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Natural Resources – CBSE NCERT Study Resources

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Natural Resources

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9th

9th - Science

Natural Resources

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Overview

Natural resources are materials or substances occurring in nature that can be exploited for economic gain or used to support life. This chapter explores various types of natural resources, their importance, and the need for their conservation.

Types of Natural Resources

Natural resources can be broadly classified into two categories:

  • Renewable Resources: These are resources that can be replenished naturally over time, such as sunlight, wind, water, and forests.
  • Non-Renewable Resources: These are resources that cannot be easily replenished once depleted, such as fossil fuels (coal, petroleum) and minerals.

Air (Atmosphere)

The atmosphere is a blanket of gases surrounding the Earth, essential for sustaining life. It consists of nitrogen (78%), oxygen (21%), and traces of other gases like carbon dioxide and argon.

Key roles of the atmosphere include:

  • Providing oxygen for respiration.
  • Protecting Earth from harmful UV radiation via the ozone layer.
  • Regulating temperature through the greenhouse effect.

Water (Hydrosphere)

Water covers about 71% of the Earth's surface and exists in three forms: solid (ice), liquid (water), and gas (water vapor).

The water cycle describes the continuous movement of water on, above, and below the Earth's surface through processes like evaporation, condensation, and precipitation.

Importance of water:

  • Essential for all living organisms.
  • Supports agriculture and industries.
  • Maintains ecological balance.

Soil (Lithosphere)

Soil is the uppermost layer of the Earth's crust, formed by the weathering of rocks and decomposition of organic matter. It is a vital resource for agriculture and ecosystems.

Factors affecting soil formation:

  • Climate
  • Parent rock material
  • Topography
  • Biological activity

Biosphere

The biosphere is the global ecological system integrating all living organisms and their interactions with the Earth's resources (air, water, soil).

Biodiversity refers to the variety of life forms (plants, animals, microorganisms) in a given ecosystem, contributing to ecological stability.

Conservation of Natural Resources

Sustainable practices to conserve natural resources include:

  • Reducing, reusing, and recycling materials.
  • Using alternative energy sources (solar, wind).
  • Afforestation and preventing deforestation.
  • Rainwater harvesting and efficient water management.

All Question Types with Solutions – CBSE Exam Pattern

Explore a complete set of CBSE-style questions with detailed solutions, categorized by marks and question types. Ideal for exam preparation, revision and practice.

Very Short Answer (1 Mark) – with Solutions (CBSE Pattern)

These are 1-mark questions requiring direct, concise answers. Ideal for quick recall and concept clarity.

Question 1:
What is the main source of freshwater on Earth?
Answer:

Groundwater and surface water.

Question 2:
Name one greenhouse gas responsible for global warming.
Answer:

Carbon dioxide (CO2).

Question 3:
What is the process of water cycle where water turns into vapor?
Answer:

Evaporation.

Question 4:
Which gas is most abundant in the Earth's atmosphere?
Answer:

Nitrogen (N2).

Question 5:
What is the primary cause of soil erosion?
Answer:

Deforestation and overgrazing.

Question 6:
Name one renewable energy source.
Answer:

Solar energy.

Question 7:
What is the role of nitrogen-fixing bacteria in soil?
Answer:

Convert atmospheric nitrogen into nitrates.

Question 8:
Which layer of the atmosphere contains the ozone layer?
Answer:

Stratosphere.

Question 9:
What is the main component of biogas?
Answer:

Methane (CH4).

Question 10:
Name one fossil fuel.
Answer:

Coal.

Question 11:
What is the process by which plants release water vapor?
Answer:

Transpiration.

Question 12:
Which gas is essential for photosynthesis?
Answer:

Carbon dioxide (CO2).

Question 13:
What is the major cause of air pollution in cities?
Answer:

Vehicle emissions.

Question 14:
Name one method to conserve water resources.
Answer:

Rainwater harvesting.

Question 15:
What is the primary source of energy for the water cycle?
Answer:

The Sun is the primary source of energy for the water cycle. It provides the heat required for evaporation of water from water bodies.

Question 16:
Name two greenhouse gases.
Answer:

Two greenhouse gases are carbon dioxide (CO₂) and methane (CH₄). These gases trap heat in the Earth's atmosphere, contributing to global warming.

Question 17:
Define soil erosion.
Answer:

Soil erosion is the process where the top layer of fertile soil is removed by natural forces like wind, water, or human activities such as deforestation.

Question 18:
What is the role of nitrogen-fixing bacteria in the nitrogen cycle?
Answer:

Nitrogen-fixing bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), making it usable for plants. This process enriches the soil with essential nutrients.

Question 19:
Why is the ozone layer important for life on Earth?
Answer:

The ozone layer absorbs harmful ultraviolet (UV) radiation from the Sun, protecting living organisms from skin cancer, eye damage, and other health issues.

Question 20:
List two methods to conserve water at home.
Answer:
  • Using a bucket instead of a shower for bathing.
  • Fixing leaky taps to prevent water wastage.
Question 21:
What is the main cause of acid rain?
Answer:

Acid rain is caused by the release of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the atmosphere from burning fossil fuels, which react with water vapor to form acids.

