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.

Accepted Answer

(ii). - (ii) To recycle essential nutrients between biotic and abiotic components. - The chapter defines a biogeochemical cycle as the cyclic movement of matter and energy between the abiotic (non-living) and biotic (living) components of the Earth, which keeps carbon, nitrogen and oxygen available to support life. - (i) is wrong — the cycles supply raw materials, not food; only producers actually make food, by photosynthesis. - (iii) is wrong — elements are never created; they are only moved between reservoirs such as air, water, soil, rock and organisms. - (iv) is wrong — removing toxins from inside an organism is excretion, which is not what a biogeochemical cycle does.

Question 2

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 258 Exploration Grade 9

Accepted Answer

- The simulation shows that surface temperature rises as the greenhouse gas concentration is raised — more gas, warmer surface. - Set the concentration slider to a low value: most of the infrared radiated by the ground escapes to space, and the thermometer settles at a low reading. - Slide the concentration up: more infrared is absorbed by the gas and sent back down, the ground receives extra energy, and the thermometer reading climbs. - Compare the built-in presets (ice age / pre-industrial / today): the same Sun gives a colder Earth when the greenhouse gas level is lower. - This is exactly the chapter's mechanism — the surface absorbs sunlight and re-radiates it as infrared, and CO 2, CH 4 and water vapour trap part of that outgoing heat. - Take-away: some greenhouse gas is essential (without it the Earth would be too cold for life), but excess drives global warming.

Question 3

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

Accepted Answer

- The cool mountain breeze lowers the night temperature in the valley and slows moisture loss, which helps both the crop and the soil. - After sunset the mountain slopes lose heat faster than the valley floor; the air above them becomes cool and dense and drains down into the valley as a steady night wind over the fields. - Cooler nights mean less evaporation from the soil and less transpiration from leaves, so the soil holds its moisture longer and needs less irrigation. - The cool, moist air favours dew formation, adding a little extra water to the leaves and the topsoil. - Cool nights relieve the day's heat stress on plants; the large day–night temperature swing this creates is what many hill crops (apple, tea, potato) need for good quality. - By regulating temperature and moisture conditions in this way, mountain breezes support soil and crop health in hilly regions like Shimla and Dehradun.

Question 4

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.

Accepted Answer

(iii). - (iii) The Earth's surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases. - The chapter states that infrared radiation warms the Earth's surface, which then re-radiates this heat back into the atmosphere, and a portion of the outgoing heat is trapped by greenhouse gases such as CO 2, CH 4 and water vapour. - (i) is wrong — CO 2 does not absorb the incoming sunlight; it absorbs the outgoing infrared radiated by the warmed surface. - (ii) is wrong — particles, clouds and gases do absorb and scatter some incoming radiation, but that reduces what reaches the ground; it is not what heats the Earth. - (iv) is wrong — radiation reflected by clouds is sent back towards space, so it is energy lost, not energy that warms the Earth.

Question 5

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? India’s Scientific Contributions Scientists at the Indian Institute of Tropical Meteorology (IITM), Pune, run advanced computer models that couple the energy flows we discussed in this chapter, between atmosphere, oceans, land and ice to simulate the Indian monsoon. These models use data from satellites, buoys in the Indian Ocean, and even stations in Antarctica to improve seasonal forecasts and to study how global warming may change monsoon rainfall patterns across India.

Accepted Answer

- The warm equatorial surface water cools as it travels poleward, becomes denser and sinks, then flows back towards the equator through the deeper levels of the ocean. - The Earth's rotation deflects these moving water masses, so the flow curves into large circular patterns called gyres — clockwise in the Northern Hemisphere, counter clockwise in the Southern Hemisphere. - Impact on the area it reaches: the current carries heat from the equator towards the poles, so the temperature difference across the planet is reduced and high-latitude coasts are made much milder than their latitude would suggest. - Example: the North Atlantic Drift, an extension of the Gulf Stream, flows to the north-western coast of Europe and keeps many ports ice-free during winter even at high latitudes. - This moderating influence also supports human activities such as trade and commerce. - The same currents transport nutrients along their path, supporting massive marine ecosystems.

