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CBSE · Class 8 · Science

Our Home: Earth, a Unique Life Sustaining Planet

Standard difficulty · 20 questions · 40 marks

Name: Date: Score: ____ / 40

Show your working for Sections B and C. Answers are on the last page — try every question first!

Section A — Choose the correct answer8 × 1 = 8 marks
1.
The Earth can support life mainly because it is at the right distance from the Sun to have:
  1. no air
  2. very thick clouds
  3. only ice
  4. liquid water
2.
Lakes and ponds belong to the:
  1. atmosphere
  2. geosphere
  3. hydrosphere
  4. biosphere
3.
Which of these is a small, rocky planet?
  1. Saturn
  2. Jupiter
  3. Mercury
  4. Neptune
4.
Potato reproduces mainly by:
  1. vegetative propagation
  2. regeneration
  3. splitting into two
  4. fragmentation
5.
If the Earth's surface were divided into 250 equal squares, about how many would be covered by water (about 70%)?
  1. 250 squares
  2. 75 squares
  3. 125 squares
  4. 175 squares
6.
An amoeba splits into two every day. Starting from one, how many are there after 3 days?
  1. 8 amoebae
  2. 4 amoebae
  3. 6 amoebae
  4. 9 amoebae
7.
The Earth Summit was in 1992 and the Kyoto Protocol in 2005. How many years apart were they?
  1. 92 years
  2. 23 years
  3. 13 years
  4. 14 years
8.
Which of these helps the Earth support life?
  1. a magnetic field
  2. no liquid water
  3. no atmosphere like Mercury
  4. a thick carbon dioxide atmosphere like Venus
Section B — Short answer8 × 2 = 16 marks
9.
Why is the Earth called a unique planet?
10.
Which sphere — atmosphere, hydrosphere, geosphere or biosphere — does each belong to? (a) the ozone layer (b) nitrogen and oxygen gas
11.
Is each planet "rocky" or "gas-rich"? (a) Uranus (b) Jupiter
12.
How does each reproduce (budding, splitting into two, regeneration, fragmentation or vegetative propagation)? (a) money plant (b) ginger
13.
The Paris Agreement aims to keep warming to about 1.5 °C. If the Earth has already warmed by 1.2 °C and warms 0.2 °C every ten years, how much warming is left before the limit, and in about how many years will it be reached?
14.
A bacterium splits into two every 20 minutes. How many bacteria come from one in 300 minutes?
15.
How does each help life on the Earth? (a) the right distance from the Sun (b) liquid water
16.
Which came first, the Montreal Protocol or the Kyoto Protocol, and by how many years?
Section C — Word problems4 × 4 = 16 marks
17.
Explain five reasons why the Earth can support life.
18.
Sort these into the Earth's four spheres: rivers and glaciers, birds, the oceans, the air we breathe. Give one example of two spheres affecting each other.
19.
Why can the Moon not support life as the Earth does? Give two features of the Earth that make life possible.
20.
How do ginger, money plant, amoeba reproduce? How is this different from making seeds in a flower?
AmbifulWorksheets
Practice that never repeats
CBSE · Class 8 · Science

Answer key

Our Home: Earth, a Unique Life Sustaining Planet · AW-8S-OHE-2026-V1 · For parents — fold back or tear off before handing the sheet to your child.

QAnswerWorking
1(d) liquid waterthe habitable zone
2(c) hydrosphere—
3(c) Mercury—
4(a) vegetative propagation—
5(d) 175 squares70% of 250 = 175
6(a) 8 amoebaeit doubles 3 times: 8
7(c) 13 years2005 − 1992
8(a) a magnetic field—
9It is the only planet known to support life.—
10(a) atmosphere (b) atmosphere—
11(a) gas-rich (b) gas-rich—
12(a) vegetative propagation (b) vegetative propagation—
130.3 °C; about 15 years1.5 − 1.2; ÷ 0.2 × 10
1432,768doubles 15 times
15(a) keeps water liquid (b) needed by all living things—
16the Montreal Protocol, by 18 years—
17It is at the right distance from the Sun for liquid water; its nearly circular orbit keeps temperatures steady; its gravity holds an atmosphere with oxygen; the ozone layer blocks harmful UV rays; its magnetic field shields it from harmful particles from space.—
18rivers and glaciers: hydrosphere; birds: biosphere; the oceans: hydrosphere; the air we breathe: atmosphere. For example, rain from the atmosphere wears rocks of the geosphere into soil, or plants (biosphere) take carbon dioxide from the air.—
19the Moon: it has almost no atmosphere and no liquid water. The Earth is at the right distance for liquid water, has an atmosphere with oxygen and an ozone layer, and a magnetic field (also a nearly circular orbit and the right size).—
20ginger: vegetative propagation; money plant: vegetative propagation; amoeba: splitting into two. These need only one parent and give offspring like the parent; seeds come from pollination and fertilisation, mixing features of two parents.—