NCERT Class 9 Science MCQ | Chapter 13: Earth as a System: Energy, Matter, and Life
1. The main source of energy for life on Earth is:
(A) Moon
(B) Sun
(C) Earth’s interior
(D) Ocean currents
Answer: (B)
2. Which of the following is NOT one of the major spheres of the Earth discussed in the chapter?
(A) Geosphere
(B) Hydrosphere
(C) Biosphere
(D) Magnetosphere
Answer: (D)
3. The geosphere includes:
(A) Oceans and rivers
(B) Solid rocks, soil, landforms and Earth’s interior
(C) Air surrounding Earth
(D) All living organisms
Answer: (B)
4. The hydrosphere mainly consists of:
(A) Solid rocks
(B) Liquid water
(C) Air
(D) Living organisms
Answer: (B)
5. The cryosphere represents:
(A) Gaseous water
(B) Solid forms of water
(C) Underground rocks
(D) Living organisms
Answer: (B)
6. Which of the following belongs to the cryosphere?
(A) Ocean
(B) River
(C) Himalayan glacier
(D) Forest
Answer: (C)
7. The biosphere includes:
(A) Only plants
(B) Only animals
(C) All living organisms and their habitats
(D) Only microorganisms
Answer: (C)
8. A disturbance in one Earth sphere can:
(A) Never affect other spheres
(B) Affect other interacting spheres
(C) Affect only the atmosphere
(D) Affect only the biosphere
Answer: (B)
9. Warmer Arabian Sea water can increase:
(A) Evaporation
(B) Freezing
(C) Soil formation
(D) Snowfall directly
Answer: (A)
10. Increased evaporation from the Arabian Sea can influence:
(A) Southwest monsoon
(B) Earth’s rotation
(C) Length of the year
(D) Moon phases
Answer: (A)
11. Solar radiation reaches Earth in the form of:
(A) Sound waves
(B) Electromagnetic waves
(C) Water waves
(D) Mechanical waves
Answer: (B)
12. Electromagnetic waves can travel through:
(A) Vacuum
(B) Only water
(C) Only air
(D) Only solids
Answer: (A)
13. The speed of light in vacuum is approximately:
(A) 3 × 10^6 m/s
(B) 3 × 10^7 m/s
(C) 3 × 10^8 m/s
(D) 3 × 10^9 m/s
Answer: (C)
14. Which electromagnetic radiation has the highest frequency among the following?
(A) Radio waves
(B) Infrared
(C) Visible light
(D) Gamma rays
Answer: (D)
15. Solar radiation reaching Earth is concentrated mainly in:
(A) Gamma, X-ray and radio regions
(B) UV, visible and infrared regions
(C) Radio and microwave regions only
(D) X-rays and gamma rays only
Answer: (B)
16. Visible light from the Sun provides energy for:
(A) Respiration
(B) Photosynthesis
(C) Combustion
(D) Nitrogen fixation only
Answer: (B)
17. Infrared radiation mainly:
(A) Cools the Earth
(B) Warms the Earth’s surface
(C) Produces sound
(D) Produces oxygen directly
Answer: (B)
18. Which gases help trap outgoing infrared radiation?
(A) Oxygen and nitrogen only
(B) Carbon dioxide, methane and water vapour
(C) Hydrogen and helium
(D) Argon only
Answer: (B)
19. UV radiation lies approximately in the wavelength range:
(A) 1–10 nm
(B) 10–50 nm
(C) 100–400 nm
(D) 400–800 nm
Answer: (C)
20. The amount of Sun’s radiation reaching Earth’s surface is called:
(A) Albedo
(B) Insolation
(C) Conduction
(D) Convection
Answer: (B)
21. The approximate value of the solar constant given in the chapter is:
(A) 1.4 W/m²
(B) 14 W/m²
(C) 140 W/m²
(D) 1.4 kW/m²
Answer: (D)
22. Under clear-sky conditions, the maximum insolation reaching Earth’s surface is approximately:
(A) 0.1 kW/m²
(B) 1 kW/m²
(C) 10 kW/m²
(D) 100 kW/m²
Answer: (B)
23. Dark surfaces generally:
(A) Reflect more sunlight
(B) Absorb more sunlight
(C) Reflect all radiation
(D) Remain colder than light surfaces
Answer: (B)
24. The fraction of solar radiation reflected by a surface is called:
(A) Insolation
(B) Albedo
(C) Radiation
(D) Absorption
Answer: (B)
25. A surface with high albedo:
(A) Absorbs more sunlight
(B) Reflects more sunlight
(C) Always becomes hotter
(D) Produces more greenhouse gases
Answer: (B)
26. Snow and ice generally have:
(A) Low albedo
(B) High albedo
(C) Zero albedo
(D) Negative albedo
Answer: (B)
27. Equatorial regions are relatively warmer because:
(A) They receive no sunlight
(B) Solar radiation is concentrated over a smaller area
(C) They are closer to the Moon
(D) They have no atmosphere
Answer: (B)
28. Uneven heating of Earth’s surface helps drive:
(A) Winds and ocean currents
(B) Earth’s rotation
(C) Moon’s revolution
(D) Formation of rocks only
Answer: (A)
29. The atmosphere consists mainly of:
(A) Oxygen and carbon dioxide
(B) Nitrogen and oxygen
(C) Hydrogen and helium
(D) Carbon dioxide and methane
Answer: (B)