Question 6

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

Accepted Answer

- Climate change speeds up the water cycle and makes it uneven — more moisture moves through the air, but it is delivered as extremes rather than steady rain. - Heavier rain in some places, drought in others: a warmer atmosphere holds more moisture, so monsoons intensify over some regions while others are left dry. - Melting glaciers: extra meltwater swells rivers now, and in the long run raises sea level, threatening coastal cities such as Mumbai and Chennai. - More run-off, less infiltration: sudden bursts of intense rainfall run off the surface instead of soaking in — this erodes soil and reduces the recharge of groundwater. - Agriculture suffers: with less groundwater stored, sustaining crops through the dry months becomes difficult. - All spheres are linked by it: the disturbed water cycle connects the cryosphere (glaciers), hydrosphere (rivers and oceans), atmosphere (moisture), geosphere (soil erosion and poor infiltration) and biosphere (crops and fisheries).

Question 7

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

Accepted Answer

- Albedo is the fraction of solar radiation that a surface reflects — the higher the albedo, the less radiation is absorbed and the cooler the surface stays. - High albedo keeps a region cold: snow reflects 0.80-0.90 and ice 0.50-0.70 of the incoming radiation, which is a major reason the polar regions are so cold. - Low albedo makes a region warm: black soil, ocean water and crushed rock ( 0.25-0.30 ) reflect little and absorb much, so they heat up quickly — the same reason a dark road becomes hotter than a light-coloured surface, and dark clothes feel hotter than white ones. - Climate effect: these differences in absorption create the uneven heating of the Earth's surface, and that uneven heating is what drives winds and ocean currents. - Feedback effect: warming melts bright snow and ice and exposes darker land and sea beneath; the lowered albedo means still more absorption, which warms the region further. - Human land use changes albedo too: cities of dark concrete and asphalt absorb and re-radiate heat, giving the urban heat island effect, and clearing forests also alters the surface albedo.

Question 8

The CO 2 dissolved in the ocean is disturbed when the global temperature increases. What will happen to marine life?

Accepted Answer

- Marine life is hit from two sides: warm sea water absorbs less CO 2, and the CO 2 that does dissolve makes the water more acidic. - Warmer ocean water reduces the ocean's capacity to act as a carbon sink, so more CO 2 stays in the atmosphere and the warming feeds on itself. - The excess atmospheric CO 2 that is absorbed makes sea water more acidic; this threatens tiny plankton and coral reefs, which need carbonate to build shells and skeletons. - Phytoplankton use the dissolved carbonate and bicarbonate ions for photosynthesis; disturbing this weakens the very base of the marine food chain, so fish and larger animals decline too. - Coral reefs are habitats for a huge number of species — damaging them destroys those habitats and disrupts the whole marine ecosystem. - Coastal fisheries, and the people who depend on them, are affected in turn.

Question 9

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?

Accepted Answer

- Valley breeze (daytime, air flows up the slope): the Sun-facing mountain slopes heat up faster than the valley floor, so the air above them becomes warm and rises, creating a low pressure region; cooler air from the valley then moves up the slopes to replace it. - Mountain breeze (after sunset, air flows down into the valley): the slopes lose heat faster and become cooler while the valley floor stays relatively warmer; the air over the slopes becomes cool and dense and flows down into the valley. - Such daily reversals of wind direction are common in hilly regions like Shimla, Dehradun and other Himalayan valleys. - Yes — the two mountain breezes would differ in temperature. The breeze off the barren rocky mountain would be comparatively warmer (and drier). - Bare rock has a low albedo (crushed rock reflects only 0.25-0.30 ), so during the day it absorbs a large amount of solar radiation and stores heat. - At night the rock re-radiates that stored heat into the air above it — exactly the reason a concrete house feels hot at night while a thick mud-and-wood house stays cool — so the air draining off the rocky slope is warmer. - The grass-covered mountain stays cooler through the day by shade and transpiration and stores less heat, so the air sinking off it at night is cooler; the transpired water vapour also makes that breeze more moist.

