question. How do the rivers from land, add minerals to sea water?
Answer. Water is capable of dissolving large number of substances. As water flows over the rocks that contain soluble minerals, some of them get dissolved in the water. Thus rivers carry many nutrients from land to sea. These salts stay in the sea because no water flows out of the sea.

Question. How can we prevent the loss of top soil?
Answer. The uppermost layer of soil is very fertile and rich in humus. The main threat to top soil is soil erosion. Soil erosion is loss of soil due to wind or water flow. Loss of top soil can be prevented by stopping soil erosion by following methods:
(i) Afforestation
(ii) Strip cropping
(iii) By following crop rotation to maintain the fertility of soil.
(iv) Proper drainage and irrigation arrangements.

Question. Why is replenishment of soil essential? Describe two natural ways of soil replenishment.
Answer. Some nutrients of the soil get depleted by growing the same crop year after year in the same field. So, replenishment of soil is essential to keep it fit for further cultivation.
Two natural ways of soil replenishment are-
(i) Crop rotation.
(ii) By leaving the agricultural land uncultivated (fallow) for one or two seasons so as to allow the soil to regain its richness.

Question. The heaps of solid wastes are a menace. Give two reasons.
Answer. The heaps of solid wastes are a menace because-
(i) The solid wastes release harmful gases into the environment which pollute the air of surrounding areas.
(ii) The solid wastes litter in the surrounding areas choking the sewage system
(iii)The unpleasant smell coming out of the wastes also pollute the environment.

Question. Soil formation is done by both abiotic and biotic factors. List the names of these factors by classifying them as abiotic and biotic?
Answer. Soil formation by biotic and abiotic factors:
Soil formation occurs due to five important factors. Differences in soil particles within and between regions are a result of the interaction between these factors.
(i) Abiotic factors: Rocks (parent material), rain, temperature, slope and elevation, time, etc.
(ii) Biotic factors: Vegetation, microbes, soil organisms, animals and human beings

Question. What is biogeochemical cycle ?
Answer. A biogeochemical cycle or nutrient cycle is the cyclic flow of nutrients between the biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. The plants and animals that live and then die are the bio part; the earth that they decompose into comprises the geo part; and
the process by which organic matter returns to the chemical elements in the earth is explained by the chemical part. There are four biogeochemical cycles namely carbon cycle, oxygen cycle, nitrogen cycle and phosphorous cycle, and each of them returns to the earth important elements that are required in living organisms.

Question. Name the two chemicals present in the living organisms having carbon, hydrogen and oxygen as main constituents. State their main function.
Answer. Proteins and Nucleic acid contain carbon, hydrogen and oxygen. The main role of nucleic acids is to store information that is used to make proteins. Nucleic acids come in two main forms: deoxyribonucleic acids, also known as DNA, and ribonucleic acids, also known as RNA. The main function of DNA is to store the genetic information that cells in the body need to function. RNA, on the other hand, plays an important role in converting the information from DNA into proteins. The role of proteins in cell is that are responsible for doing most of the work that occurs in cells. They also are needed to maintain the structure of cells and are critical for the function and regulation of all of the body’s tissues.

Question. Why can’t the living organisms use atmospheric nitrogen directly?
Answer. Although the majority of the air we breathe is nitrogen(N ), most of the nitrogen in the atmosphere is unavailable for use by organisms. This is because the strong triple bond between the N atoms in N2 molecules makes it relatively inert. In fact, in order for plants and animals to be able to use nitrogen, N2 gas must first be converted to more a chemically available form such as ammonium (NH4+), nitrate (NO3), or organic nitrogen (e.g. urea -(NH2)2CO).

Question. What are the various forms of carbon found on earth?
Answer. 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, nucleic acids and vitamins. The endoskeletons and exoskeletons of various animals are also formed from carbonate salts.

Question. Describe carbon-cycle in the biosphere.
Answer. (i) Carbon Cycle
In the abiotic environment, carbon is present in four forms:
(a) As carbon dioxide in the atmosphere or air (about 0.03 – 0.04%),
(b) As dissolved carbon dioxide or carbonic acid and bicarbonates in water or hydrosphere,
(c) As fossil fuels like coal, petroleum and natural gas, and
(d) As carbonates and graphite in the rocks.
The basic movement of carbon is from the atmosphere- 
During photosynthesis, plants take in carbon dioxide from the atmosphere to synthesize organic compounds. These organic compounds enter the food chain as food and reach animals in successive trophic levels.

