Class 9 Science Chapter 14 Natural Resources
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Natural Resources
Answers to Questions Within the Lesson(1)
Q1. How is the atmosphere of the Earth different from that of Venus and Mars?
Ans: The Earth’s atmosphere contains a higher amount of oxygen and a lower amount of carbon dioxide. It provides a suitable environment for living organisms to survive.
On the other hand, the atmospheres of Venus and Mars contain almost no oxygen and a very high amount of carbon dioxide (about 95–97%), which is the main component. Such atmospheres are not suitable for the survival of life.
Q2. How does the atmosphere act like a blanket?
Ans: The atmosphere protects the Earth in various ways. It contains a mixture of different gases. Among them, ozone absorbs the harmful ultraviolet rays coming from the Sun. The atmosphere also helps in maintaining a stable temperature on Earth. Therefore, it is said that the atmosphere acts like a blanket.
Q3. How is wind produced?
Ans: During the day, the heat of the Sun warms the air and water bodies, causing evaporation and formation of water vapour. Due to heating of land and water, the lower layer of the atmosphere becomes warm. As temperature increases, the air becomes lighter and creates a low-pressure area. In cooler regions, air pressure is higher, so air moves from high-pressure areas to low-pressure areas. This movement of air creates wind.
Q4. How are clouds formed?
Ans: During the day, the Sun heats water bodies and a large amount of water evaporates into the atmosphere. This water vapour gradually cools and condenses into tiny droplets of water, which we see as clouds.
Q5. List any three activities that cause air pollution.
Ans: Fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burned, they form sulphur oxides and nitrogen oxides, which cause problems in breathing. Some of these oxides mix with rainwater and fall as acid rain.
Burning of fossil fuels also increases the amount of suspended particulate matter in the air. These particles may include unburnt carbon or hydrocarbons, which pollute the air.
When the level of pollutants increases, the sky appears smoky, especially in the evening. This is called smog. Increased air pollution can cause allergies, cancer, and lung diseases.
Answers to Questions Within the Lesson(2)
Q1. Why do living organisms need water?
Ans: The availability of water not only determines the number of organisms living in a particular region but also its biodiversity. Water is essential for survival. It is a medium in which all substances required for metabolic activities in our body are dissolved. In this dissolved state, substances are transported from one part of the body to another as needed.
Q2. What are the sources of safe drinking water in cities, towns, and villages? Where do you live?
Ans: The sources of safe drinking water in cities, towns, and villages include water supply systems through pipelines from water sources. The answer to where you live should be written by yourself.
Q3. Which activities can cause water pollution?
Ans: The use of chemical fertilizers and pesticides in agricultural fields leads to their mixing with water. Rainwater washes these substances into rivers, lakes, and other water bodies. Waste generated daily in urban households and effluents from industries and factories are often discharged into rivers and lakes. In some industries, water is used for cooling machines, and after use, hot water is released back into rivers, increasing water temperature. Excess water released from hydroelectric projects also affects water bodies. Surface water gets heated easily by sunlight, while deeper water remains cooler. All these activities lead to water pollution.
Answers to Questions Within the Lesson(3)
Q1. How is soil formed?
Ans: Soil is formed when the upper layer of hard rocks breaks down into small particles due to physical, chemical, and biological processes. Over time, these particles turn into soil.
Q2. What is soil erosion?
Ans: The removal of the top layer of soil by natural factors is called soil erosion.
Q3. What measures can be taken to prevent soil erosion?
Ans: The following measures can be taken:
(i) Planting trees.
(ii) Building strong embankments along riverbanks to prevent erosion.
(iii) Ensuring proper drainage of water over land.
Answers to Questions Within the Lesson(4)
Q1. In what forms is water found in the water cycle?
Ans: In the water cycle, water is found in three states: liquid, gaseous, and solid. It exists as surface water, water vapour, clouds, and rain.
Q2. Name two compounds containing oxygen and nitrogen that are important for biological processes.
Ans: Two such compounds are nitrite (NO2₂-) and nitrate (NO3₃-).
Q3. Mention three human activities that increase the amount of CO2 in the air.
Ans: (i) Burning of fossil fuels.
(ii) Deforestation.
(iii) Excessive use of vehicles leading to increased carbon dioxide in the air.
Q4. What is the greenhouse effect?
Ans: Certain gases present in the atmosphere trap heat on the Earth. As the amount of these gases increases, the Earth’s temperature rises. This phenomenon is called the greenhouse effect.
Q5. In which two forms is oxygen found in the atmosphere?
