Our Home: Earth, a Unique Life Sustaining Planet MCQs for UPSC Prelims
105 practice questions covering Our Home: Earth, a Unique Life Sustaining Planet, organised into 0 topics.
105 questions include a written explanation.
Pick a topic below, or try the samples first.
Sample questions
Q1
hard
Assertion (A): The thinning of the ozone layer is the main cause of global warming. Reason (R): Ozone in the upper atmosphere absorbs ultraviolet radiation from the Sun.
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, because global warming is caused mainly by extra greenhouse gases such as carbon dioxide trapping heat, which is a separate problem from ozone loss. R is true, since absorbing ultraviolet radiation is exactly what the ozone layer does. As A is false the first two choices go, and the third fails because R is true.
Q2
medium
A village depends on a stream that is fed by rainfall. If the rains fail for two years running, the most direct effect on the villagers is
Athe stream beginning to flow uphill
Ba rise in the oxygen content of the air
Cless water for drinking and for their crops
Da change in the length of the day
Show answer and explanation
Correct answer: C - less water for drinking and for their crops
The stream is refilled by rain, so a long dry spell leaves less water for homes and fields. Day length depends on Earth's rotation and is unaffected by rainfall. The oxygen in air does not rise because rain fails, and water cannot flow uphill.
Q3
medium
People in a crowded city complain of coughing and breathlessness on days when a grey haze hangs over the streets. The most likely cause is
Afine particles and harmful gases from vehicles and burning waste
Bextra oxygen released by the trees along the roads
Ca rise in the amount of nitrogen present in the air
Dcool air arriving from the hills nearby
Show answer and explanation
Correct answer: A - fine particles and harmful gases from vehicles and burning waste
A haze of fine particles and gases from exhausts and open burning irritates the airways and makes breathing difficult. Extra oxygen from trees would help rather than harm. The nitrogen share of air barely changes and is harmless to breathe, and cool hill air does not by itself cause coughing.
Q4
hard
Two identical seedlings are planted, one in rich topsoil and the other in washed river sand. Both receive the same water and sunlight, yet the seedling in sand grows poorly. The best explanation is that
Asand blocks the sunlight from reaching the leaves above
Bsand forces the plant to make its own soil first
Csand contains so much oxygen that the roots are harmed
Dsand holds far less water and far fewer nutrients than topsoil
Show answer and explanation
Correct answer: D - sand holds far less water and far fewer nutrients than topsoil
Water drains straight through sand and it carries almost no humus, so the roots find little water and few nutrients. Sunlight falls on the leaves above the ground and is not blocked by what lies below. Roots need air in the soil, so extra oxygen is no problem, and plants do not make soil.
Q5
medium
A group of students want to cut down the paper wasted in their school. The most practical step is
Ausing both sides of every sheet and collecting used paper for recycling
Basking the school to stop giving any written work
Cbuying a fresh set of notebooks every month
Dburning the old notebooks in the school ground
Show answer and explanation
Correct answer: A - using both sides of every sheet and collecting used paper for recycling
Using both sides halves the paper needed, and collecting used sheets sends them back to be made into fresh paper. Stopping written work is not a workable idea in a school. Burning paper pollutes the air, and buying more notebooks increases waste rather than cutting it.
Q6
medium
Replacing ordinary bulbs with LED lamps saves energy because an LED
Agenerates the electricity it needs as it glows
Bgives out far more heat than an ordinary bulb does
Cgives the same brightness while drawing much less electricity
Dworks only when there is bright sunlight in the room
Show answer and explanation
Correct answer: C - gives the same brightness while drawing much less electricity
An LED turns much more of its electricity into light and much less into heat, so it lights a room on a fraction of the power. The ordinary bulb is the one that wastes energy as heat. LED lamps work at any hour, and no lamp generates the electricity it uses.
Practice the full Our Home: Earth, a Unique Life Sustaining Planet bank free
All 105 questions with timed practice, instant scoring, and explanations. Free forever.