Question 22:
How does afforestation help in maintaining the balance of oxygen and carbon dioxide?
Answer:

Afforestation increases the number of trees, which absorb carbon dioxide (CO₂) during photosynthesis and release oxygen (O₂), thus maintaining the balance.

Question 23:
Name one natural and one human-made source of air pollution.
Answer:
  • Natural source: Volcanic eruptions releasing ash and gases.
  • Human-made source: Vehicles emitting exhaust fumes.
Question 24:
What is the significance of the three R's in waste management?
Answer:

The three R's—Reduce, Reuse, Recycle—help minimize waste generation, conserve resources, and reduce environmental pollution by promoting sustainable practices.

Question 25:
Why is the conservation of fossil fuels important?
Answer:

Conserving fossil fuels like coal and petroleum is crucial because they are non-renewable resources. Overuse leads to depletion and increases pollution, affecting the environment.

Question 26:
How does the presence of algae in water bodies indicate pollution?
Answer:

Excessive growth of algae (algal bloom) indicates eutrophication, caused by high levels of nutrients like phosphates and nitrates from sewage or fertilizers, leading to oxygen depletion in water.

Very Short Answer (2 Marks) – with Solutions (CBSE Pattern)

These 2-mark questions test key concepts in a brief format. Answers are expected to be accurate and slightly descriptive.

Question 1:
Define natural resources and give two examples.
Answer:

Natural resources are materials or substances occurring in nature that can be exploited for economic gain or human use.
Examples: Forests (provide timber, oxygen) and Water (essential for life, agriculture).

Question 2:
Why is the atmosphere considered a vital natural resource?
Answer:

The atmosphere is crucial because:

  • It contains oxygen for respiration.
  • Acts as a shield against harmful UV rays.
  • Regulates Earth's temperature via the greenhouse effect.

Question 3:
Name two human activities that lead to the depletion of water resources.
Answer:

  • Over-extraction of groundwater for agriculture.
  • Industrial pollution contaminating freshwater sources.

Question 4:
How does afforestation help in conserving natural resources?
Answer:

Afforestation helps by:

  • Preventing soil erosion through root systems.
  • Enhancing groundwater recharge.
  • Absorbing carbon dioxide, reducing global warming.

Question 5:
What is the role of ozone layer in the atmosphere?
Answer:

The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun, protecting living organisms from skin cancer and other health risks.

Question 6:
Differentiate between renewable and non-renewable resources with examples.
Answer:

  • Renewable: Replenished naturally (e.g., solar energy, wind energy).
  • Non-renewable: Finite and deplete over time (e.g., coal, petroleum).

Question 7:
Explain how soil erosion affects agricultural productivity.
Answer:

Soil erosion removes the nutrient-rich topsoil, reducing fertility and water retention capacity, which lowers crop yields and disrupts ecosystems.

Question 8:
Why is water conservation essential? Suggest one method to conserve water.
Answer:

Water conservation ensures sustainable availability for future generations.
Method: Rainwater harvesting to recharge groundwater and reduce runoff.

Question 9:
What are fossil fuels? Why are they classified as non-renewable?
Answer:

Fossil fuels (e.g., coal, oil) are formed from ancient organic matter over millions of years. They are non-renewable because their formation rate is much slower than their consumption.

Question 10:
How does deforestation contribute to climate change?
Answer:

Deforestation increases carbon dioxide levels in the atmosphere as trees (which absorb CO2) are removed, intensifying the greenhouse effect and global warming.

Question 11:
List two measures to reduce air pollution caused by vehicles.
Answer:

  • Using CNG (cleaner fuel) instead of petrol/diesel.
  • Promoting public transport to reduce vehicle emissions.

Short Answer (3 Marks) – with Solutions (CBSE Pattern)

These 3-mark questions require brief explanations and help assess understanding and application of concepts.

Question 1:
Explain the role of forests in maintaining the ecological balance.
Answer:

Forests play a crucial role in maintaining ecological balance by:

  • Producing oxygen through photosynthesis, which is essential for all living organisms.
  • Absorbing carbon dioxide, thus reducing the greenhouse effect and combating climate change.
  • Providing habitat to numerous species, thereby preserving biodiversity.
  • Preventing soil erosion by holding the soil with their roots and maintaining the water cycle.
Additionally, forests act as natural water filters and help in replenishing groundwater.

Question 2:
Describe how water is considered a renewable resource.
Answer:

Water is considered a renewable resource because of the water cycle, which continuously replenishes it.

  • Evaporation turns water into vapor, forming clouds.
  • Condensation leads to precipitation (rain, snow), returning water to Earth.
  • This cycle ensures a constant supply, making water renewable.
However, overuse or pollution can make it scarce, so sustainable management is essential.

Question 3:
What are the harmful effects of excessive use of fertilizers on soil fertility?
Answer:

Excessive use of fertilizers harms soil fertility by:

  • Reducing microbial activity, which is vital for nutrient recycling.
  • Causing soil acidification or alkalinity, making it unfit for plant growth.
  • Leading to water pollution when fertilizers seep into groundwater or runoff into rivers.
  • Decreasing soil's organic content over time, making it less fertile.
Sustainable farming practices like crop rotation can help mitigate these effects.