Question. How is prediction of weather possible?
Answer. Weather of a place is determined by many elements like speed and direction of wind, temperature, air pressure, rainfall, relative humidity and oceanic features. All these information’s are collected by meteorological department through remote sensing and weather forecasting satellites which are then transformed into a weather report. This collective information helps us to predict the weather of a place. 

Question. What is meant by air pollution?
Answer. Air pollution is defined as the presence of a contaminant in the atmosphere in a concentration large enough to injure human, plant and animal life. The presence of gaseous pollutants such as oxides of sulphur, nitrogen and carbon, hydrocarbons and particulate pollutants such as dust, smoke, mist spray and fume causes air pollution.

Question. What is capillary water? Can plants draw capillary water from soil?
Answer. Capillary water is the water that remains in the soil after the water drains; it permits plants to survive through periods of drought. Capillary water is held in the capillary pores (micro pores). Capillary water is retained on the soil particles by surface forces. It is held so strongly that gravity cannot remove it from the soil particles. The molecules of capillary water are free and mobile and are present in a liquid state. Capillary water is, therefore, known as available water. Trees ‘drink’ from capillary water. Their instrument to drink from the capillary water is the primary root.

Question. What is algal bloom?
Answer. Algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwaters as well as in marine environments.
Harmful algal blooms can:
 Produce extremely dangerous toxins that can sicken or kill people and animals
 Create dead zones in the water
 Raise treatment costs for drinking water

Question. Why do people love to fly kites near the seashore?
Answer. People love to fly kites near the seashore because in coastal areas during daytime, the air above land gets heated faster and starts rising creating a low pressure above the land surface. The low pressure zone is filled in by cooler air from the ocean surface. This gives rise to the sea breeze. This sea breeze
helps in the flying of kites to great heights.

Question. What are the factors that affect the movement of air?
Answer. The various other factors also influence movement of air arei)
Uneven heating of atmosphere in different regions of the earth.
ii) The rotation of the Earth
iii) The presence of mountain ranges in the paths of the wind
iv) Topography of the region (sand, land, water etc) through which air/wind passes.

Question. How are clouds formed?
Answer. A large amount of water evaporates and goes into the air some amount of water vapour also get into the atmosphere because of various biological activities. This air also gets heated. The hot air rises up carrying the water vapour with it. As the air rises, it expands and cools. This cooling causes the water vapour in the air to condense in the form of tiny droplets around dust and other suspended particles in the air. When billions of these droplets come together they become a visible cloud.

Question. How do forests play an important role in maintaining water cycle?
Answer. Forests play an important role in maintain the water cycle.
i) The roots of plants/ trees bind the soil tightly and help in the percolation of water in the soil and thus add to the water table.
ii) Water is absorbed back by roots and is in turn lost into the atmosphere by transpiration.
iii) These vapours condense and form clouds.
iv) When clouds become heavy with water droplets it precipitates in the form of rain, snow, sleet etc Thus, plants maintain water cycle by passing moisture from soil to the atmosphere by transpiration.

Question. What is humus? What is its function in the soil?
Answer. (a) Humus is a dark coloured colloidal material that constitutes the organic components of the soil. It is formed by the decomposition of plant and animal remains.
(b) Humus is the major factor in deciding the soil structure because: Humus usually increases the ability of the soil to resist erosion. First, it enables the soil to hold more water. Even more important is its effect in promoting soil granulation and thus maintaining large pores through which water can enter and percolate downward. Humus provides a reservoir for the plant nutrients available in the soil for balanced plant growth.

Question. How do living organisms influence the formation of soil?
Answer. Living organisms also influence the formation of soil.
1. The lichen which grows on the surface of rocks release certain substances that erode the rock surface into powder and form a thin layer of soil. Other small plants like moss, now can grow on this surface and cause the rock to break up further.
2. The roots of big trees sometimes grow into cracks in the rocks and as the roots grow bigger, the crack is forced bigger resulting in the breaking of rocks into small pieces.

Question. Lichens are called pioneer coloniser of bare rock. How can they help in formation of soil?
Answer. A bare rock consists of solid surface or very large boulders and there is no place for rooting plants to colonize. The thalli of lichens can adhere to the surface of rock and absorb moisture from atmosphere. Therefore, these colonize the bare surfaces of rocks first. These lichens produce acids which corrode the rock and their thalli collect windblown soil particles with them that help in formation of a thin film of soil. When these lichens die their thalli are decomposed to add humus. This promotes soil formation.