Question 10

What would happen to plants and animals on Earth if the biogeochemical cycles were disrupted and stopped? Explain by giving a few examples. Burning of fossil fuels and deforestation saturate natural carbon sinks The overuse of fertilisers in agriculture adds excessive

Accepted Answer

- Life would collapse, because the biogeochemical cycles are what keep returning nutrients to living organisms; if they stopped, each nutrient would be locked in a form no organism could use. - Carbon cycle stops — respiration, decomposition and combustion no longer return CO 2 to the air, so plants run out of raw material for photosynthesis and no food is made for any organism. - Oxygen cycle stops — the O 2 used up by respiration and combustion is not restored by photosynthesis, so plants and animals eventually suffocate. - Nitrogen cycle stops — atmospheric N 2 is non-reactive and cannot be used directly; with no ammonia or nitrate in the soil, plants cannot build proteins and nucleic acids, and animals that eat them are starved of nitrogen too. - Water cycle stops — no evaporation, no clouds, no precipitation; rivers, lakes and groundwater are never refilled, and terrestrial life dries out. - Dead bodies and waste would pile up undecomposed, permanently trapping the nutrients they contain instead of returning them to the soil.

Question 11

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? 266 Exploration Grade 9

Accepted Answer

- Human activities raise greenhouse gases chiefly by burning fossil fuels and clearing forests. - Burning coal, oil and gas for electricity, heating, cooking, transport and industry releases carbon that took millions of years to bury, returning it as CO 2 on a very short time scale. - Deforestation removes the trees that absorb CO 2, and saturates natural carbon sinks like forests and oceans, so more CO 2 stays in the air. - Vehicular emissions add pollutants that react with sunlight to form ground-level smog and ozone. - Overuse of nitrogen fertilisers, and the energy-intensive Haber–Bosch process behind them (about 1-2 % of global energy), add further emissions. - Result: atmospheric CO 2 has risen by about 35 % since 1960, from 315 ppm to 420 ppm. - As an individual I would: walk, cycle or use public transport instead of a private vehicle; switch off lights, fans and appliances when not in use and prefer LED lamps; support solar and other renewable energy at home; plant trees and look after them; save water and avoid wasting food; and reduce, reuse and recycle materials — the mindful lifestyle promoted by Mission LiFE.

Question 12

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?

Accepted Answer

- The troposphere — the lowest layer of the atmosphere, of average height about 12 km — is responsible for winds, storms and rainfall. - Primary reason: it is heated from the Earth's surface below, not directly by the Sun. The ground absorbs solar radiation and warms the air touching it, so temperature in this layer decreases with height at about 6.5^° C per km. - Warm air near the ground is lighter and rises; cooler air moves in to replace it. This convection is what generates winds and storms. - Nearly all the atmosphere's water vapour is in this layer, so evaporation, condensation and precipitation take place here. - Above it, the stratosphere ( 12-50 km) behaves oppositely: the ozone layer absorbs UV, so temperature rises with height. This calms the layer, prevents vertical mixing of air, and keeps weather confined to the troposphere. - The troposphere's height is greatest above the equator and least above the poles, which is why equatorial regions have the most vigorous weather.

Question 13

(iii) 13. Cl -; one; two (ii) Nitrogen dioxide (ii) SO 2 (iv) Cu 2 O (ii) K 2 CO 3 (ii) Ionic

Accepted Answer

- No solution exists for this item — it is not a question. - The text captured under this number is stray OCR from the book's Answer Key section at the back, where two columns of printed answers were read across as a single line. - Chapter 13 prints exactly six Pause and Ponder questions (numbered 1 to 6), ending with question 6 on human activities and greenhouse gases; there is no question 7. - The fragments belong elsewhere: "Anion ( O^2- )", " Cl^-; one; two", "Carbon dioxide / Nitrogen dioxide / Sulfur hexafluoride / Phosphorus trichloride", " NaHCO 3, SO 2, FeCl 3, Cu 2O " and "MO; Ionic" are Chapter 9 answers. - "A - Green curve; B - Red curve; C - Blue curve", "0.01 s", "0.007 s", "0.04 m; 8500 Hz" and "2:9" are Chapter 10 answers. - Recommended action: delete this entry rather than attempt an answer.