Question 4:
How does deforestation contribute to global warming?
Answer:

Deforestation contributes to global warming in the following ways:

  • Trees absorb carbon dioxide; cutting them down increases its concentration in the atmosphere.
  • Burning forests releases stored carbon, further raising greenhouse gas levels.
  • Reduced tree cover disrupts the water cycle, leading to drier climates and higher temperatures.
Protecting forests is critical to combating climate change.

Question 5:
Explain the importance of conserving fossil fuels for future generations.
Answer:

Conserving fossil fuels is vital because:

  • They are non-renewable and will deplete if overused.
  • Burning them releases greenhouse gases, worsening air pollution and climate change.
  • Future generations will need them for essential purposes like transportation and energy.
Switching to renewable energy sources like solar or wind power can help preserve fossil fuels.

Question 6:
Describe the process of rainwater harvesting and its benefits.
Answer:

Rainwater harvesting involves collecting and storing rainwater for later use. The process includes:

  • Collecting rainwater from rooftops or open areas.
  • Filtering it to remove debris.
  • Storing it in tanks or recharging groundwater.
Benefits include:
  • Reducing dependence on groundwater.
  • Preventing water scarcity during droughts.
  • Lowering water bills and conserving resources.
It is a sustainable way to manage water.

Question 7:
What are the renewable and non-renewable resources? Give two examples of each.
Answer:

Renewable resources are those that can be replenished naturally over time, such as:

  • Solar energy – harnessed from sunlight.
  • Wind energy – generated from wind turbines.
Non-renewable resources are finite and take millions of years to form, such as:
  • Coal – a fossil fuel used for energy.
  • Petroleum – used for fuel and manufacturing products.
Sustainable use of renewable resources is essential for future generations.

Question 8:
Describe how water is considered a natural resource and its importance.
Answer:

Water is a vital natural resource because:

  • It is essential for all forms of life, including humans, animals, and plants.
  • It supports agriculture, industries, and daily activities like drinking and sanitation.
  • It helps in regulating the Earth's temperature and climate.
  • It is a habitat for aquatic organisms, maintaining biodiversity.
However, due to pollution and overuse, conserving water is critical for sustainability.

Question 9:
What is soil erosion? Mention two human activities that contribute to it.
Answer:

Soil erosion is the process where the top layer of soil is worn away due to natural forces like wind and water or human activities. Two human activities that contribute to soil erosion are:

  • Deforestation – Cutting down trees removes the roots that hold soil together.
  • Overgrazing – Excessive grazing by livestock removes vegetation cover, exposing soil to erosion.
Preventing these activities can help conserve soil fertility.

Question 10:
Explain the importance of the atmosphere as a natural resource.
Answer:

The atmosphere is crucial because:

  • It provides oxygen for respiration in living organisms.
  • It acts as a protective shield against harmful UV radiation from the sun.
  • It regulates Earth's temperature through the greenhouse effect.
  • It enables weather patterns and the water cycle, essential for life.
Pollution and climate change threaten the atmosphere, making its conservation vital.

Question 11:
How does mineral wealth contribute to a country's development?
Answer:

Mineral wealth contributes to a country's development by:

  • Providing raw materials for industries, such as iron for steel production.
  • Generating employment opportunities in mining and related sectors.
  • Boosting economic growth through exports and revenue generation.
  • Supporting infrastructure development, such as roads and buildings.
However, sustainable mining practices are necessary to prevent environmental degradation.

Long Answer (5 Marks) – with Solutions (CBSE Pattern)

These 5-mark questions are descriptive and require detailed, structured answers with proper explanation and examples.

Question 1:
Explain the water cycle and its importance in maintaining natural resources.
Answer:
Concept Overview

The water cycle is the continuous movement of water between the Earth's surface and atmosphere through evaporation, condensation, and precipitation.

Process Explanation
  • Evaporation: Water turns into vapor due to heat.
  • Condensation: Vapor cools to form clouds.
  • Precipitation: Water falls as rain or snow.
Real-world Application

Our textbook shows how forests help in maintaining the cycle. In cities, excessive concrete reduces groundwater recharge, affecting water availability.

Question 2:
Describe how soil erosion occurs and suggest methods to prevent it.
Answer:
Concept Overview

Soil erosion is the removal of topsoil by wind or water, degrading land quality.

Process Explanation
  • Water erosion: Heavy rain washes away soil.
  • Wind erosion: Strong winds blow loose soil.
Real-world Application

Our textbook mentions terrace farming in hilly areas. Planting trees like neem reduces erosion by holding soil together.

Question 3:
Explain the role of forests in conserving biodiversity and maintaining ecological balance.
Answer:
Concept Overview

Forests provide habitats for diverse species, ensuring biodiversity and ecological stability.

Process Explanation
  • Forests act as carbon sinks, reducing global warming.
  • They prevent soil erosion and regulate water cycles.
Real-world Application

Our textbook highlights the Amazon rainforest. In India, the Sundarbans protect endangered species like the Bengal tiger.

Question 4:
Discuss the causes and effects of air pollution with examples.
Answer:
Concept Overview

Air pollution occurs when harmful substances like smoke and chemicals enter the atmosphere.

