Earth as a System: Energy, Matter, and Life MCQs for UPSC Prelims
125 practice questions covering Earth as a System: Energy, Matter, and Life, organised into 1 topics.
125 questions include a written explanation.
Pick a topic below, or try the samples first.
Almost all weather phenomena such as clouds, rain and storms occur in one layer of the atmosphere. Which layer is it?
AThe stratosphere
BThe mesosphere
CThe troposphere
DThe exosphere
Show answer and explanation
Correct answer: C - The troposphere
Nearly all weather takes place in the troposphere, the lowest layer, which reaches an average height of about $12\ \text{km}$ and is heated from the Earth's surface below. The stratosphere above it holds the ozone layer and stays calm, with almost no weather. The mesosphere and the exosphere lie much higher still and play only a minor role in the climate at the surface.
Q2
hard
Assertion (A): Burning fossil fuels removes carbon dioxide from the atmosphere. Reason (R): The carbon in coal, oil and gas came originally from plants and animals that were buried long ago.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: D - A is false, but R is true
(A) is false. Burning fossil fuels does the opposite, releasing stored carbon back into the air as carbon dioxide. (R) is true, because coal, oil and gas formed from plants and animals that were buried and altered over millions of years. That buried carbon is exactly what combustion sends back up, which is why the assertion has the direction reversed.
Q3
medium
Ozone is described as protective in one place and harmful in another. Which statement captures this correctly?
AOzone in the stratosphere damages health, while ozone near the ground blocks ultraviolet rays
BOzone in the stratosphere blocks ultraviolet rays, while ozone near the ground damages health
COzone is harmful wherever it is found, including in the stratosphere
DOzone is protective wherever it is found, including near the ground
Show answer and explanation
Correct answer: B - Ozone in the stratosphere blocks ultraviolet rays, while ozone near the ground damages health
High in the stratosphere ozone absorbs harmful ultraviolet radiation and shields living things. Near the ground it forms from vehicle emissions reacting with sunlight and is bad for health. Swapping the two places reverses both facts. Where the ozone sits is exactly what decides whether it helps or harms.
Q4
medium
In the troposphere the temperature falls by about $6.5\ ^\circ\text{C}$ for every kilometre of height, while in the stratosphere it rises with height. What causes the rise in the stratosphere?
AThe stratosphere is closer to the Sun, so it receives more radiation on each square metre
BWarm air from the troposphere rises freely into the stratosphere and heats it
COzone there absorbs ultraviolet rays and heats that part of the atmosphere
DWater vapour in the stratosphere condenses and releases heat continuously
Show answer and explanation
Correct answer: C - Ozone there absorbs ultraviolet rays and heats that part of the atmosphere
The ozone layer sits in the stratosphere, and ozone absorbs ultraviolet radiation, which warms the air there, so temperature climbs with height. Being a few tens of kilometres nearer the Sun makes no measurable difference to the radiation received. The warming with height actually calms the layer and stops vertical mixing, so tropospheric air does not rise freely into it. Condensation and weather are confined to the troposphere.
Q5
easy
India's abundant sunshine drives one large seasonal wind system that shapes the country's climate and farming. Which system is this?
AThe urban heat island
BThe North Atlantic Drift
CThe southwest monsoon
DThe mountain breeze of the Himalayas
Show answer and explanation
Correct answer: C - The southwest monsoon
Solar insolation over India, which lies in the tropical and sub-tropical regions, drives the southwest monsoon, and that monsoon governs the country's climate and agriculture. The North Atlantic Drift is a warm ocean current off Europe. A mountain breeze is a small local wind that reverses every day. An urban heat island is a patch of extra warmth over a city rather than a wind system.
Q6
medium
Consider these statements about the Earth's shape and its heating. (i) The spherical shape of the Earth makes the Sun's rays strike different latitudes at different angles. (ii) The tilt of the Earth's axis, together with its shape, gives rise to the seasons. Which is correct?
ANeither (i) nor (ii) is correct
BOnly (ii) is correct
CBoth (i) and (ii) are correct
DOnly (i) is correct
Show answer and explanation
Correct answer: C - Both (i) and (ii) are correct
Both statements hold. Because the Earth is a sphere, sunlight arrives almost head on near the equator and at a steep slant near the poles, which is why the two regions are heated so unequally. The spherical shape together with the tilt of the Earth's axis also produces the seasons and the changing length of daytime through the year. Neither statement can be rejected.
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