Question 14

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

Accepted Answer

- The nitrogen cycle is the overall movement of nitrogen between air, soil, water and organisms; atmospheric N 2 is the largest reservoir but is non-reactive, so it must first be converted into soluble compounds. - Nitrogen fixation — nitrogen-fixing bacteria such as Rhizobium in the root nodules of legumes and Azotobacter in the soil convert atmospheric N 2 into ammonia ( NH 3 ). Lightning fixes a tiny amount as nitrogen oxides, and industrially the Haber–Bosch process does most of it today. - Nitrification — Nitrosomonas converts ammonia into nitrite ( NO 2^- ), and Nitrobacter converts nitrite into nitrate ( NO 3^- ). - Assimilation — plants take up these nitrogen compounds from the soil; animals obtain their nitrogen by eating plants or other animals. - Ammonification — when plants and animals die or produce waste, decomposers such as bacteria and fungi break down the organic matter and return ammonia to the soil. - Denitrification — denitrifying bacteria such as Pseudomonas convert some nitrates back into nitrogen gas, returning it to the atmosphere and completing the cycle. - If nitrogen were not cycled: the huge atmospheric store would stay useless, because N 2 cannot be absorbed directly by plants or animals. - No nitrate or ammonia in the soil means plants cannot synthesise proteins and nucleic acids, so growth, seed formation and crop yields would fail. - Animals, which get all their nitrogen from plants, would be starved of protein, and food chains would collapse. - Nitrogen locked up in dead bodies and waste would never be released back to the soil, so ecosystems could not recover or maintain their balance.

Question 15

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

Accepted Answer

- Oxygen cycle: fewer trees means less photosynthesis, so less O 2 is returned to the atmosphere, while respiration and the combustion of fuels keep on consuming it — the production side of the balance is weakened. - Carbon cycle (uptake): forests are natural carbon sinks; clearing them means less atmospheric CO 2 is drawn down by photosynthesis, and the remaining sinks become saturated. - Carbon cycle (release): the carbon stored in the wood is returned to the air as CO 2 when the trees are burnt or decay, so deforestation is a source of CO 2 as well as a loss of sink. - Net effect: atmospheric CO 2 rises, intensifying the greenhouse effect and global warming — deforestation, along with fossil-fuel burning, is one of the two causes the chapter names for the 35 % rise since 1960. - Less rainfall: reduced transpiration puts less moisture into the air, which can cause a decline in local rainfall. - Altered albedo: removing forest cover changes the fraction of sunlight the surface reflects, changing local heating. - Soil erosion: without tree roots to hold the soil together, erosion increases; run-off rises and infiltration falls. - Loss of biodiversity: habitats are destroyed over time, and many species decline as they lose their natural homes.

Question 16

Explain with suitable diagram the path that carbon takes to go back to the atmosphere. You may start from plants using CO 2 from the atmosphere.