Question. What are the biotic and abiotic components of the biosphere ?
Answer. Biotic component are the living organisms of the ecosystem. These are obtained from the biosphere and are capable of reproduction. Examples of biotic factors are animals, birds, plants, fungi, and other similar organisms.
Abiotic factors refer to non-living physical and chemical elements in the ecosystem. Abiotic resources are usually obtained from the lithosphere, atmosphere, and hydrosphere. Examples of abiotic factors are water, air, soil, sunlight, temperature, light, minerals etc.

Question. What is the role of atmosphere in maintaining temperature of the earth fairly steady?
Answer. Our atmosphere behaves like a green house that absorbs the radiations that enter inside it and doesn’t allow all the radiations to escape from this green house.
During daytime, it absorbs most of the harmful radiations like the ultraviolet rays coming from the sun. Dust particles, water vapour and clouds reflect back excessive heat into the space. This allows only right amount of heat and light to reach the earth the earth. Atmosphere prevents sudden increase in
temperature during daytime. Air being a bad conductor of heat, slows down the escape of heat from the surface of the earth into outer space during night time. In this way, the atmosphere keeps the average atemperature of the earth fairly constant during daytime and even during the course of the whole year.

Question. What is the importance of atmosphere for the existence of life?
Answer. Atmosphere is essential for life for several reasons. Some of these reasons are:
(i) Oxygen that is required for the survival of every living organism is present in the atmosphere.
(ii) Atmosphere works as an insulator; it keeps the average temperature of the earth fairly constant during the day and night by preventing escape of heat into outer space.
(iii) Atmosphere also acts as protective blanket for the Earth. It absorbs most of the harmful radiations such as ultraviolet (UV) radiations coming from the Sun. It results in the Earth receiving just the right amount of heat and sun’s rays, which helps in the climate control and allows the living organisms to exist.

Question. Why should not the fertilisers and pesticides be used in large amount?
Answer. Fertilisers and pesticides should not be used in large amount because- 
• Too much of it can be leached out of the soil into groundwater, or eroded from the surface into rivers and thereby polluting the water bodies. 
• Certain pesticides used in excess can actually contaminate the crop upon which they are applied and could poison livestock or people.
• They are non- biodegradable by nature.

Question. Name some of damaging effects of the ultraviolet rays on the animal and plant life on earth. The ultraviolet rays cause:
Answer. (a) It causes sunburn on human skin and cataracts in our eyes.
(b) Increases plants’ susceptibility to disease.
(c) Induces skin cancer by causing mutation in DNA and suppressing certain activities of the immune system
(d) In plants, UV impairs photosynthesis in many species

Question. The AC of your car was not working properly for last couple of days. You took the car to a nearby garage and asked the mechanic to refill the refrigerant. After checking, the mechanic advised you to repair the leak in the AC. You were in a hurry and hence, decided to postpone the repairing part and asked the mechanic to refill the refrigerant only. However, your father did not agree to refill the refrigerant in a leaked system.
(a) What value is shown by your father?
(b) How can you and your family help in protecting the ozone layer?
(c) How is ozone produced in the atmosphere?
Answer. (a) The father displays the responsibility of a responsible citizen in protecting the environment from pollution.
(b) (i) Ensure that refrigerant you recover from air conditioners, refrigerators or freezer during servicing is not “vented” or released to the atmosphere.
ii) Buy products (aerosol spray cans, refrigerators, fire extinguishers, etc.) that are labelled “ozone friendly” or “CFC free”.
(c) Ozone is produced naturally in the stratosphere when highly energetic solar radiations strikes molecules of oxygen and cause the two oxygen atoms to split apart. If a freed atom collides with another oxygen atom, it joins up forming ozone.

Question. What is greenhouse effect? List two greenhouse gases. State the ultimate effect of increase in greenhouse gases in the environment.
Answer. The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re radiated by greenhouse gases thereby warming the Earth enough to support life. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs). The rapid increase in greenhouse gas concentrations in the atmosphere has led to the enhanced greenhouse effect, which is when too much heat is trapped on Earth, resulting in an overall increase in global temperatures. Rising temperatures on Earth have produced severe changes in weather patterns, such as hotter summers, colder winters and stronger storms, like hurricanes and tornadoes. Increasing global temperature will also lead to a rise in sea levels as the glaciers and polar ice caps melt.

