Class 8 Science Curiosity Chapter 13 Solutions (NCERT 2026–27) – Our Home: Earth, a Unique Life Sustaining Planet

These Class 8 Science Curiosity Chapter 13 solutions cover Our Home: Earth, a Unique Life Sustaining Planet from the new NCF-2023 textbook (2026–27), with every “Keep the curiosity alive” question answered step by step.

Class: 8 Subject: Science Book: Curiosity Chapter: 13 Exercise: Keep the curiosity alive (12 Qs) Session: 2026–27
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Class 8 Science Curiosity Chapter 13 Solutions – Overview

Chapter 13 of Curiosity, Our Home: Earth, a Unique Life Sustaining Planet, is the concluding chapter of the Grade 8 book. It explains why Earth is the only known planet that supports life: its position in the habitable (Goldilocks) zone where water stays liquid, its right size to hold an atmosphere by gravity, the protective ozone layer, and the Earth’s magnetic field that shields us from cosmic rays and solar wind. It then shows how the atmosphere, hydrosphere, geosphere and biosphere interact to sustain life, how reproduction (asexual and sexual) keeps life going, and how the triple planetary crisis—climate change, biodiversity loss and pollution—threatens this delicate balance. These Class 8 Science Curiosity Chapter 13 solutions answer every textbook question step by step.

Key Concepts & Definitions

Habitable zone (Goldilocks zone): the range of distances from the Sun (or a star) where the temperature lets water stay as a liquid — neither too hot nor too cold. Earth lies in this zone.

Greenhouse effect: gases like carbon dioxide trap heat radiated by the warmed Earth, keeping it warm enough for liquid water. A mild greenhouse effect is helpful; too much (as on Venus) makes a planet too hot.

Crust & geosphere: the thin solid outer layer where all life exists; the solid parts of Earth (rocks, soil, minerals) make up the geosphere.

The four spheres: atmosphere (air), hydrosphere (water), geosphere (solid Earth), biosphere (all living things and their habitats) — they interact to sustain life.

Ozone layer: a layer formed from ozone (a three-atom oxygen molecule) that shields the Earth from harmful ultraviolet (UV) rays.

Magnetic field: produced by movement of molten iron in Earth’s core; it deflects cosmic rays and the solar wind, protecting the atmosphere and life.

Reproduction: ensures continuity of life. Asexual — one parent, identical offspring (e.g. vegetative propagation). Sexual — two parents, gametes carry half the genetic material, offspring show variation.

Triple planetary crisis: climate change, biodiversity loss and pollution — the biggest threats to life on Earth.

“Probe and Ponder” & Activity — Answers

What do you think Earth would look like if there were no life on it at all?

ANSWERIt would look like a barren, rocky planet — bare land, no green forests or grass, no animals or people. Without plants there would be little free oxygen, the air and water would be unused by living things, and the surface would resemble lifeless worlds like Mars or the Moon.

Life on Earth has survived for billions of years. What allows it to keep going despite major changes and disasters?

ANSWERReproduction keeps each kind of organism continuing, and the variation produced by sexual reproduction lets life adapt to new conditions. Earth’s stable habitable conditions (liquid water, atmosphere, ozone layer, magnetic field) and the balanced interaction of its spheres also help life recover after changes.

Why don’t dogs lay eggs? Or hens give birth to live chicks?

ANSWERDifferent animals have different reproductive strategies. In most mammals like dogs, the zygote develops into an embryo inside the mother’s body, which supplies food and oxygen until birth. In birds like hens, the fertilised egg is laid and the embryo develops outside, using the food stored in the egg until it hatches.

If a spaceship carried soil and water to Mars, could plants start growing there?

ANSWERSoil and water alone are not enough. Mars has a very thin atmosphere (about 100 times thinner than Earth’s) with little oxygen, much colder temperatures, weak protection from harmful radiation, and no ozone layer. Plants would also need a suitable air supply, warmth, sunlight and shelter, so growing them on Mars would be extremely difficult without recreating Earth-like conditions.

Activity 13.1: List some features of the Earth that we often take for granted, but are interesting and important to us.

ANSWER Some examples beyond those given in the book: (3) Liquid water is available almost everywhere for drinking and growing crops. (4) The temperature stays moderate, so water does not all freeze or boil away. Other valid features: oxygen in the air lets us breathe; the ozone layer blocks harmful UV rays; the magnetic field protects us from harmful space particles; seasons repeat in a steady cycle; soil and minerals supply food and building materials.

Class 8 Science Curiosity Chapter 13 Solutions — Keep the Curiosity Alive

1. What is one major reason Mars cannot currently support life like Earth? (i) It has too many volcanoes.(ii) It is too close to the Sun.(iii) It lacks a thick atmosphere and liquid water.(iv) Its magnetic field is too strong.

ANSWER (iii) It lacks a thick atmosphere and liquid water. Mars’ atmosphere is about 100 times thinner than Earth’s and it has no stable liquid water on its surface today, so it cannot support life as we know it.

