Chapter Exam

Chapter-13 Earth — Online MCQ Test

Q: What percentage of Earth's surface is covered by water?

Answer: B. About 71% — Approximately 71% of Earth's surface is covered by water, making it the 'Blue Planet'. The remaining 29% consists of land.

SCIENCE · Grade 8 · CBSE(NCERT)

Practice Chapter-13 Earth with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 8 SCIENCE. This chapter covers: a Unique Life Sustaining Planet. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-13 Earth — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 8 SCIENCE — Chapter-13 Earth, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is the primary reason Earth is called a unique life-sustaining planet?

A. It has the largest size among all planets
B. It has liquid water, suitable temperature, and atmosphere ✓
C. It is closest to the Sun
D. It has the most number of moons

Answer: B. It has liquid water, suitable temperature, and atmosphere
Earth sustains life due to the presence of liquid water, moderate temperatures within the biosphere, and a protective atmosphere containing oxygen and nitrogen.

What percentage of Earth's surface is covered by water?

A. About 50%
B. About 71% ✓
C. About 85%
D. About 95%

Answer: B. About 71%
Approximately 71% of Earth's surface is covered by water, making it the 'Blue Planet'. The remaining 29% consists of land.

Why is Earth's atmosphere important for sustaining life?

A. It only provides oxygen for respiration
B. It protects from harmful radiations, maintains temperature, and provides gases for respiration ✓
C. It only creates weather
D. It only reflects sunlight

Answer: B. It protects from harmful radiations, maintains temperature, and provides gases for respiration
Earth's atmosphere serves multiple functions: it provides oxygen for respiration, protects from UV and cosmic radiation, maintains suitable temperature through greenhouse effect, and supports the water cycle.

Analyze: Why is biodiversity important for Earth's life-sustaining capacity?

A. Biodiversity is only for aesthetic purposes
B. Different species perform different ecological functions, maintain ecosystem balance, and ensure survival through genetic variation ✓
C. Biodiversity makes the planet heavier
D. Biodiversity is harmful to life

Answer: B. Different species perform different ecological functions, maintain ecosystem balance, and ensure survival through genetic variation
Biodiversity ensures ecosystem stability by distributing ecological roles among species, providing resilience to environmental changes, and maintaining genetic resources for adaptation.

TRICKY: Which of these statements about Earth's uniqueness is MOST accurate?

A. Earth is the only planet with an atmosphere
B. Earth is the only planet with surface water due to its unique position, temperature, and atmospheric composition ✓
C. Earth is the hottest planet
D. Earth has the thickest atmosphere

Answer: B. Earth is the only planet with surface water due to its unique position, temperature, and atmospheric composition
While other planets have thin atmospheres and some water (frozen or subsurface), Earth is uniquely positioned in the habitable zone with conditions allowing abundant liquid surface water.