Question. (a) List two ways by which carbon dioxide is ‘fixed’ in the environment.
(b) Name two diseases caused due to an increased content of pollutants in the air produced due to the burning of fossil fuels.
Answer. (a) Carbon dioxide is fixed in the two following ways:
(i) By the process of photosynthesis in plants.
(ii) Many marine animals use carbonates dissolved in sea-water to make their cells.
(b) Diseases caused due to an increased content of pollutants in the air produced due to the burning of
fossil fuels are- ophthalmic problems, skin injuries, gastro-intestinal, cardio-vascular and respiratory diseases and some types of cancer.

Question. What is the role of the atmosphere in climate control?
Answer. The atmosphere plays an important role in temperature control. Atmosphere covers the Earth, like a blanket. Air is a bad conductor of heat. The atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the course of the whole year. It also prevents the sudden increase in temperature during the daylight hours. Moreover, during the night, it slows down the escape of heat into outer space.

5 Marks Questions

Question. Ishita went to her grandmother’s home in her holidays. In grandmother’s home, she noticed that the marbles used in balcony and on approach road from the gate to car garage has become yellow. Her grandmother told the problem started after establishing of a petroleum refinery in their locality. 
Read the above passage and answer the colourisation of marble?
(a) What is the connection of refinery to yellow colourisation of marble?
(b) State other harmful effects of air pollution.
(c) What values you have learnt from the given passage?
(a) Smoke released by the refinery contains oxides of nitrogen and sulphur. These gases dissolve in rain water causing acid rain. The acid rain contains traces of acids which affected the marble floor. This acid rain leads to the erosion of white marble. The colour of floor is also affected by acid rain i.e. it becomes yellowish.
(b) Harmful effects of air pollution are —
(i) Air pollution affects the respiratory system of living beings and causes bronchitis, pneumonia, asthma and lung cancer.
(ii) Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and sulphur. Not only the inhalation of these gases is dangerous, they also dissolve in rain to produce acid rain. Acid rain destroys the small plants and crops.
(c) From the given passage, I have learnt that factories and industries in an area play major role in air pollution. These should be far from human inhabited areas. I have learnt the value of concern and care for environment from this passage.

Question. (a) What are the consequences of Global warming?
(b) Draw a labelled diagram to show water cycle in nature.
(c) Why is water essential to life?

Answer. (a) Harmful effects of global warming:
(i) Warmer waters and more hurricanes: As the temperature of oceans rises, so will the probability of more frequent and stronger hurricanes.
(ii) Increased probability and intensity of droughts and heat waves: Although some areas of Earth will become wetter due to global warming, other areas will suffer serious droughts and heat waves.
(iii) Polar ice caps melting: The ice caps melting are a four-pronged danger. It will raise sea levels.
(iv) More floods: Flooding represents one of the most dangerous hazards to human settlements and As the climate changes, a warming of the seas creates ‘thermal expansion’. This is where warm water begins to take up more space than cool water, making the sea’s surface level increase.

(c) Organisms need water because it plays a vital role in the reaction that takes place within organism’s cells and body. It acts as a universal solvent, providing a medium for the chemical reactions to occur. Substances are also transported from one part of the body to the other in dissolved state. Therefore, it is not necessary for organisms to maintain a distinct level of water within their bodies to stay alive.

Question. A few years ago, after Ganesh Chaturthi celebrations, lakhs of dead fishes were found near sea
Answer. shore of Juhu in Bombay. Similarly, after immersion of idols of God and Goddess at other festivals, such as Durga Puja, water of rivers and sea becomes highly polluted. That causes suffocation of aquatic animals like fishes.
Answer the following questions based on above information:
(a) What is the cause of high water pollution?
(b) What are your suggestions to avoid this pollution?
(c) What values students depict by giving positive suggestions?
a) Idols which are immersed in river or sea are made of Plaster of Paris and painted with toxic chemicals paints which contain lead, iron, arsenic, etc. Accessories used during the worship that are dumped along with the idol are non biodegradable. All these cause high water pollution.
(b) (1) Idols to be immersed should be made of naturally occurring clay instead of Plaster of Paris which doesn’t occur naturally. Idols made out of naturally occurring clay dissolve within hours of immersion in water, Plaster of Paris idols may take anywhere between several months to years to fully dissolve.
(2) Immersing the idol in a water tank constructed by the government, instead of directly into natural water bodies.
(3) Use of toxic colour to paint idols should be banned.
(c) – Protecting the environment from pollution
– Awareness about the environmental issues faced by our country
– Preservation of biodiversity of aquatic beings.

