Download Earth as a System: Energy, Matter and Life Class 9 Science Chapter 9 Questions and Answers PDF

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NCERT Solution for Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life (In-text Exercise)

Below are the detailed Class 9 Science NCERT Solutions Chapter 13 Earth as a System: Energy, Matter and Life. These NCERT Solutions help students understand the concepts easily.

Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life (Think it Over Questions)

Refer to the detailed Think it over questions of NCERT Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life.

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Question: How does the warming of Arabian Sea water affect the southwest monsoon in India?

Answer:

Due to the warming of the Arabian Sea, water evaporation increases, which adds more moisture to monsoon winds. Due to this, the southwest monsoon in India experiences heavy rainfall, cyclones, and irregular distribution of rain.

Question: If a large forest is cleared, how can that affect the flow of a river in that area?

Answer:

The forest plays an important role in maintaining the flow of the river. Because the clearance of forests leads the river to flow irregularly. Forests help in absorbing rainwater without forests, more water flows into rivers, causing floods during rain and reducing water flow during the dry season.

Question: What might happen to coastal cities in India if glaciers and polar ice keep melting faster?

Answer:

If Glaciers and polar ice keep melting faster, then the sea level will rise.

Effects on coastal areas:

1. Melting of glaciers and ice caps leads to flooding in coastal areas

2. Damage to land and infrastructure

3. Coastal areas may face heavy storms

4. Salt water can enter fresh water sources

Question: How would increasing carbon dioxide levels in the atmosphere affect the ocean plankton?

Answer:

Due to an increase in the carbon dioxide level in the atmosphere, the oceans are becoming more acidic, which restricts the growth and survival of plankton.

Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life (Pause and Pounder)

Below are detailed pause and ponder questions from the Class 9 Science NCERT Chapter 13. They are prepared by experts to help students understand the concepts easily.

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Question 1: Visit the website given below and study the effect of the concentration of greenhouse gas on surface temperature, https://phet.colorado. edu/en/simulations/ greenhouse-effect

Answer:

By studying the content given in the PhET Greenhouse effect simulation, the increase in the concentration of greenhouse gases is leading to an increase in Earth's temperature. Greenhouse gases trap more heat in the atmosphere, and the Earth becomes warmer.

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Question 2: How does the cool mountain breeze benefit agriculture activity, particularly the crops and soil?

Answer:

Cool mountain breeze helps in lowering the temperature and reducing evaporation from the soil. Due to which moisture is retained for a longer duration in the soil, and protects the crop from heat, and supports growth.

Question 3: What happens to the warm surface of water from the equator as it travels toward the poles? What impact does this movement have on the area?

Answer:

Water gradually cools when it travels from the equator towards the poles because of this movement, heat transfers to colder regions, leading to the moderation of the climate in coastal areas.

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Question 4: The $\mathrm{CO}_2$ dissolved in the ocean is disturbed when the global temperature increases. What will happen to marine life?

Answer:

Due to an increase in global temperature, the balance of dissolved carbon dioxide in the ocean gets disturbed, making ocean water warmer and more acidic. This can harm marine life by reducing their growth and survival.

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Question 5: What would happen to plants and animals on Earth if the biogeochemical cycles were disrupted and stopped? Explain by giving a few examples.

Answer:

Biogeochemical cycles help plants and animals to get essential nutrients and gases needed for survival. Disruption of the biochemical cycle leads ecosystems to collapse and seriously affects life on Earth.

Example

1. Plants would not get enough carbon dioxide for photosynthesis due to the disruption of the biochemical cycle

2. The nitrogen cycle provides essential nutrients for plant growth. If the cycle stops, then the soil would lose nutrients.

3. This also affects rainfall and causes situations like drought.

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Question 6: Discuss how human activities increase the concentration of greenhouse gases in the atmosphere. What would you do as an individual to reduce the emission of greenhouse gas?

Answer:

Human activities like deforestation, burning of fossil fuels, use of vehicles, etc increases the greenhouse gases like carbon dioxide and methane in the atmosphere. Burning of fossil fuels releases a large amount of carbon dioxide into the atmosphere, and deforestation reduces the number of plants, leading to less absorption of carbon dioxide. Factories and the burning of waste release greenhouse gases. All these gases lead to global warming.

As an individual, things I can do to reduce the emission of greenhouse gas are:

1. Use public transport

2. Saving electricity

3. Planting more trees

Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life (Revise, Reflect, Refine)

Students can refer to the detailed solutions given below for end chapter exercise questions of NCERT Class 9 Science Chapter 13 Earth as a System

Question 1: Choose the most appropriate option to describe the role of biogeochemical cycles in an ecosystem.

(i) To provide food directly to all organisms.

(ii) To recycle essential nutrients between biotic and abiotic components.

(iii) To create new elements for use by living things.

(iv) To remove pollutants and toxins from the organism.

Answer:

To recycle essential nutrients between biotic and abiotic components is correct option because biogeochemical cycle helps in movement and recycling of nutrients like carbon, nitrogen, and oxygen between living organisms and the environment. This cycle is important because it helps in balancing the nutrients in nature and supports life.

