Chapter 13: Earth as a System: Energy, Matter, and Life | 50 MCQs | 5 Sets.
Set 1: Earth's Spheres and Solar Energy (Questions 1–10)
1. Which is the primary energy source driving most life processes on Earth?
A. The Moon
B. The Sun
C. Ocean tides only
D. Earth's magnetic field
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Answer: B. The Sun
2. Which Earth sphere includes rocks, soil, mountains and the planet's solid interior?
A. Biosphere
B. Atmosphere
C. Geosphere
D. Hydrosphere
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Answer: C. Geosphere
3. The Earth's hydrosphere includes:
A. Water in oceans, lakes and rivers
B. Only mountain rocks
C. Only gases
D. Only living organisms
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Answer: A. Water in oceans, lakes and rivers
4. Which sphere includes glaciers, ice sheets and sea ice?
A. Biosphere
B. Geosphere
C. Atmosphere
D. Cryosphere
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Answer: D. Cryosphere
5. The biosphere consists of:
A. Only forests
B. Living organisms and the regions where life exists
C. Only ocean water
D. Rocks and minerals only
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Answer: B. Living organisms and the regions where life exists
6. Why are Earth's spheres considered interconnected?
A. They never exchange matter
B. Only living things affect them
C. Changes in one sphere can influence others
D. They function independently
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Answer: C. Changes in one sphere can influence others
7. Solar energy travels from the Sun to Earth mainly through:
A. Electromagnetic radiation
B. Sound waves
C. Ocean currents
D. Direct particle contact
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Answer: A. Electromagnetic radiation
8. Which type of wave can travel through the vacuum of space?
A. Sound waves
B. Water waves
C. Seismic waves
D. Electromagnetic waves
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Answer: D. Electromagnetic waves
9. The approximate speed of light in a vacuum is:
A. 3 × 10⁶ m/s
B. 3 × 10⁸ m/s
C. 3 × 10⁴ m/s
D. 3 × 10² m/s
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Answer: B. 3 × 10⁸ m/s
10. Which process uses energy from sunlight to make food in green plants?
A. Respiration
B. Decomposition
C. Photosynthesis
D. Transpiration
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Answer: C. Photosynthesis
Set 2: Radiation, Temperature and the Atmosphere (Questions 11–20)
11. Which electromagnetic radiation is mainly associated with the transfer of heat?
A. Infrared radiation
B. Sound radiation
C. Seismic radiation
D. Water waves
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Answer: A. Infrared radiation
12. Which gases contribute to the greenhouse effect by absorbing outgoing infrared radiation?
A. Nitrogen only
B. Oxygen only
C. Helium and neon
D. Carbon dioxide, methane and water vapour
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Answer: D. Carbon dioxide, methane and water vapour
13. The fraction of incoming solar energy reflected by a surface is called:
A. Insolation
B. Albedo
C. Conduction
D. Evaporation
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Answer: B. Albedo
14. Which surface usually reflects a larger proportion of sunlight?
A. Dark asphalt
B. Black soil
C. Fresh snow
D. Dark forest floor
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Answer: C. Fresh snow
15. Insolation refers to:
A. Incoming solar radiation received by a surface
B. Heat produced only inside Earth
C. Energy from ocean tides only
D. Sound energy in the atmosphere
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Answer: A. Incoming solar radiation received by a surface
16. Why do equatorial regions generally receive more intense sunlight than polar regions?
A. They have no atmosphere
B. They are much closer to the Sun
C. They receive sunlight only at night
D. Sunlight is more directly concentrated over a smaller area
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Answer: D. Sunlight is more directly concentrated over a smaller area
17. Approximately what percentage of dry air in Earth's atmosphere is nitrogen?
A. 21%
B. 78%
C. 50%
D. 1%
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Answer: B. 78%
18. Most clouds, storms and everyday weather events occur in the:
A. Exosphere
B. Mesosphere
C. Troposphere
D. Thermosphere
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Answer: C. Troposphere
19. The ozone layer is mainly found in which atmospheric layer?
A. Stratosphere
B. Troposphere
C. Exosphere
D. Lowest ocean layer
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Answer: A. Stratosphere
20. The ozone layer is important because it absorbs much of the Sun's harmful:
A. Sound energy
B. Radio waves
C. Visible light
D. Ultraviolet radiation
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Answer: D. Ultraviolet radiation
Set 3: Winds, Water and Ocean Currents (Questions 21–30)
21. Wind is the movement of air mainly caused by differences in:
A. Soil colour
B. Atmospheric pressure
C. Rock hardness
D. Ocean depth alone
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Answer: B. Atmospheric pressure
22. During a sunny day, air over a heated mountain slope tends to:
A. Become denser and sink
B. Turn into liquid
C. Warm up and rise
D. Stop moving permanently
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Answer: C. Warm up and rise
23. What is the name for the daytime wind that flows up mountain slopes?
A. Valley breeze
B. Mountain breeze
C. Polar easterly
D. Trade wind
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Answer: A. Valley breeze
24. After sunset, cooler air flowing down a mountain slope produces a:
A. Valley breeze
B. Sea breeze
C. Valley updraft
D. Mountain breeze
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Answer: D. Mountain breeze
25. Ocean currents are best described as:
A. Stationary masses of water
B. Large-scale movements of ocean water
C. Movements of rocks beneath the sea
D. Clouds moving above oceans
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Answer: B. Large-scale movements of ocean water