Ans: Oxygen is found in the atmosphere as ozone (O₂3) and molecular oxygen (O₃2).
Exercise: Questions and Answers
Q1. Why is the atmosphere necessary for living organisms?
Ans: The atmosphere is very essential for living organisms because it provides necessary gases such as oxygen, nitrogen, and carbon dioxide. It also helps in maintaining the average temperature of the Earth.
Q2. Why is water necessary for living organisms?
Ans: Water is extremely necessary for living organisms. Without water, life cannot exist. We use water for drinking, cooking, and maintaining cleanliness. Plants absorb water from the soil through their roots to prepare food. Moreover, water is required for metabolic activities in our body.
Q3. How do living organisms depend on soil? Are aquatic organisms completely independent of soil?
Ans: All living organisms depend on soil. Land animals live on soil, which is their primary habitat. All animals depend directly or indirectly on plants for food, and plants grow in soil. Thus, soil provides food to living organisms. Aquatic organisms are not directly dependent on soil. Rivers carry minerals from soil to seas, which are used by aquatic organisms. Therefore, they are indirectly dependent on soil.
Q4. You must have seen weather reports on television and in newspapers. How do you think weather forecasts are obtained?
Ans: Meteorologists predict weather based on temperature, wind speed, air pressure, etc. Artificial satellites help in collecting this information. These satellites send data to ground stations, from where it is broadcast through radio, television, and newspapers.
Q5. Human activities cause pollution of air, water, and soil. Do you think that identifying such activities in a particular area can reduce pollution?
Ans: Yes, identifying human activities can help reduce pollution levels. For example, reducing pollutants released from industries and factories can decrease pollution.
Q6. Write a note on how forests influence the quality of air, soil, and water.
Ans: Forests help in reducing pollution. Plants in forests bring changes in climate and their roots prevent soil erosion. Forests also help in increasing rainfall. Plants release oxygen, maintaining the balance of oxygen in the air. In this way, forests influence air, soil, and water quality.
Additional Questions & Answers
Q1. Define the following:
Biosphere, biotic components, abiotic components.
Ans:
Biosphere: The regions of land, water, and air where living organisms exist are collectively called the biosphere.
Biotic components: All living organisms in the biosphere are called biotic components.
Abiotic components: Non-living components such as air, water, and soil are called abiotic components.
Q2. Why is life not possible on Venus and Mars? What is the percentage of carbon dioxide on these planets?
Ans: Life is not possible on Venus and Mars because they lack oxygen and have a very high concentration of carbon dioxide. The percentage of carbon dioxide on these planets is about 95–97%.
Q3. Write two reasons for the increase in carbon dioxide.
Ans: (i) Cutting of trees increases carbon dioxide levels.
(ii) Burning of forests and fuels increases carbon dioxide significantly.
Q4. Write two methods to control carbon dioxide in the atmosphere.
Ans: (i) Green plants use carbon dioxide to produce glucose in the presence of sunlight.
(ii) Some marine organisms use dissolved carbonates to form their shells.
Q5. What is the range of temperature on the Moon?
Ans: The temperature on the Moon ranges from about -190°C to 110°C.
Q6. What is the water cycle?
Ans: The water cycle is the process in which water evaporates from different sources on Earth, goes into the atmosphere, and returns to the Earth as rain.
Q7. Briefly describe the nitrogen cycle.
Ans: Nitrogen is an essential element for living organisms. It is a component of proteins, nucleic acids, and some vitamins. Except for certain bacteria, most organisms cannot convert atmospheric nitrogen into usable forms. Some bacteria convert nitrogen into nitrates and nitrites. These bacteria are found in root nodules of leguminous plants and carry out nitrogen fixation. Plants absorb nitrates and nitrites and convert them into amino acids and proteins. Animals obtain proteins by eating plants. After the death of plants and animals, nitrogen compounds are converted back into nitrates and nitrites by bacteria. Thus, nitrogen circulates from the atmosphere to soil and water, thento living organisms, and back to the atmosphere.
Q8. What is the full form of CFC?
Ans: Chlorofluorocarbon.
Q9. Briefly describe the carbon cycle.
Ans: Carbon is found in nature in various forms. It exists in minerals as carbonates and hydrogen carbonates. In living organisms, carbon is a component of proteins, carbohydrates, fats, nucleic acids, and vitamins. The exoskeleton and endoskeleton of some organisms are made of calcium carbonate. Green plants use carbon dioxide and water in the process of photosynthesis to form glucose. During respiration, glucose breaks down and releases carbon dioxide into the atmosphere. Burning of fuels in industries and transport also releases carbon dioxide. Through various physical and biological processes, carbon circulates continuously in nature.