Process Explanation
  • Vehicles emit CO2, causing smog.
  • Factories release sulfur dioxide, leading to acid rain.
Real-world Application

Our textbook shows Delhi's air quality issues. Using CNG in buses reduces pollution, as seen in cities like Mumbai.

Question 5:
How does the greenhouse effect contribute to global warming? Provide NCERT and real-life examples.
Answer:
Concept Overview

The greenhouse effect traps heat in the atmosphere, raising Earth's temperature.

Process Explanation
  • Gases like CO2 absorb infrared radiation.
  • Human activities increase these gases.
Real-world Application

Our textbook mentions melting glaciers. In real life, rising sea levels threaten coastal cities like Chennai.

Question 6:
Describe how biogeochemical cycles like the nitrogen cycle sustain life.
Answer:
Concept Overview

The nitrogen cycle converts atmospheric nitrogen into usable forms for plants and animals.


Process Explanation
  • Nitrogen fixation by bacteria.
  • Absorption by plants.
  • Return to soil via decomposition.

Real-world Application

NCERT explains how legumes enrich soil. Farmers use crop rotation to maintain nitrogen levels naturally.

Question 7:
How does soil erosion impact natural resources, and what are preventive measures?
Answer:
Concept Overview

Soil erosion removes fertile topsoil, reducing land productivity.


Process Explanation
  • Caused by deforestation or overgrazing.
  • Leads to loss of nutrients.

Real-world Application

Our textbook mentions terrace farming in hills. Planting trees like Prosopis prevents erosion in dry areas.

Question 8:
Explain the role of forests in conserving biodiversity and water resources.
Answer:
Concept Overview

Forests act as habitats and regulate water cycles.


Process Explanation
  • They prevent soil erosion.
  • Maintain groundwater levels.

Real-world Application

NCERT highlights the Amazon rainforest. In India, the Chipko movement saved trees and water sources.

Question 9:
What are fossil fuels, and why is their overuse harmful to natural resources?
Answer:
Concept Overview

Fossil fuels like coal and oil are non-renewable energy sources.


Process Explanation
  • Formed over millions of years.
  • Burning releases pollutants.

Real-world Application

Our textbook links them to air pollution. Solar energy, like in Rajasthan, is a cleaner alternative.

Question 10:
What is biogeochemical cycling? Explain the carbon cycle with examples.
Answer:
Concept Overview

Biogeochemical cycles recycle nutrients like carbon between living organisms and the environment.


Process Explanation

The carbon cycle involves photosynthesis (plants absorb CO2) and respiration (animals release it). NCERT shows how fossil fuels store carbon.


Real-world Application

Burning fossil fuels increases CO2, causing global warming. Forests act as carbon sinks.


[Diagram: Carbon cycle with arrows]
Question 11:
How do forests help in conserving water resources? Provide NCERT-based evidence.
Answer:
Concept Overview

Forests maintain water balance by reducing runoff and recharging groundwater.


Process Explanation

Our textbook states tree roots hold soil, allowing water to percolate. NCERT cites the Himalayan forests preventing floods.


Real-world Application

In cities like Chennai, deforestation led to water scarcity. Afforestation projects revive water tables.


[Diagram: Forest intercepting rainfall]
Question 12:
Discuss the role of wind energy as a sustainable natural resource.
Answer:
Concept Overview

Wind energy is renewable and harnessed using turbines to generate electricity.


Process Explanation

NCERT explains how wind rotates turbine blades, converting kinetic energy to electrical energy without pollution.


Real-world Application

India’s Tamil Nadu has large wind farms. It reduces reliance on coal, cutting greenhouse gases.


[Diagram: Wind turbine with energy flow]
Question 13:
Explain the importance of water as a natural resource and discuss the causes and effects of water pollution. Suggest two measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It is crucial for survival, agriculture, industries, and maintaining ecological balance. Water supports photosynthesis in plants, regulates body temperature in animals, and is used in households for drinking, cleaning, and sanitation.

Causes of water pollution:

  • Industrial waste discharge containing toxic chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste dumping.
Effects of water pollution:
  • Harm to aquatic life due to reduced oxygen levels.
  • Spread of waterborne diseases like cholera.
  • Contamination of groundwater, making it unfit for consumption.
Measures to conserve water:
1. Rainwater harvesting: Collecting and storing rainwater for future use.
2. Wastewater treatment: Reusing treated water for irrigation and industrial purposes.

Question 14:
Describe the carbon cycle in nature with a labeled diagram. How do human activities disrupt this cycle, and what are its consequences?
Answer:

The carbon cycle is a biogeochemical process where carbon is exchanged among the atmosphere, oceans, soil, and living organisms. Key steps:
1. Photosynthesis: Plants absorb CO2 from the air and convert it into glucose.
2. Respiration: Living organisms release CO2 back into the atmosphere.
3. Decomposition: Dead organisms are broken down, releasing carbon into the soil.
4. Combustion: Burning fossil fuels releases stored carbon as CO2.

Human disruptions:

  • Excessive burning of fossil fuels increases atmospheric CO2.
  • Deforestation reduces the number of trees absorbing CO2.
Consequences:
  • Global warming due to the greenhouse effect.
  • Ocean acidification harming marine life.
Diagram: (A labeled diagram showing the flow of carbon between the atmosphere, plants, animals, and fossil fuels.)