2. Which of these is an example of geodiversity? (i) Variety of bird chirping in a forest.(ii) Different landforms like mountains, valleys, and deserts.(iii) Changing weather during monsoons.(iv) Number of different types of fish in a pond.

ANSWER (ii) Different landforms like mountains, valleys, and deserts. Geodiversity is the variety of landforms, rocks and soils, together with the processes that shape them. Options (i) and (iv) describe living variety (biodiversity) and (iii) describes weather.

3. If the Earth were smaller with the same density, what might happen to its atmosphere? (i) It would become thicker and hotter.(ii) It would escape into space due to weaker gravity.(iii) It would become frozen.(iv) It would cause stronger winds.

ANSWER (ii) It would escape into space due to weaker gravity. A smaller planet (same density) has weaker gravity, which would not be able to hold on to the gases of the atmosphere — they would drift away into space, as has largely happened on Mars and Mercury.

4. In sexual reproduction, why are offspring different from their parents? (i) They grow in different climates.(ii) They eat different food.(iii) They acquire new instructions after birth.(iv) They get mixed instructions (genes) from both parents.

ANSWER (iv) They get mixed instructions (genes) from both parents. In sexual reproduction the gametes from two parents combine, so the offspring inherit a new mix of genetic instructions — sharing some traits with each parent but also showing differences (variation).

5. You notice tiny green plants growing in cracks on your school wall after the monsoon. Where do you think the seeds came from? What conditions helped these plants grow there?

ANSWER Where the seeds came from: the seeds were most likely carried to the wall by wind, by birds or animals (which eat fruits and drop the seeds in their droppings), or by water splashing during the rains. They lodged in the cracks where a little dust and soil had collected. Conditions that helped them grow: the monsoon water reached the seeds, and along with air, warmth and sunlight and a tiny amount of soil in the crack, this gave the seeds the conditions they needed to germinate, develop roots and shoots, and grow into small plants.

6. A city has recently cut down a large patch of forest to build new roads and buildings. Discuss the possible effects this could have on the local climate and biodiversity? How might this affect water availability or quality in the area?

ANSWER Effect on local climate: trees absorb carbon dioxide and release water vapour, so cutting them can make the area hotter and drier, reduce rainfall, and increase carbon dioxide, adding to global warming. Effect on biodiversity: the forest is a habitat for many plants, animals, birds and insects. Destroying it removes their food and shelter, so many species may disappear or move away, upsetting food chains (for example herbivores lose plants, and predators then lose prey). Effect on water: without roots and leaf litter, rainwater runs off quickly instead of soaking in, so groundwater is not recharged and water becomes scarcer. Bare soil is washed into streams, while dust, oil and waste from roads and buildings can pollute the water, reducing its quality.

7. A friend says, “The Earth has always had climate changes in the past, so today’s global warming is nothing new.” How would you respond using what you’ve learnt in this and other chapters of your science book?

ANSWER It is true that Earth’s climate has changed naturally in the past, but today’s warming is different because it is happening very fast and is caused mainly by human activities. Burning fossil fuels like coal and oil releases extra carbon dioxide and methane that were locked underground for millions of years. These greenhouse gases trap more heat, so the Earth cannot absorb the carbon fast enough and the temperature rises quickly — melting ice caps, raising sea levels and causing extreme weather. Because the change is rapid, many plants and animals cannot adapt in time. So today’s global warming is a serious, human-caused problem that needs urgent action, not something to ignore.

8. Imagine Earth’s magnetic field suddenly disappeared. What kinds of problems could arise for life on Earth? Explain.

ANSWER The magnetic field acts like a protective shield that deflects harmful high-energy particles — cosmic rays from across the universe and the solar wind from the Sun. If it vanished, these particles would strike the Earth directly. They could damage and strip away the atmosphere, thin the ozone layer, and let in more harmful UV radiation. This could harm living cells, increase diseases, damage crops and electronic systems, and over time make the Earth far less able to support life.

9. You are tasked with designing a new settlement for humans on Mars. Name three things you would need to recreate from Earth to support human life there. Which of these do you think is the hardest to replicate, and why?

ANSWER Three things to recreate: (1) a breathable atmosphere with enough oxygen and the right pressure; (2) a steady supply of liquid water; (3) a warm, stable temperature with protection from harmful radiation (an ozone-like shield or a magnetic shield). Food production (soil and plants) is also needed. Hardest to replicate: a protective atmosphere with radiation shielding is the most difficult. We could carry tanks of water and heaters, but covering an entire planet with a thick, oxygen-rich atmosphere held by gravity and protected by a magnetic field is enormously hard, because Mars’ weak gravity cannot hold a thick atmosphere and it lacks a strong magnetic field.

10. In a village, the temperature has been increasing and rainfall has become unpredictable over the past few years. What could be causing this change? Suggest two ways the village could adapt to these new conditions.