30. Approximately what percentage of the atmosphere is nitrogen?
(A) 21%
(B) 50%
(C) 78%
(D) 90%
Answer: (C)
31. Most weather phenomena occur in the:
(A) Stratosphere
(B) Mesosphere
(C) Troposphere
(D) Exosphere
Answer: (C)
32. In the troposphere, temperature generally:
(A) Increases with height
(B) Decreases with height
(C) Remains constant
(D) Becomes zero at all heights
Answer: (B)
33. The ozone layer is mainly located in the:
(A) Troposphere
(B) Stratosphere
(C) Mesosphere
(D) Exosphere
Answer: (B)
34. The ozone layer protects life by absorbing harmful:
(A) Infrared radiation
(B) Radio waves
(C) UV radiation
(D) Sound waves
Answer: (C)
35. Wind is generally the movement of air from:
(A) Low pressure to high pressure
(B) High pressure to low pressure
(C) Cold regions to cold regions only
(D) Ocean to ocean only
Answer: (B)
36. During the day in mountainous regions, warm air over the slopes:
(A) Sinks
(B) Rises
(C) Freezes
(D) Stops moving
Answer: (B)
37. The wind that moves up mountain slopes during the day is called:
(A) Mountain breeze
(B) Valley breeze
(C) Polar wind
(D) Sea breeze
Answer: (B)
38. After sunset, cooler and denser air flows down the slopes. This is called:
(A) Valley breeze
(B) Mountain breeze
(C) Equatorial wind
(D) Ocean current
Answer: (B)
39. Ocean currents are:
(A) Continuous movements of large masses of ocean water
(B) Movements of clouds
(C) Movements of atmospheric gases only
(D) Underground water movements
Answer: (A)
40. Which factor influences ocean currents?
(A) Temperature differences
(B) Salinity differences
(C) Earth’s rotation
(D) All of these
Answer: (D)
41. Water with higher salinity is generally:
(A) Less dense
(B) Denser
(C) Always frozen
(D) Completely immobile
Answer: (B)
42. Large circular patterns formed by ocean currents are called:
(A) Cyclones
(B) Gyres
(C) Monsoons
(D) Tides
Answer: (B)
43. In the Northern Hemisphere, ocean gyres generally rotate:
(A) Clockwise
(B) Counter clockwise
(C) Vertically
(D) Randomly
Answer: (A)
44. A biogeochemical cycle involves the movement of matter between:
(A) Only living organisms
(B) Only rocks
(C) Biotic and abiotic components
(D) Only oceans
Answer: (C)
45. Which of the following is a biogeochemical cycle discussed in the chapter?
(A) Water cycle
(B) Carbon cycle
(C) Nitrogen cycle
(D) All of these
Answer: (D)
46. Plants convert atmospheric carbon dioxide into glucose through:
(A) Respiration
(B) Photosynthesis
(C) Combustion
(D) Decomposition
Answer: (B)
47. Nitrogen-fixing bacteria such as Rhizobium convert atmospheric nitrogen into:
(A) Oxygen
(B) Ammonia
(C) Carbon dioxide
(D) Glucose
Answer: (B)
48. The process by which ammonia is converted into nitrite and then nitrate is called:
(A) Denitrification
(B) Nitrification
(C) Ammonification
(D) Assimilation
Answer: (B)
49. Excessive use of fertilisers can cause algal blooms and oxygen depletion in water bodies. This process is called:
(A) Eutrophication
(B) Photosynthesis
(C) Condensation
(D) Transpiration
Answer: (A)
50. Which of the following can help maintain environmental balance?
(A) Increasing deforestation
(B) Increasing fossil-fuel consumption
(C) Conserving resources and using renewable energy
(D) Increasing waste production
Answer: (C)
NCERT Class 9 Science MCQ | Chapter 13: Earth as a System: Energy, Matter, and Life
ASSERTION–REASON QUESTIONS
Directions:
Choose the correct option:
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
- Assertion (A): A disturbance in one sphere of the Earth can affect other spheres.
Reason (R): The geosphere, hydrosphere, cryosphere, atmosphere and biosphere continuously interact with one another.
Answer: (A)
- Assertion (A): Snow and ice generally remain relatively cool.
Reason (R): Snow and ice have high albedo and reflect a large proportion of incoming solar radiation.
Answer: (A)
- Assertion (A): Solar radiation is distributed evenly over the entire Earth.
Reason (R): The spherical shape of Earth causes the Sun’s rays to strike different latitudes at different angles.
Answer: (D)
- Assertion (A): Most weather phenomena occur in the troposphere.
Reason (R): The troposphere is heated mainly from the Earth’s surface and contains most of the weather processes.
Answer: (A)
- Assertion (A): The ozone layer protects life on Earth from harmful UV radiation.
Reason (R): Ozone in the stratosphere absorbs harmful ultraviolet radiation from the Sun.
Answer: (A)
- Assertion (A): Atmospheric oxygen is restored mainly through photosynthesis.
Reason (R): Respiration and combustion consume oxygen and release carbon dioxide.
Answer: (B)
- Assertion (A): A valley breeze generally blows up the mountain slopes during the day.
Reason (R): During the day, air over the sun-heated slopes becomes warm and rises, creating a low-pressure region.
Answer: (A)
- Assertion (A): Nitrogen gas in the atmosphere can be directly used by plants.
Reason (R): Atmospheric nitrogen is relatively non-reactive and must first be converted into soluble compounds.
Answer: (D)
- Assertion (A): Excess carbon dioxide in the atmosphere can contribute to global warming.
Reason (R): Excess CO2 enhances the greenhouse effect by increasing the trapping of outgoing heat.
Answer: (A)
- Assertion (A): Deforestation can lead to increased soil erosion and a decline in biodiversity.
Reason (R): Removing tree roots reduces their ability to hold soil together and destroys habitats of many species.
Answer: (A)