Question 15:
Explain the importance of water as a natural resource and discuss the major causes of its depletion. Suggest any three measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. However, due to human activities, water resources are depleting rapidly.

Causes of water depletion:
1. Overuse in agriculture: Excessive irrigation and inefficient water management lead to groundwater depletion.
2. Industrial waste: Pollution from industries contaminates freshwater sources.
3. Deforestation: Reduces groundwater recharge by affecting the water cycle.
4. Urbanization: Increases demand and reduces natural water bodies.

Measures to conserve water:

  • Adopting rainwater harvesting to recharge groundwater.
  • Using drip irrigation in agriculture to minimize water wastage.
  • Reducing industrial pollution by treating wastewater before disposal.

Conserving water ensures sustainability for future generations and maintains ecological balance.

Question 16:
Explain the importance of water as a natural resource and discuss the major causes and consequences of water pollution. Suggest any three measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. Without water, life on Earth would not be possible.

The major causes of water pollution include:

  • Industrial waste discharge containing harmful chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste dumping into water bodies.

The consequences of water pollution are severe:

  • Contaminated water leads to waterborne diseases like cholera and dysentery.
  • It harms aquatic life, disrupting ecosystems.
  • Polluted water reduces the availability of clean drinking water.

Three measures to conserve water are:

  • Implementing rainwater harvesting to recharge groundwater.
  • Reducing water wastage by fixing leaks and using water-efficient appliances.
  • Promoting awareness about water conservation through community programs.

By adopting these practices, we can ensure sustainable use of water for future generations.

Question 17:
Explain the importance of water as a natural resource and discuss the major causes of water pollution. Suggest any three measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance.

Importance of Water:

  • It is vital for photosynthesis in plants, which produces oxygen and food.
  • It helps regulate Earth's temperature through the water cycle.
  • It is used for drinking, irrigation, and industrial purposes.
  • It supports aquatic ecosystems, providing habitat for marine life.

Major Causes of Water Pollution:
  • Industrial waste discharge containing harmful chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste dumping into water bodies.
  • Oil spills from ships and tankers.

Measures to Conserve Water:
  • Adopting rainwater harvesting to recharge groundwater.
  • Reducing water wastage by fixing leaks and using efficient irrigation methods like drip irrigation.
  • Promoting awareness about water conservation and recycling wastewater.

Question 18:
Explain the importance of water as a natural resource and discuss the major causes and consequences of water pollution. Suggest any three measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. Without water, life on Earth would not be possible.

The major causes of water pollution include:

  • Industrial waste discharge containing harmful chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste dumping into water bodies.

The consequences of water pollution are severe:

  • Contaminated water leads to waterborne diseases like cholera and dysentery.
  • It harms aquatic life, disrupting ecosystems.
  • Polluted water reduces the availability of clean drinking water.

Three measures to conserve water are:

  • Practicing rainwater harvesting to recharge groundwater.
  • Fixing leaky taps and using water-efficient appliances.
  • Promoting awareness about water conservation in communities.

By adopting these measures, we can ensure sustainable use of water for future generations.

Question 19:
Explain the importance of water as a natural resource and discuss the causes and consequences of water pollution. Suggest two measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. Without water, life on Earth would not be possible.

The causes of water pollution include:

  • Industrial waste discharge containing harmful chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste dumping into water bodies.

The consequences of water pollution are severe:

  • Contaminated water leads to waterborne diseases like cholera and dysentery.
  • It harms aquatic life, disrupting ecosystems.
  • Polluted water reduces the availability of clean drinking water.

Two measures to conserve water are:

  • Rainwater harvesting: Collecting and storing rainwater for future use.
  • Reducing water wastage: Fixing leaks, using water-efficient appliances, and practicing mindful usage.

By adopting these measures, we can ensure sustainable water management and protect this vital resource for future generations.

Question 20:
Explain the importance of water as a natural resource. Discuss how human activities are affecting its availability and suggest measures to conserve it.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. Without water, life on Earth would not be possible.

Human activities such as deforestation, pollution, and over-extraction of groundwater are severely affecting water availability. Industrial waste, sewage, and agricultural runoff contaminate water bodies, making them unfit for use. Excessive use of water in urban areas and inefficient irrigation methods in agriculture further deplete freshwater resources.

To conserve water, the following measures can be adopted:

  • Implementing rainwater harvesting to recharge groundwater levels.
  • Reducing water wastage by fixing leaks and using water-efficient appliances.
  • Promoting drip irrigation in agriculture to minimize water loss.
  • Treating and reusing wastewater for non-potable purposes.
  • Creating awareness about water conservation through community programs.

By adopting these practices, we can ensure sustainable water management for future generations.

Question 21:
Explain the importance of water as a natural resource and discuss the major causes and consequences of water pollution. Suggest any two measures to conserve water.
Answer:

Water is one of the most essential natural resources for all living organisms. It plays a crucial role in various biological processes, agriculture, industries, and maintaining ecological balance. Without water, life on Earth would not be possible.