Accepted Answer

- Carbon starts in the air as CO 2, is fixed by plants, and returns to the air by four routes: respiration, decomposition, combustion of fossil fuels, and exchange with ocean water. - Step 1 — Photosynthesis: plants take CO 2 from the atmosphere and, using sunlight, convert it into glucose. - Step 2 — Respiration (fast route, days to years): plants themselves respire and release some CO 2 straight back; animals that eat plants or other animals respire and release CO 2 too. - Step 3 — Decomposition: when plants and animals die, decomposers break down the organic matter and CO 2 returns to the air. - Step 4 — Combustion of fossil fuels (slow route, millions of years): buried dead plants and animals are converted over millions of years into coal, oil and gas; burning these for heating, cooking, transport and industry releases that carbon as CO 2 on a very short time scale. - Step 5 — Ocean exchange: the atmosphere and ocean water continuously exchange CO 2; dissolved CO 2 becomes carbonate and bicarbonate ions used by phytoplankton and by shell-forming organisms, and when they die and sink, carbon is stored on the ocean floor for long periods. What your diagram must show - Draw a closed loop. Put a box at the top labelled " CO 2 in the atmosphere". - A downward arrow from that box to a box "Plants", labelled Photosynthesis. - An arrow from "Plants" to a box "Animals", labelled "feeding". - Two upward arrows back to the CO 2 box — one from "Plants" and one from "Animals" — each labelled Respiration. - Arrows from "Plants" and "Animals" down to a box "Dead plants and animals", then an upward arrow from it to the CO 2 box labelled Decomposition. - A branch from "Dead plants and animals" down to a box "Fossil fuels — coal, oil, gas", labelled "burial over millions of years", and an upward arrow from that box to the CO 2 box labelled Combustion of fossil fuels. - To one side, a box " CO 2 dissolved in ocean water — plankton and shells" joined to the CO 2 box by a double-headed arrow labelled Absorption / release. - Mark the respiration and decomposition arrows as the fast cycle (days to years) and the fossil-fuel branch as the slow cycle (millions of years).

Question 17

Why is an excess of CO 2 in the atmosphere considered undesirable even though it is required by plants?

Accepted Answer

- CO 2 is genuinely needed — plants use it for photosynthesis and it keeps the Earth warm enough to sustain life — but the balance is critical, and an excess breaks it. - Enhanced greenhouse effect: extra CO 2 traps more of the outgoing infrared radiated by the Earth's surface, causing global warming. - Melting ice and rising seas: glaciers and Arctic sea ice melt, sea level rises, and low-lying coastal cities are threatened. - Extreme weather: in India this may mean more intense monsoons (warmer air holds more moisture) and changed rainfall patterns that threaten agriculture. - Ocean acidification: the ocean absorbs the excess CO 2 and sea water becomes more acidic, threatening plankton and coral reefs and disrupting marine ecosystems. - Plants cannot simply mop it up: photosynthesis is limited by water, light, nutrients and available forest area, and deforestation is shrinking that sink even as emissions grow. - Scale of the problem: CO 2 has risen by about 35 % since 1960, from 315 ppm to 420 ppm — a rise unprecedented in the history of human civilisation.

Question 18

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

Accepted Answer

- The Earth's surface loses heat mainly by re-radiating it as infrared radiation into the atmosphere and space. - By day the surface absorbs incoming solar radiation (UV, visible and infrared), warms up, and then radiates that energy back at longer, infrared wavelengths — because all objects radiate heat. - Part of this outgoing infrared is absorbed by the greenhouse gases CO 2, CH 4 and water vapour and sent back down; the rest escapes into space. - A further part of the incoming radiation never heats the surface at all — it is reflected straight back by the surface (its albedo ) and by clouds and the atmosphere. - Significance — energy balance: this outgoing loss balances the energy arriving from the Sun. If heat were not lost, the Earth would go on getting hotter without limit. - Significance — habitable temperature: the partial trapping of the outgoing heat is what keeps the planet warm enough for life; without the atmosphere the Earth would be too cold to live on. - Everyday evidence: a concrete house feels hot at night because the concrete re-radiates the heat it absorbed during the day, while a thick mud-and-wood house stays cool because it re-radiates less.

Question 19

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

Accepted Answer

- On a flat disc facing the Sun, every point would receive the rays at the same angle, so insolation — and therefore temperature — would be nearly the same all over the lit face. - On the actual spherical Earth, the rays strike different latitudes at different angles: near the equator the beam is concentrated over a small area, while near the poles the same beam is spread over a much larger area. - That is exactly why equatorial regions stay relatively warm all year and polar regions stay much colder — the equator-to-pole temperature difference. - On a disc that difference would vanish: no hot equator, no cold poles, and no distinct climate zones by latitude. - With uniform heating there would be no equatorial low, sub-tropical high, sub-polar low or polar high pressure belts, so the planetary winds would not form. - With no planetary winds dragging the surface water, the wind-driven ocean currents and gyres would not form either, and heat would not be carried from equator to poles. - Some uneven heating would remain — land heats faster than water, and dark low-albedo surfaces heat faster than bright ones — but only as local effects, not the global circulation the chapter describes. - (This assumes the disc's flat face is turned towards the Sun. If it were tilted, the whole face would simply be heated less, uniformly, rather than being heated unevenly by latitude.)

