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.

  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A 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

  1. A the stream beginning to flow uphill
  2. B a rise in the oxygen content of the air
  3. C a change in the length of the day
  4. D less water for drinking and for their crops
Show answer and explanation

Correct answer: D - 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

  1. A fine particles and harmful gases from vehicles and burning waste
  2. B a rise in the amount of nitrogen present in the air
  3. C extra oxygen released by the trees along the roads
  4. D cool 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

  1. A sand forces the plant to make its own soil first
  2. B sand blocks the sunlight from reaching the leaves above
  3. C sand holds far less water and far fewer nutrients than topsoil
  4. D sand contains so much oxygen that the roots are harmed
Show answer and explanation

Correct answer: C - 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

  1. A asking the school to stop giving any written work
  2. B using both sides of every sheet and collecting used paper for recycling
  3. C buying a fresh set of notebooks every month
  4. D burning the old notebooks in the school ground
Show answer and explanation

Correct answer: B - 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

  1. A gives the same brightness while drawing much less electricity
  2. B gives out far more heat than an ordinary bulb does
  3. C generates the electricity it needs as it glows
  4. D works only when there is bright sunlight in the room
Show answer and explanation

Correct answer: A - 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.

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Other subjects

Environment & Ecology 1200 Economy 1075 Logical Reasoning 1013 Quantitative Aptitude 916 Polity & Governance 897 Geography 885 Science & Technology 830 Ancient & Medieval History 737 Art & Culture 711 Modern History 589 International Relations 582 Data Interpretation 515 Reading Comprehension 408 Number Play 317 Fractions 142 A Peek Beyond the Point 125 Light: Shadows and Reflections 120 Quadrilaterals 120 Changes Around Us: Physical and Chemical 120 Proportional Reasoning-1 120 Measurement of Length and Motion 116 Exploring Substances: Acidic, Basic, and Neutral 116 Prime Time 116 Light: Mirrors and Lenses 116 Mindful Eating: A Path to a Healthy Body 115 Exploring Forces 115 Lines and Angles 115 Measurement of Time and Motion 115 Nature's Treasures 115 Parallel and Intersecting Lines 115 Pressure, Winds, Storms, and Cyclones 115 Power Play 114 The Invisible Living World: Beyond Our Naked Eye 112 Working with Fractions 110 Diversity in the Living World 110 A Journey through States of Water 110 A Tale of Three Intersecting Lines 110 The Amazing World of Solutes, Solvents, and Solutions 110 Electricity: Circuits and their Components 110 How Nature Works in Harmony 110 Large Numbers Around Us 110 Nature of Matter: Elements, Compounds, and Mixtures 110 The World of Metals and Non-metals 110 Electricity: Magnetic and Heating Effects 110 We Distribute, Yet Things Multiply 110 A Square and A Cube 109 The Other Side of Zero 106 Heat Transfer in Nature 105 Living Creatures: Exploring their Characteristics 105 Health: The Ultimate Treasure 105 Expressions using Letter-Numbers 105 Methods of Separation in Everyday Life 105 Exploring Magnets 105 Beyond Earth 105 Life Processes in Animals 105 Life Processes in Plants 105 Patterns in Mathematics 103 Perimeter and Area 100 Particulate Nature of Matter 100 Materials Around Us 100 A Story of Numbers 100 Earth, Moon, and the Sun 100