The major causes of water pollution include:

  • Industrial waste discharge containing harmful chemicals.
  • Agricultural runoff with pesticides and fertilizers.
  • Domestic sewage and plastic waste.

The consequences of water pollution are severe:

  • It harms aquatic life and disrupts ecosystems.
  • Contaminated water causes diseases like cholera and dysentery in humans.
  • It reduces the availability of clean drinking water.

Two measures to conserve water are:

  • Rainwater harvesting to recharge groundwater.
  • Reducing water wastage by fixing leaks and using water-efficient appliances.

Question 22:
Describe the role of forests in maintaining the ecological balance. Explain how deforestation affects the environment and suggest two sustainable practices to protect forests.
Answer:

Forests play a vital role in maintaining the ecological balance by:

  • Producing oxygen through photosynthesis and absorbing carbon dioxide.
  • Providing habitat for diverse flora and fauna.
  • Preventing soil erosion and regulating the water cycle.

Deforestation has harmful effects on the environment:

  • It leads to loss of biodiversity and extinction of species.
  • Increases carbon dioxide levels, contributing to global warming.
  • Causes soil degradation and disrupts rainfall patterns.

Two sustainable practices to protect forests are:

  • Promoting afforestation and reforestation programs.
  • Encouraging the use of recycled paper and reducing wood consumption.

Case-based Questions (4 Marks) – with Solutions (CBSE Pattern)

These 4-mark case-based questions assess analytical skills through real-life scenarios. Answers must be based on the case study provided.

Question 1:
A village faces water scarcity due to erratic rainfall. Farmers rely on groundwater, causing depletion. Analyze the situation using NCERT examples and suggest solutions.
Answer:
Case Summary

Groundwater overuse leads to scarcity, as studied in NCERT's 'Natural Resources'.

Scientific Principle
  • Water cycle balances renewable resources.
  • Over-extraction disrupts aquifer recharge.
Solution Approach
  • Adopt rainwater harvesting (NCERT example: Rajasthan's khadins).
  • Use drip irrigation to reduce wastage.
Question 2:
A factory emits CO₂ and SO₂, causing acid rain. Explain its impact on soil fertility with NCERT references.
Answer:
Case Summary

Acid rain lowers soil pH, harming crops, as in NCERT's 'Air Pollution'.

Scientific Principle
  • Acid rain leaches nutrients like calcium.
  • Increases aluminum toxicity.
Solution Approach
  • Add limestone to neutralize acidity (NCERT example).
  • Install scrubbers in factories.
Question 3:
A forest area shows reduced biodiversity due to deforestation. Link this to carbon cycle disruption using NCERT concepts.
Answer:
Case Summary

Forests maintain carbon balance, as in NCERT's 'Carbon Cycle'.

Scientific Principle
  • Trees absorb CO₂ via photosynthesis.
  • Deforestation raises atmospheric greenhouse gases.
Solution Approach
  • Promote afforestation (NCERT's Chipko Movement).
  • Use alternative fuels to reduce logging.
Question 4:
A coastal town faces soil erosion due to tidal waves. Propose natural and man-made solutions with NCERT examples.
Answer:
Case Summary

Erosion removes fertile topsoil, studied in NCERT's 'Soil Resources'.

Scientific Principle
  • Mangroves reduce wave impact (NCERT example: Sundarbans).
  • Gabions trap sediments.
Solution Approach
  • Plant mangroves as natural barriers.
  • Build sea walls for protection.
Question 5:
A factory emits CO2 and SO2, causing acid rain. Explain the process and its impact on monuments like the Taj Mahal.
Answer:
Case Summary

Factory gases dissolve in rain, forming acids. Our textbook mentions Taj Mahal’s discoloration.

Scientific Principle
  • SO2 forms sulfuric acid.
  • Marble (CaCO3) corrodes.
Solution Approach
  • Use scrubbers (NCERT example).
  • Shift to CNG like Delhi’s buses.
Question 6:
A forest has declining biodiversity due to deforestation. Link this to the NCERT example of the Amazon and propose conservation methods.
Answer:
Case Summary

Forest loss reduces species. NCERT cites Amazon’s shrinking habitat.

Scientific Principle
  • Trees maintain ecological balance.
  • Loss disrupts food chains.
Solution Approach
  • Afforestation (NCERT’s Chipko Movement).
  • Protected areas like Sundarbans.
Question 7:
Farmers burn crop residue, worsening air pollution. Compare this to Delhi’s smog and suggest alternatives.
Answer:
Case Summary

Burning residue releases smoke. NCERT links it to Delhi’s winter smog.

Scientific Principle
  • Combustion produces particulate matter.
  • Health hazards arise.
Solution Approach
  • Use residue for compost (NCERT example).
  • Adopt happy seeders like Punjab.
Question 8:
A village faces water scarcity due to erratic rainfall. Farmers rely on groundwater, causing depletion. Analyze the situation using NCERT examples and suggest solutions.
Answer:
Case Summary

Groundwater overuse leads to scarcity, as seen in Rajasthan (NCERT).