Hence, the correct answer is option (ii)

Question 2: Which of the following is primarily responsible for warming of the Earth?

(i) Solar radiation is immediately absorbed by carbon dioxide, which then releases it as heat.

(ii) The atmosphere’s tiny particles absorb incoming solar radiation, which directly heats the Earth.

(iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases.

(iv) The Earth’s environment is heated only by the solar radiation reflected by the clouds.

Answer:

The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases is correct and primarily responsible for warming of the earth. Rays from sun warms earth surface and then redirected towards atmosphere where gases like carbon dioxide and methane absorb the heat causing warming of the earth.

Hence, the correct answer is option (3).

Question 3: Explain how climate change affects the water cycle. Illustrate with examples.

Answer:

The water cycle is affected by changes in climate. Increases in the Earth's temperature make changes in the patterns of evaporation, rainfall, and water availability. Hot climate increases the movement of water through the water cycle and makes weather events more extreme.

The Effects of Climate Change on the Water Cycle are given below:

1. Evaporation increases due to increase in temperature which leads to increase in the amount of water vapour in the atmosphere.

2. Due to climate change, rainfall becomes irregular. Some regions receive very heavy rainfall and floods, while others face less rainfall and droughts.

3. Rise in temperature leads glaciers and ice caps to melt, which in turn increases the water level in oceans.

4. Changes in climate increase the frequency of floods, storms, cyclones, and other natural disasters.

Examples:

It is observed that due to climate changes some parts of country receives more rainfall cause floods while others receive less rainfall causing droughts.

Question 4: Describe how albedo affects the Earth’s surface temperature and its climate.

Answer:

The measurement of amount of sunlight that is reflected back to space by surface is albedo. Surfaces like snow, ice, and clouds are high albedo surfaces because they reflect most of the sunlight, while surfaces like forests, oceans, and dark soil are low albedo surfaces because they absorb more sunlight.

• High albedo surfaces shows cooling effect because they reflect most of the sunlight
• Low albedo surfaces shows warming effect because they absorb most of the sunlight.

Question 5: How are mountain and valley breezes formed? Suppose there are two mountains, one covered with grass and another covered with barren rocks; would the temperature of the two mountain breezes be different? If so, how?

Answer:

Valley Breeze is a daytime breeze, it is formed due to the heating of mountain slopes during the day. The air above the slopes becomes warm and rises upward. Cooler air from the valley moves up the slopes to replace it. Movement of air from the valley towards the mountain is a valley breeze.

Mountain Breeze is a nighttime breeze; it is formed due to the cooling of mountains during the night. The air above the slopes becomes cool and dense, so it flows downward. This movement of cool air from the mountains to the valley is called a mountain breeze.

Yes, the temperature of the breezes would be different for both mountains because the mountain covered with barren rocks would heat up faster during the day and cool down faster at night because rocks absorb and lose heat quickly while the mountain covered with grass would remain relatively cooler during the day and warmer at night because grass retains moisture and heat for longer.

Question 6: You have witnessed weather phenomena, such as winds, storms, rainfall, etc. Which atmospheric layer is mainly responsible for such phenomena and what is the primary reason for its occurrence?

Answer:

The lowest layer of atmosphere, i.e., troposphere, is mainly responsible for weather phenomena like winds, storms, rainfall, clouds, and thunderstorms

Reason for occurrences of the phenomenon in this layer:

• The troposphere contains most of the Earth's air and water vapour
• Troposphere experiences continuous heating and cooling
• It contains dust and gases which are responsible for changes in weather

Question 7: Explain the processes involved in the nitrogen cycle. How would life on Earth be affected if nitrogen were not cycled?

Answer:

Movement of nitrogen between the atmosphere, soil, plants, animals, and microorganisms is the nitrogen cycle. Due to this cycle, nitrogen becomes available to living organisms in useful form

Nitrogen Cycle:

1. Nitrogen Fixation

Most organisms cannot use atmospheric nitrogen directly. Certain bacteria and lightning convert nitrogen gas into ammonia or nitrates that plants can absorb.

2. Nitrification

Ammonia is converted into nitrites and then into nitrates by bacteria present in soil.

3. Assimilation

Nitrates from the soil are absorbed by plants and used to make proteins and other important compounds.

4. Ammonification

Decomposers break down the remains of dead plants and animals and release ammonia back into the soil.

5. Denitrification

Nitrates in the soil are converted back into nitrogen gas by some bacteria, which returns to the atmosphere and completes the cycle.

If nitrogen were not recycled, then plants would not get enough nitrogen to grow properly, which leads to a decrease in crop production. Humans and animals would not get enough nitrogen and waster of dead plants and animals would accmulated.

Question 8: What are the impacts of deforestation on the Earth’s oxygen and carbon cycles? What are the other consequences of deforestation?

Answer:

Trees plays an important role in balancing the oxygen and carbon cycle. Due to deforestation number of trees decreases which will impact oxygen and carbon cycle.

Impact on Oxygen Cycle

Due to deforestation, forests are cut down, and less oxygen is produced because trees release oxygen during photosynthesis. The balance of oxygen in the atmosphere disturbs and affects respiration in living organisms.