Question 20

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

Accepted Answer

- A rise in atmospheric temperature disturbs all three spheres, and each disturbance feeds the next. - Cryosphere — it shrinks. Glaciers, Arctic sea ice and polar ice caps melt faster and snow cover is reduced. - Bright ice and snow have a high albedo ( 0.50-0.90 ); as they melt, darker land and sea water are exposed, which absorb more radiation and warm the region further. - Hydrosphere — more water, moved about more violently. A warmer atmosphere holds more moisture, so evaporation increases, giving heavier rain in some regions and drought in others. - Meltwater adds to rivers and, in the long run, raises sea level, flooding low-lying regions and threatening coastal cities such as Mumbai and Chennai. - Warmer sea water absorbs less CO 2, weakening the ocean as a carbon sink, while the CO 2 it does take up makes it more acidic. - Biosphere — habitat loss and falling biodiversity. Acidic, warmer seas threaten plankton and coral reefs, damaging the base of marine food chains and coastal fisheries. - On land, changed rainfall patterns and intensified monsoons hurt agriculture, and species that cannot move or adapt to the new temperature lose their habitats and decline.

Question 21

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

Accepted Answer

- The atmosphere keeps the Earth's temperature suitable for life by playing two roles at once — it filters what comes in, and it traps part of what goes out. - Role 1, absorbing incoming radiation: the ozone layer in the stratosphere absorbs the harmful short-wavelength UV rays ( 100 nm to 400 nm), and clouds, gases and dust particles absorb or scatter some sunlight before it reaches the ground, so the surface is not scorched. - Because of this, the maximum insolation reaching the surface is only about 1 kWm^-2, lower than the solar constant of about 1.4 kWm^-2 at the top of the atmosphere. - Role 2, trapping outgoing heat: the surface absorbs sunlight and re-radiates it in the infrared, and the greenhouse gases CO 2, CH 4 and water vapour absorb this heat, preventing it from escaping straight into space — the greenhouse effect. - Together these two roles keep both daytime heating and night-time cooling within the range that life can survive; without the atmosphere the Earth would be too cold for life. - The balance is delicate. Venus is hotter than Mercury even though Mercury is nearer the Sun, because Venus has an atmosphere with an uncontrolled greenhouse effect. - Excess CO 2 from human activities enhances the greenhouse effect and causes global warming, which if left unchecked could make the Earth uninhabitable.

Question 22

Describe the interrelationship between different spheres of the Earth. Illustrate with example how these spheres function in a delicate balance. y Consider two hypothetical Earth-sized planets that have an atmosphere. Assume that one planet is entirely covered by oceans and the other is entirely by land. Knowing that the Sun heats the equator more than the poles, how would the wind patterns on these planets compare with the wind systems we observe on Earth, with its combination of land and sea? y Choose any one meal you ate recently (it could be anything, for example, roti and dal, rice and sambar, idli and chutney, and so on). For each main item in the meal, find out and explain: (i) how the carbon in it originally came from carbon dioxide in the air through photosynthesis, and (ii) how the nitrogen in it likely came from the atmosphere into the soil (for example, by bacteria or through the Haber-Bosch process and fertilisers) and then into the plant. Further, list other human activities involved in producing or cooking this meal that add extra carbon dioxide or nitrogen to the environment. y Using data from the India Meteorological Department (IMD, https://mausam.imd.gov.in/) or newspaper records, find the average monsoon rainfall (June - September, or the local season) for your city or district for 5 years during two decades, such as the 1980s and 2020s. Note any trend you may find (increasing or decreasing, or the total number of days) with heavy rain ( 50 mm). How can this be connected to the warmer Arabian Sea temperatures or changes in land use (forests to farms to cities) as discussed in the chapter? The Quest Continues... New tools are allowing scientists to observe the planet in real time and uncover hidden connections between climate, ecosystems, and human activity. What new discoveries will these tools reveal about the changing Earth, and how will they improve our understanding of global warming and climate change?