Scientific Principle
  • Water cycle disruption from excessive extraction.
  • Soil moisture loss affects agriculture.
Solution Approach
  • Rainwater harvesting (NCERT example: Tamil Nadu’s tanks).
  • Crop rotation to reduce water demand.
Question 9:
A factory emits CO₂ and particulate matter, harming local air quality. Relate this to NCERT’s air pollution concepts and propose mitigation steps.
Answer:
Case Summary

Industrial emissions mimic Delhi’s air pollution (NCERT).

Scientific Principle
  • CO₂ increases greenhouse effect.
  • Particulates cause respiratory diseases.
Solution Approach
  • Install electrostatic precipitators (NCERT example).
  • Shift to solar energy like Gujarat’s solar parks.
Question 10:
Deforestation near a river causes soil erosion and loss of biodiversity. Explain using NCERT’s biogeochemical cycles and conservation methods.
Answer:
Case Summary

Forest loss disrupts cycles, as in Amazon (NCERT reference).

Scientific Principle
  • Nitrogen cycle breaks without trees.
  • Habitat destruction reduces species.
Solution Approach
  • Afforestation (NCERT: Chipko Movement).
  • Terrace farming to prevent erosion.
Question 11:
A coastal area faces oil spills, threatening marine life. Apply NCERT’s natural resource concepts to address the issue.
Answer:
Case Summary

Oil spills harm ecosystems, like Mumbai’s 2010 spill (NCERT).

Scientific Principle
  • Oil blocks sunlight, reducing phytoplankton.
  • Food chain disruption occurs.
Solution Approach
  • Use skimmers (NCERT: containment methods).
  • Promote biodegradable cleaners.
Question 12:

In a village, farmers noticed that the soil in their fields was becoming less fertile over time. They also observed that the nearby river water had become muddy due to soil erosion. Based on this case:

  • Identify two natural resources being affected here.
  • Suggest two sustainable practices the farmers can adopt to improve soil fertility and prevent erosion.
Answer:

The two natural resources affected are soil (due to loss of fertility) and water (due to sedimentation from erosion).

Two sustainable practices to improve fertility and prevent erosion:

  • Crop Rotation: Growing different crops in succession helps replenish soil nutrients naturally.
    Example: Legumes fix nitrogen, improving soil health.
  • Contour Plowing: Plowing along the natural contours of the land reduces water runoff and soil loss.
    Additional benefit: Terraces or cover crops can further stabilize the soil.
Question 13:

A group of students conducted an experiment to compare the water-holding capacity of sandy, clayey, and loamy soil. They observed that loamy soil retained the most water while sandy soil drained quickly. Analyze their findings and answer:

  • Why does loamy soil have better water retention than sandy soil?
  • How does this property make loamy soil ideal for agriculture?
Answer:

Loamy soil retains more water than sandy soil because:

  • It has a balanced mixture of sand, silt, and clay, creating smaller pores that hold water effectively.
    Sandy soil has large particles with gaps, causing rapid drainage.

Loamy soil is ideal for agriculture because:

  • Its water-holding capacity ensures plants receive moisture for longer periods.
    Additional benefit: It also provides good aeration and nutrient retention, supporting healthy root growth.
Question 14:
A group of students conducted an experiment to study the effect of deforestation on soil erosion. They observed that areas with dense vegetation had less soil erosion compared to areas with little or no vegetation. Based on their observations, answer the following:
(a) Explain the role of vegetation in preventing soil erosion.
(b) Suggest two measures to reduce soil erosion in deforested areas.
Answer:

(a) Vegetation plays a crucial role in preventing soil erosion by:

  • Binding the soil with their roots, which holds the soil particles together and prevents them from being washed away by water or blown away by wind.
  • Reducing the impact of raindrops on the soil surface, which minimizes the displacement of soil particles.
  • Slowing down the flow of water, allowing it to percolate into the ground rather than carrying away the topsoil.

(b) Two measures to reduce soil erosion in deforested areas are:

  • Afforestation: Planting trees and plants to restore vegetation cover, which will stabilize the soil.
  • Terracing: Creating steps or terraces on slopes to reduce the speed of water flow and prevent soil loss.

Question 15:
A farmer noticed that the yield from his crops was decreasing over the years despite using chemical fertilizers. Upon consulting an agricultural expert, he learned about the importance of sustainable farming practices. Answer the following:
(a) Why do excessive chemical fertilizers reduce soil fertility in the long run?
(b) Name two natural methods to replenish soil nutrients and explain how they work.
Answer:

(a) Excessive use of chemical fertilizers reduces soil fertility over time because:

  • They alter the pH balance of the soil, making it either too acidic or too alkaline, which affects microbial activity.
  • They lead to the depletion of organic matter, reducing the soil's ability to retain water and nutrients.
  • They cause the accumulation of harmful salts, which can damage the soil structure and hinder plant growth.

(b) Two natural methods to replenish soil nutrients are:

  • Crop Rotation: Growing different crops in succession on the same land helps maintain soil fertility by balancing nutrient usage and preventing pest buildup.
  • Organic Manure: Adding decomposed plant or animal waste enriches the soil with essential nutrients and improves its texture and water-holding capacity.