Impact on Carbon Cycle

Due to deforestation, forests are cut down, and the number of trees has decreased. Trees absorb carbon dioxide from the atmosphere and store carbon.Burning and cutting trees also release stored carbon back into the atmosphere.

Consequences of Deforestation

1. Loss of Biodiversity

2. Soil Erosion

3. Disturbance in the Water Cycle

4. Increase in Floods and Landslides

Question 9: Explain with suitable diagram the path that carbon takes to go back to the atmosphere. You may start from plants using $\mathrm{CO}_2$ from the atmosphere.

Answer:

During photosynthesis plants use carbon dioxide from the atmosphere to make food.

Path that carbon takes to go back to the atmosphere

1. Plants and animals release carbon dioxide through respiration

2. Bacteria and fungi brakes down dead body parts of plants and animals. During decomposition carbon compounds converted into carbon dioxide and released to atmosphere.

3. Burning of fossil fule releases carbon dioxide in atmosphere.

Question 10: Why is an excess of $\mathrm{CO}_2$ in the atmosphere considered undesirable even though it is required by plants?

Answer:

Plants require carbon dioxide for photosynthesis but excess of carbon dioxide in atmosphere produces green house effect and global warming. Which increase temperature of earth surface and leads to climate changes.

Question 11: How is heat lost from the surface of the Earth? What is its significance?

Answer:

Earth becomes warmer by absorbing heat from sun, this warm surface emits heat back in atmosphere in the form of infrared rays, some heat is escape in space while remaining is trapped by greenhouse gases. This lost in heat helps in maintaining earth temperature, prevents overheating, and supports climate and weather.

Question 12: If the Earth were a flat disc instead of a sphere, how would the patterns of solar radiation and temperature be different?

Answer:

Instead of a sphere, if the Earth were a flat disc, then the pattern of solar radiation and temperature would be different. Due to the spherical shape of earth sunligh falls at different angles, but if earth was flat, then sunlight would fall more evenly on the surface, leading to a decrease in the difference in temperature between regions and tropical, temperate, and polar climate zones would not form properly. Seasons, wind patterns, rainfall, and ocean currents would also affect.

Question 13: Suppose there is a rise in atmospheric temperature on Earth. How would this affect the cryosphere, hydrosphere, and biosphere?

Answer:

Rise in atmospheric temperature would affect the cryosphere, hydrosphere, and biosphere.

1. Cryosphere

Due to an increase in temperature, glaciers, polar ice caps, and snow areas melt faster, which will increase sea levels.

2. Hydrosphere

The water cycle gets disturbed because of the melting of ice, and evaporation increases.

3. Biosphere

Rise in atmospheric temperature leads Animals, Plants and humans to face changes.

Question 14: Explain how the Earth’s atmosphere helps in maintaining a suitable temperature for life to survive on the Earth.

Answer:

With the help of green house effect earth atmosphere maintains a suitable temperature. During the day earth surface absorbs sunlight and becomes warm. At night, heat is released from the Earth's surface in the form of infrared radiation, but greenhouse gases like methane, carbon dioxide, and water vapour trap some heat and prevents complete escaping of heat in the space. This process maintains balance and prevents extreme weather conditions.

Question 15: Describe the interrelationship between different spheres of the Earth. Illustrate with example how these spheres function in a delicate balance.

Answer:

There are 4 major spheres of earth:

1. Atmosphere

2. Hydrosphere

3. Lithosphere

4. Biosphere

All spheres are interconnected and depend on one another to maintain balance on Earth.

The atmosphere provides gases needed by living organisms, the hydrosphere provides water, the lithosphere provides land, soil, minerals, and the biosphere includes all living organisms that interact with the other spheres. Plants in the biosphere absorb water from the hydrosphere and minerals from the lithosphere, while taking carbon dioxide from the atmosphere for photosynthesis. In return, plants release oxygen into the atmosphere and help maintain the carbon and oxygen cycles.

Topics Covered in Class 9 Science Chapter 13 Earth as a System: Energy, Matter, and Life

Given below are all the topics and subtopics that are covered in Earth as a System: Energy, Matter, and Life Class 9 Science Chapter 13 NCERT:

13.1 Uneven Heating of the Earth

• 13.1.1 Interaction of solar radiation on the Earth’s surface
• 13.1.2 Latitude and Earth’s shape
• 13.1.3 Role of the atmosphere

13.2 Uneven Heating Causes Wind and Ocean Currents

• 13.2.1 Local winds
• 13.2.2 Planetary winds
• 13.2.3 Ocean currents

13.3 Biogeochemical Cycles

• 13.3.1 Water cycle
• 13.3.2 Carbon cycle
• 13.3.3 Nitrogen cycle
• 13.3.4 Oxygen cycle

13.4 Human Impact on Earth’s Processes

Also Check

• NCERT Notes for Class 9 Science
• NCERT Syllabus for Class 9 Science

NCERT Solutions for Class 9 Science

Refer to the links given below for detailed solutions of NCERT Class 9 Science. These solutions are prepared by subject experts to help you understand the chapters well and prepare effectively for exams using NCERT.