Our Home: Earth, a Unique Life Sustaining Planet MCQs (Class 8 Science, NCERT)

105 practice questions on Our Home: Earth, a Unique Life Sustaining Planet, a chapter in the NCERT Class 8 Science textbook. Every question includes a written explanation. Try the samples below - the answer stays hidden until you ask for it.

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 less water for drinking and for their crops
  4. D a 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
  1. A fine particles and harmful gases from vehicles and burning waste
  2. B extra oxygen released by the trees along the roads
  3. C a rise in the amount of nitrogen present in the air
  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 blocks the sunlight from reaching the leaves above
  2. B sand forces the plant to make its own soil first
  3. C sand contains so much oxygen that the roots are harmed
  4. D sand 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
  1. A using both sides of every sheet and collecting used paper for recycling
  2. B asking the school to stop giving any written work
  3. C buying a fresh set of notebooks every month
  4. D burning the old notebooks in the school ground so that they take up no space
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
  1. A generates the electricity it needs as it glows
  2. B gives out far more heat than an ordinary bulb does
  3. C gives the same brightness while drawing much less electricity
  4. D works 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.

Start practicing I am a teacher - create a test

More Class 8 Science chapters

The Invisible Living World: Beyond Our Naked Eye 112 Health: The Ultimate Treasure 105 Electricity: Magnetic and Heating Effects 110 Exploring Forces 115 Pressure, Winds, Storms, and Cyclones 115 Particulate Nature of Matter 100 Nature of Matter: Elements, Compounds, and Mixtures 110 The Amazing World of Solutes, Solvents, and Solutions 110 Light: Mirrors and Lenses 116 How Nature Works in Harmony 110