Question 16:
A village near a forest is experiencing frequent droughts and declining groundwater levels. Farmers report reduced crop yields due to erratic rainfall. Analyze the situation and suggest sustainable practices the villagers can adopt to conserve water and improve agricultural productivity.
Answer:

The situation indicates over-exploitation of natural resources like water and deforestation, leading to ecological imbalance. Here are sustainable practices:

  • Rainwater Harvesting: Build check dams and percolation pits to recharge groundwater.
  • Afforestation: Plant native trees to improve rainfall patterns and prevent soil erosion.
  • Drip Irrigation: Use efficient watering techniques to minimize water wastage.
  • Crop Rotation: Grow legumes to restore soil nitrogen and maintain fertility.

These methods align with sustainable development by balancing resource use and conservation.

Question 17:
A factory near a river discharges untreated waste, causing water pollution. Aquatic life is dying, and locals face health issues. Identify the pollutants and propose measures to restore the river's health while ensuring industrial growth.
Answer:

The pollutants likely include toxic chemicals, heavy metals, and organic waste. Restoration measures:

  • Effluent Treatment Plants (ETPs): Factories must install ETPs to treat waste before discharge.
  • Bioremediation: Use microorganisms to break down pollutants naturally.
  • Public Awareness: Educate locals about pollution's impact and encourage reporting violations.
  • Government Regulations: Enforce strict penalties for non-compliance with environmental laws.

This approach ensures industrial growth without compromising ecosystem health.

Question 18:
A group of students conducted an experiment to study the effect of deforestation on soil erosion. They observed that soil erosion increased significantly in areas where trees were cut down. Based on their findings, answer the following:
(i) Explain the role of trees in preventing soil erosion.
(ii) Suggest two sustainable practices to reduce soil erosion in deforested areas.
Answer:

(i) Trees play a crucial role in preventing soil erosion by:
1. Root Binding: The roots of trees hold the soil particles together, preventing them from being washed away by water or blown away by wind.
2. Canopy Protection: The leaves and branches of trees reduce the impact of rainfall on the soil, minimizing the displacement of soil particles.
3. Water Absorption: Trees absorb excess water, reducing surface runoff that carries away topsoil.

(ii) Two sustainable practices to reduce soil erosion in deforested areas are:
1. Afforestation: Planting new trees to restore the forest cover and stabilize the soil.
2. Terrace Farming: Creating stepped fields on slopes to slow down water flow and reduce soil loss. Additionally, using cover crops like grasses can protect the soil between harvests.

Question 19:
A village near a river faces frequent floods during the monsoon season. The villagers noticed that the water level in the river rises rapidly due to excessive silt deposition. Analyze the situation and answer:
(i) How does silt deposition contribute to flooding?
(ii) Propose two measures the villagers can take to mitigate this problem.
Answer:

(i) Silt deposition contributes to flooding by:
1. Reducing River Capacity: Silt accumulates on the riverbed, decreasing the depth and volume of the river, causing water to overflow during heavy rains.
2. Blocking Flow: Excessive silt can obstruct natural water channels, forcing water to spread into surrounding areas.

(ii) Two measures to mitigate flooding due to silt deposition are:
1. Constructing Check Dams: Small dams can trap silt upstream, preventing it from reaching the riverbed and maintaining river depth.
2. Afforestation Along Riverbanks: Planting trees near the river reduces soil erosion and silt runoff into the river. Additionally, regular desilting of the riverbed can help maintain its capacity.

Question 20:
A group of students conducted an experiment to study the effect of deforestation on soil erosion. They observed that soil erosion increased significantly in areas where trees were cut down. Based on their findings, answer the following:
(i) Explain the role of trees in preventing soil erosion.
(ii) Suggest two measures to reduce soil erosion in deforested areas.
Answer:

(i) Role of trees in preventing soil erosion: Trees play a crucial role in binding the soil with their root systems, which hold the soil particles together and prevent them from being washed away by wind or water. The canopy of trees also reduces the impact of raindrops on the soil, minimizing soil displacement. Additionally, fallen leaves act as a natural mulch, enriching the soil and improving its water retention capacity.


(ii) Measures to reduce soil erosion in deforested areas:

  • Afforestation: Planting new trees or vegetation helps restore the soil's stability and prevents further erosion.
  • Terracing: Creating steps or terraces on slopes reduces the speed of water flow, minimizing soil loss.
  • Contour Ploughing: Ploughing along the natural contours of the land helps slow down water runoff and retain soil.

These measures not only prevent soil erosion but also promote sustainable land use.

Question 21:
A village near a river faces frequent floods during the monsoon season, leading to loss of topsoil and agricultural damage. The villagers are unaware of sustainable practices to conserve soil. As a science student, suggest and explain two methods they can adopt to protect their soil from erosion during floods.
Answer:

Methods to protect soil from erosion during floods:

  • Building Check Dams: Constructing small dams across seasonal streams or rivers slows down the water flow, allowing soil to settle and reducing erosion. These dams also help recharge groundwater.
  • Planting Riparian Buffers: Growing trees or shrubs along riverbanks stabilizes the soil with their roots and acts as a barrier against floodwater, minimizing soil loss.

Additional Explanation: These methods are cost-effective and environmentally friendly. Check dams trap sediments, while riparian vegetation improves biodiversity and water quality. Educating villagers about these practices ensures long-term soil conservation and sustainable farming.

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