CBSE Class 8 Science Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet — Assertion & Reason
CBSE Class 8 Science Assertion & Reason
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet from the NCERT Class 8 Science textbook Curiosity. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): Earth is the only planet in our solar system where life exists.
Reason (R): Earth is located in the habitable zone where water can exist in liquid form.
Reason (R): Earth is located in the habitable zone where water can exist in liquid form.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Earth's position in the habitable zone ensures temperatures that allow liquid water, which is essential for life as we know it.
2
Assertion (A): Venus is the hottest planet in our solar system.
Reason (R): Venus is the closest planet to the Sun.
Reason (R): Venus is the closest planet to the Sun.
Answer: (c)
A is true, but R is false. Venus is indeed the hottest planet, but NOT because it's closest to the Sun (Mercury is closer). Venus is hottest because its thick carbon dioxide atmosphere traps heat through the greenhouse effect.
3
Assertion (A): Earth's crust is like the thin skin of an apple compared to the planet's size.
Reason (R): All life on Earth exists within this thin layer of the crust.
Reason (R): All life on Earth exists within this thin layer of the crust.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The crust is extremely thin compared to Earth's total size, yet it is where all mountains, oceans, forests, and life exist.
4
Assertion (A): If Earth were much smaller, it would not be able to support an atmosphere.
Reason (R): A smaller Earth would have weaker gravity that couldn't hold gases in the atmosphere.
Reason (R): A smaller Earth would have weaker gravity that couldn't hold gases in the atmosphere.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Earth's size gives it just the right gravitational pull to retain its atmosphere, which is essential for life.
5
Assertion (A): The ozone layer protects life on Earth.
Reason (R): Ozone blocks harmful ultraviolet rays from the Sun.
Reason (R): Ozone blocks harmful ultraviolet rays from the Sun.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The ozone layer acts as a shield, preventing harmful UV radiation from reaching Earth's surface and damaging living cells.
6
Assertion (A): Earth's magnetic field protects life on the planet.
Reason (R): The magnetic field helps us navigate using compasses.
Reason (R): The magnetic field helps us navigate using compasses.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. While the magnetic field does help with navigation, its protective role is much more important—it shields Earth from harmful cosmic rays and solar wind particles.
7
Assertion (A): The greenhouse effect on Earth helps maintain suitable temperatures for life.
Reason (R): Greenhouse gases trap all the heat from the Sun preventing it from escaping.
Reason (R): Greenhouse gases trap all the heat from the Sun preventing it from escaping.
Answer: (c)
A is true, but R is false. The greenhouse effect does help maintain Earth's temperature, but greenhouse gases trap SOME heat, not all—if they trapped all heat, Earth would become too hot like Venus.
8
Assertion (A): Water is essential for life on Earth.
Reason (R): Water is a good solvent and helps transport nutrients in plants and animals.
Reason (R): Water is a good solvent and helps transport nutrients in plants and animals.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Water's role as a solvent and transport medium makes it crucial for biological processes in all living organisms.
9
Assertion (A): The biosphere includes all living organisms on Earth.
Reason (R): The biosphere is limited only to land and does not include oceans.
Reason (R): The biosphere is limited only to land and does not include oceans.
Answer: (c)
A is true, but R is false. The biosphere does include all living organisms, but it encompasses land, water, and air—not just land. Oceans are a major part of the biosphere.
10
Assertion (A): Sexual reproduction produces offspring that are different from their parents.
Reason (R): Offspring receive genetic material from both parents, creating new combinations.
Reason (R): Offspring receive genetic material from both parents, creating new combinations.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The mixing of genetic material from two parents creates variation, making each offspring unique.
11
Assertion (A): Asexual reproduction produces offspring that are exact copies of the parent.
Reason (R): Only one parent is involved in asexual reproduction.
Reason (R): Only one parent is involved in asexual reproduction.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Since there's no mixing of genetic material from two parents, asexual reproduction creates identical copies (clones) of the single parent.
12
Assertion (A): Birds lay eggs while mammals give birth to live young.
Reason (R): In birds, embryo development occurs outside the body after the egg is laid, while in mammals it occurs inside the mother's body.
Reason (R): In birds, embryo development occurs outside the body after the egg is laid, while in mammals it occurs inside the mother's body.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. This difference in reproductive strategy represents two different ways of providing nutrition and protection to developing offspring.
13
Assertion (A): Vegetative propagation is a form of asexual reproduction in plants.
Reason (R): New plants grow from parts like stems, roots, or leaves of a single parent plant.
Reason (R): New plants grow from parts like stems, roots, or leaves of a single parent plant.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Since only one parent is involved and no gametes are formed, vegetative propagation is asexual reproduction.
14
Assertion (A): Climate change is caused by burning fossil fuels.
Reason (R): Burning fossil fuels releases greenhouse gases that trap heat in the atmosphere.
Reason (R): Burning fossil fuels releases greenhouse gases that trap heat in the atmosphere.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The release of carbon dioxide and other greenhouse gases from burning coal, oil, and gas increases atmospheric heat trapping, leading to global warming and climate change.
15
Assertion (A): Biodiversity loss weakens ecosystems.
Reason (R): Every species in an ecosystem has a role, and losing species disrupts the balance of nature.
Reason (R): Every species in an ecosystem has a role, and losing species disrupts the balance of nature.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. When species disappear, food chains are disrupted, and ecosystems lose their resilience and ability to support life effectively.
❓ Frequently Asked Questions
What is covered in CBSE Class 8 Science Chapter 13 Our Home: Earth, a Unique Life Sustaining Planet?
This chapter covers all key topics from Our Home: Earth, a Unique Life Sustaining Planet as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 8 board exam preparation covering the complete syllabus.
Are these CBSE Class 8 Science Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 8 Science?
All chapters of CBSE Class 8 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
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