26. Which factor can influence the movement of ocean currents?
A. Differences in water temperature
B. Differences in salinity
C. Earth's rotation
D. All of these
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Answer: D. All of these
27. Compared with less salty seawater at the same temperature, more saline seawater is generally:
A. Less dense
B. Always gaseous
C. More dense
D. Completely motionless
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Answer: C. More dense
28. Large circular systems of ocean currents are called:
A. Gyres
B. Glaciers
C. Estuaries
D. Aquifers
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Answer: A. Gyres
29. In the Northern Hemisphere, major subtropical ocean gyres generally rotate:
A. Only vertically
B. Counterclockwise in every case
C. Without any pattern
D. Clockwise
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Answer: D. Clockwise
30. The continuous movement of water between Earth's surface and the atmosphere is called the:
A. Nitrogen cycle
B. Water cycle
C. Rock cycle
D. Food chain
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Answer: B. Water cycle
Set 4: Water, Carbon and Nitrogen Cycles (Questions 31–40)
31. The change of liquid water into water vapour is called:
A. Condensation
B. Precipitation
C. Evaporation
D. Freezing
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Answer: C. Evaporation
32. The process in which water vapour cools and forms liquid droplets is:
A. Condensation
B. Transpiration
C. Infiltration
D. Runoff
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Answer: A. Condensation
33. Rain, snow and hail falling from clouds are forms of:
A. Evaporation
B. Photosynthesis
C. Infiltration
D. Precipitation
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Answer: D. Precipitation
34. Plants release water vapour mainly through tiny openings in their leaves called:
A. Roots
B. Stomata
C. Petals
D. Xylem vessels only
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Answer: B. Stomata
35. The cycling of carbon between living organisms and the non-living environment is called the:
A. Water cycle
B. Rock cycle
C. Carbon cycle
D. Lunar cycle
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Answer: C. Carbon cycle
36. Which process removes carbon dioxide from the atmosphere and incorporates carbon into plant matter?
A. Photosynthesis
B. Combustion
C. Respiration
D. Decomposition alone
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Answer: A. Photosynthesis
37. Which activities release carbon dioxide into the atmosphere?
A. Photosynthesis only
B. Water absorption by roots only
C. Condensation only
D. Burning fossil fuels and respiration
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Answer: D. Burning fossil fuels and respiration
38. Why is atmospheric nitrogen not directly usable by most plants?
A. It contains no atoms
B. It must generally be converted into usable nitrogen compounds
C. It exists only in oceans
D. It is a liquid at room temperature
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Answer: B. It must generally be converted into usable nitrogen compounds
39. Rhizobium bacteria help leguminous plants by:
A. Producing sunlight
B. Breaking down rocks into metals
C. Fixing atmospheric nitrogen
D. Stopping root growth
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Answer: C. Fixing atmospheric nitrogen
40. The conversion of ammonia into nitrites and nitrates by microorganisms is known as:
A. Nitrification
B. Denitrification
C. Evaporation
D. Transpiration
Show Answer
Answer: A. Nitrification
Set 5: Environmental Balance and Applications (Questions 41–50)
41. The conversion of nitrates into nitrogen gas by certain microorganisms is called:
A. Nitrification
B. Denitrification
C. Photosynthesis
D. Condensation
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Answer: B. Denitrification
42. What can happen when excessive fertiliser enters a lake?
A. All nutrients disappear immediately
B. The water becomes permanently sterile
C. The water cycle stops
D. Excessive algae may grow and oxygen levels may fall
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Answer: D. Excessive algae may grow and oxygen levels may fall
43. The excessive enrichment of water with nutrients, often leading to algal blooms, is called:
A. Eutrophication
B. Condensation
C. Infiltration
D. Weathering
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Answer: A. Eutrophication
44. Which is a likely environmental effect of large-scale deforestation?
A. Increased habitat availability in all cases
B. Elimination of soil erosion
C. Greater soil erosion and habitat loss
D. Complete prevention of flooding
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Answer: C. Greater soil erosion and habitat loss
45. Which human activity increases the amount of carbon dioxide in the atmosphere?
A. Protecting forests
B. Burning coal, oil and natural gas
C. Restoring wetlands
D. Planting native trees
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Answer: B. Burning coal, oil and natural gas
46. An increase in greenhouse gases can lead to:
A. The permanent disappearance of sunlight
B. A complete stop to evaporation
C. The disappearance of Earth's atmosphere
D. An increase in global average temperature
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Answer: D. An increase in global average temperature
47. Which action can help reduce pressure on natural ecosystems?
A. Conserving water and protecting habitats
B. Dumping waste into rivers
C. Clearing forests unnecessarily
D. Increasing single-use waste
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Answer: A. Conserving water and protecting habitats
48. Why are biogeochemical cycles essential for life?
A. They destroy all nutrients
B. They stop matter from moving
C. They recycle essential elements through ecosystems
D. They replace the need for energy
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Answer: C. They recycle essential elements through ecosystems
49. Which energy source is renewable?
A. Coal
B. Solar energy
C. Petroleum
D. Natural gas
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Answer: B. Solar energy
50. Which statement best explains why Earth's systems must be studied together?
A. Each sphere has no effect on another
B. Only the atmosphere supports life
C. Matter never cycles between systems
D. Energy and matter move between interconnected spheres
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Answer: D. Energy and matter move between interconnected spheres