Question. What are the sources of water pollution?
Answer. The main sources of water pollution are;
i ) Sewage and other wastes: Sewage is the waste water from homes, animal houses or food producing plants. Sewage includes human excreta, paper, cloth pieces, soap and detergents etc, wastes of rural areas, towns and cities are dumped into ponds, lakes, rivers etc. due to large amounts of dumped waste, water loses its self purifying ability and thus becomes unfit for human consumption
ii) Industrial effluents: Effluents from breweries, tanneries , dying textiles, paper and pulp mills, sugar mills etc., contain a variety of inorganic and organic and organic pollutants such as oils, greases, plastics , plasticizers, DDT, acids, alkalies, dyes etc., are flown into rivers. These cause water pollution.
iii) Agricultural discharges: These include chemicals of fertilizers and pesticides. These chemicals along with wastes are washed off through rainfall, drainage and irrigation etc, and eventually enter into lakes, rivers etc, thereby disturbing the natural ecosystem. Fertilizers used on crops, seep into ground water making it unfit for human consumption.
iv) Industrial wastes: Heat and radioactive substances are the pollutants of thermal and nuclear plants. Nuclear power plants are located close to water bodies. The waste water released from these industries affects the aquatic life causing death.

Question. (a) What makes biosphere dynamic but stable system?
(b) Draw a labelled diagram to show the oxygen cycle in nature.
Answer. (a) Biosphere has biotic (living) and abiotic (non-living) components. The biotic or living components include plants, animals and microbes living on the earth. Abiotic components are land water and air. A constant interaction between the abiotic and biotic components of the biosphere results in the transfer of food and energy, which makes it a dynamic but stable system.
(b) Oxygen cycle in Nature:

Question. What is soil? How is it formed? State the major factors that decide the structure of a soil. What role does it play?
Answer. Soil is a mixture of broken rocks and minerals, living organisms, and decaying organic matter called humus. Humus is dark, soft and rich in nutrients. Soil also includes air and water.
Soil is formed by the following actions:
(a) Action of sun: The sun causes the heating of rocks during the day which causes them to expand. Then, these rocks cool down during night time leading to their contraction. Since, all parts of the rocks do not expand and contract at the same rate; it results in the formation of cracks on the rocks. Finally, these huge rocks break down into smaller pieces.
(b) Action of wind: Strong winds and storms also erode the rocks. The strong wind carries small rock pieces and sand from one place to another like water.
(c) Action of living organism: Roots of plants break down the rocks. Similarly, Lichens grow on the surface of rocks. These lichens release certain chemical that causes the rock surface to powder down to form a thin layer of soil.
(d) Action of water: (i) Water gets into the cracks in the rocks, when this water freezes, it causes the cracks to widen. (ii) Flowing water wears away even hard rocks over long periods of time. Fast flowing water often 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 and smaller particles, resulting in the formation of soil. The type of soil is decided by the average size of particles found in it and the quality of the soil is decided by the amount of humus and the microscopic organisms found in it. The nutrient content of a soil, the amount of humus present in it and the depth of the soil are some of the factors that decide which plants will thrive on that soil. The quality of the topsoil is an important factor that decides biodiversity in that area.

Question. (a) Difference between biodegradable and non biodegradable substances.
(b) How is acid rain causing harm to Taj Mahal?
(c) What is smog?
(a) Biodegradable and non-biodegradable substances

(b) Taj Mahal is situated in Agra. The air in this place contains serious levels of sulphur and nitrogen oxides. This is due to the large number of power plants and industries set up around this area. All these led to acid rain. Acid rain reacted with the marble (calcium carbonate) of Taj Mahal and makes it yellow in colour.
(c) Smog is a combination of smoke and fog. This is formed due to the condensation of fog on the carbon particles present in the smoke that is produced due to the combustion of domestic fuels and industrial fuels like coal and petroleum. It lowers the visibility during the winter season and is an indication of air pollution.

Natural Resources Class 9 Science Exam Questions

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