Multiple Choice Questions (MCQ)
Q1. Which component of the atmosphere is most essential for respiration in living organisms?
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) hydrogen
Ans: (b)
Q2. Which gas is mainly responsible for the greenhouse effect?
(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) helium
Ans: (c)
Q3. The ozone layer protects the Earth from:
(a) infrared rays
(b) visible light
(c) ultraviolet rays
(d) radio waves
Ans: (c)
Q4. Which of the following is a renewable resource?
(a) coal
(b) petroleum
(c) sunlight
(d) natural gas
Ans: (c)
Q5. Which process is responsible for cloud formation?
(a) evaporation
(b) condensation
(c) sublimation
(d) freezing
Ans: (b)
Q6. Wind is produced due to:
(a) rotation of Earth
(b) difference in air pressure
(c) gravity
(d) humidity
Ans: (b)
Q7. Which of the following causes air pollution?
(a) planting trees
(b) burning fossil fuels
(c) rainfall
(d) photosynthesis
Ans: (b)
Q8. Acid rain is caused by:
(a) oxygen and nitrogen
(b) carbon dioxide and hydrogen
(c) sulphur dioxide and nitrogen oxides
(d) helium and neon
Ans: (c)
Q9. Which of the following is a major source of water pollution?
(a) forests
(b) industries
(c) mountains
(d) wind
Ans: (b)
Q10. Soil is formed by:
(a) rainfall only
(b) weathering of rocks
(c) wind only
(d) sunlight only
Ans: (b)
Q11. Soil erosion is the:
(a) formation of soil
(b) removal of topsoil
(c) mixing of soil
(d) colouring of soil
Ans: (b)
Q12. Which of the following helps in preventing soil erosion?
(a) deforestation
(b) overgrazing
(c) planting trees
(d) mining
Ans: (c)
Q13. Water is essential for life because:
(a) it provides energy
(b) it helps in metabolism
(c) it produces oxygen
(d) it creates soil
Ans: (b)
Q14. Which of the following is a non-renewable resource?
(a) wind
(b) water
(c) coal
(d) sunlight
Ans: (c)
Q15. The water cycle includes:
(a) evaporation and condensation
(b) respiration and digestion
(c) digestion and excretion
(d) photosynthesis and respiration
Ans: (a)
Q16. Nitrogen is important for living organisms because it is a component of:
(a) carbohydrates
(b) proteins
(c) fats
(d) minerals
Ans: (b)
Q17. Which of the following bacteria fix nitrogen in soil?
(a) rhizobium
(b) lactobacillus
(c) streptococcus
(d) salmonella
Ans: (a)
Q18. Which layer of the Earth supports life?
(a) lithosphere
(b) atmosphere
(c) hydrosphere
(d) biosphere
Ans: (d)
Q19. Which gas is most abundant in the atmosphere?
(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) argon
Ans: (b)
Q20. Which of the following activities increases carbon dioxide in the atmosphere?
(a) planting trees
(b) deforestation
(c) rainfall
(d) evaporation
Ans: (b)
Q21. Which of the following is a fossil fuel?
(a) sunlight
(b) coal
(c) wind
(d) water
Ans: (b)
Q22. What is smog?
(a) mixture of smoke and fog
(b) mixture of air and water
(c) mixture of soil and water
(d) mixture of oxygen and nitrogen
Ans: (a)
Q23. Which of the following is an abiotic component?
(a) plants
(b) animals
(c) water
(d) bacteria
Ans: (c)
Q24. Which process do plants use to prepare food?
(a) respiration
(b) transpiration
(c) photosynthesis
(d) digestion
Ans: (c)
Q25. Which of the following is a cause of water pollution?
(a) clean water supply
(b) industrial waste
(c) rainfall
(d) filtration
Ans: (b)
Q26. Which natural resource is essential for breathing?
(a) water
(b) soil
(c) air
(d) minerals
Ans: (c)
Q27. Which of the following helps in maintaining oxygen balance in the atmosphere?
(a) animals
(b) vehicles
(c) plants
(d) industries
Ans: (c)
Q28. Which of the following is an example of a biotic component?
(a) air
(b) soil
(c) plant
(d) water
Ans: (c)
Q29. The main cause of global warming is:
(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) hydrogen
Ans: (c)
Q30. Which of the following conserves natural resources?
(a) deforestation
(b) overuse
(c) recycling
(d) pollution
Ans: (c)