Accepted Answer

- The Earth's five spheres are joined by continuous flows of energy and matter, so a disturbance in any one sphere produces changes in all the others. - Geosphere — solid rock, soil, landforms such as the Deccan plateau and the Thar desert, and the Earth's interior. - Hydrosphere — liquid water: oceans, rivers such as the Ganga–Brahmaputra system, lakes and groundwater. - Cryosphere — water as ice and snow: Himalayan glaciers, snow in Ladakh, polar ice caps. - Atmosphere — the layer of air held by the Earth's gravity, 78 % nitrogen and 21 % oxygen with argon, CO 2 and water vapour. - Biosphere — all living organisms and their habitats: mangroves, forests, farms, ocean plankton and coral reefs. - Example 1 — snow, lake and grass (Activity 13.1): snow (cryosphere) melts and feeds a lake (hydrosphere); the lake waters the grass (biosphere) that sheep graze. A few winters of poor snowfall lower the lake in summer, so less water reaches the grass and the sheep have less to eat — one small change travels through three spheres. - Example 2 — the monsoon: a warmer atmosphere heats the Arabian Sea (hydrosphere), causing more evaporation and fluctuations in the southwest monsoon; the result is floods in some parts of India and drought in others. The same warming melts glaciers and polar ice (cryosphere), and rising sea level threatens coastal cities and destroys habitats (biosphere). - Example 3 — deforestation: clearing trees (biosphere) reduces transpiration, so local rainfall declines (atmosphere and hydrosphere); without roots the soil erodes (geosphere); and with less photosynthesis, more CO 2 stays in the air, warming the planet further. - Why the balance is delicate: the connecting flows are cyclic — water, carbon, nitrogen and oxygen must keep returning through the biogeochemical cycles. A break anywhere in a cycle does not stay local; it propagates across every sphere.

Question 23

(i) 66 cm 11 cm s (iii) 900 Chapter 5

Accepted Answer

- No solution exists for this item — it is not a question. - Chapter 13's Revise, Reflect, Refine exercises run from 1 to 15 only, ending with question 15 on the interrelationship between the Earth's spheres. - The text captured under this number is stray OCR from the Answer Key at the back of the book. - Specifically, "(i) 66 cm (ii) 14 cm (iii) 11/900 cm s^-1 (iv) 7/2700 cm s^-1 " is the printed answer to Chapter 4, Revise, Reflect, Refine question 16 — a motion problem, not an Earth-system one — and "Chapter 5" is simply the next heading in the key. - Recommended action: delete this entry rather than attempt an answer.

NCERT Solutions · Class 9 Science Earth as a System: Energy, Matter, and Life

Revise, Reflect, Refine 13.1 (part 1 of 11)

Exercise 13.1

Pause and Ponder 13.1–13.2 (part 2 of 11)

Exercise 13.1

Exercise 13.2

Revise, Reflect, Refine 13.2 (part 3 of 11)

Exercise 13.2

Pause and Ponder 13.3 (part 4 of 11)

Exercise 13.3

Revise, Reflect, Refine 13.3–13.4 (part 5 of 11)

Exercise 13.3

Exercise 13.4

Pause and Ponder 13.4 (part 6 of 11)

Exercise 13.4

Revise, Reflect, Refine 13.5 (part 7 of 11)

Exercise 13.5

Pause and Ponder 13.5–13.6 (part 8 of 11)

Exercise 13.5

Exercise 13.6

Revise, Reflect, Refine 13.6 (part 9 of 11)

Exercise 13.6

Pause and Ponder 13.7 (part 10 of 11)

Exercise 13.7

Revise, Reflect, Refine 13.7–13.16 (part 11 of 11)

Exercise 13.7

Exercise 13.8

Exercise 13.9

Exercise 13.10

Exercise 13.11

Exercise 13.12

Exercise 13.13

Exercise 13.14

Exercise 13.15

Exercise 13.16