ANSWER Cause: these are signs of climate change, mainly caused by rising greenhouse gases from burning fossil fuels, along with local effects such as cutting down nearby trees, which reduces shade and rainfall. Two ways to adapt: (1) Harvest and store rainwater (build ponds, tanks and check-dams) and use water-saving irrigation so crops survive uncertain rains. (2) Plant more trees and grow drought-resistant or short-duration crops to cool the area, hold soil and reduce dependence on heavy rainfall. (Using clean energy and reducing waste also helps.)

11. If there were no atmosphere on the Earth, would it affect life, temperature, and water on the planet? Explain.

ANSWER Yes, it would seriously affect all three. Life: there would be no oxygen to breathe and no ozone layer, so harmful UV rays and space particles would reach the surface — most life could not survive. Temperature: with no atmosphere there would be no greenhouse effect, so the Earth would lose its heat to space and become extremely cold (and scorching where the Sun shines directly), with huge swings between day and night. Water: without atmospheric pressure and warmth, liquid water could not remain stable on the surface — it would freeze or evaporate away, so the oceans and rivers as we know them could not exist.

12. Discuss five examples of vegetative propagation.

ANSWER Vegetative propagation is asexual reproduction in plants from a part of the plant (leaf, stem or root). Five examples: (1) Potato — new plants grow from the ‘eyes’ (buds) of the tuber. (2) Ginger — new shoots grow from buds on the underground stem (rhizome). (3) Money plant — a stem cutting placed in soil or water grows roots and forms a new plant. (4) Sugarcane — pieces of stem with nodes are planted and sprout into new plants. (5) Onion — new plants grow from the bulb; (other valid examples: bryophyllum from leaf buds, rose or hibiscus from stem cuttings, banyan and bamboo).

Common Misconceptions to Avoid

Watch out for these

  • Thinking the hottest planet is the closest one — Venus is hotter than Mercury because its thick carbon-dioxide atmosphere traps heat (greenhouse effect).
  • Believing the greenhouse effect is always bad — a mild greenhouse effect keeps Earth warm enough for liquid water; only excess greenhouse gases cause harmful global warming.
  • Confusing the planet’s greenhouse effect with a plant greenhouse — the planet’s effect works by gases absorbing radiation, not just by trapping warm air behind glass.
  • Saying the habitable zone depends only on distance — size, atmosphere, ozone layer and magnetic field also make Earth habitable.
  • Mixing up the four spheres — geosphere (solid), hydrosphere (water), atmosphere (air), biosphere (life).
  • Thinking asexual reproduction produces variation — it gives near-identical copies; variation comes mainly from sexual reproduction.

Extra Practice Questions

Very Short Answer Type Questions

Q1. What is the other name for the habitable zone?

ANSWERThe Goldilocks zone.

Q2. Name the layer of the atmosphere that blocks harmful UV rays.

ANSWERThe ozone layer.

Q3. What are the three challenges together called the “triple planetary crisis”?

ANSWERClimate change, biodiversity loss and pollution.

Short Answer Type Questions

Q1. Why is liquid water important for Earth being a unique planet?

ANSWERAs far as we know, liquid water is essential for life to develop and survive. Earth lies at just the right distance from the Sun (the habitable zone), so water stays mostly liquid instead of freezing or evaporating — this is a key reason Earth can support life and looks blue from space.

Q2. Name the four spheres of the Earth system and what each consists of.

ANSWERThe atmosphere (air), hydrosphere (water), geosphere (the solid part — rocks, soil and minerals) and biosphere (all living things and their habitats). They interact and together sustain life on Earth.

Long Answer Type Question

Q1. Explain the main factors that make the Earth suitable for life to exist.

ANSWER Position: Earth lies in the habitable (Goldilocks) zone, at the right distance from the Sun for water to stay liquid; its nearly circular orbit keeps temperatures steady through the year. Size: Earth is large enough for its gravity to hold an atmosphere, but not so large that gravity would crush living things. Atmosphere and ozone: the atmosphere supplies oxygen for respiration and gives a mild greenhouse effect that keeps the planet warm; the ozone layer blocks harmful UV rays. Magnetic field: produced by molten iron in the core, it deflects cosmic rays and the solar wind, protecting the atmosphere and life. Together these factors allow liquid water and life to thrive.

MCQs & Assertion–Reason

1. The range of distances from a star where water can stay liquid is called the:

(a) ozone zone    (b) habitable (Goldilocks) zone    (c) magnetic zone    (d) greenhouse zone

2. Earth is called the “Blue Planet” mainly because:

(a) the sky looks blue    (b) it is cold    (c) most of its surface is covered with water    (d) it has a blue core

3. The hottest planet in the solar system is Venus because:

(a) it is closest to the Sun    (b) its thick atmosphere traps heat    (c) it has no atmosphere    (d) it has a strong magnetic field

4. The solid part of the Earth — rocks, soil and minerals — is called the:

(a) hydrosphere    (b) atmosphere    (c) geosphere    (d) biosphere

5. The Earth’s magnetic field protects us by deflecting:

(a) sunlight    (b) rainwater    (c) cosmic rays and the solar wind    (d) clouds

6. The ozone layer is important because it:

(a) provides oxygen to breathe    (b) blocks harmful ultraviolet rays    (c) makes rain    (d) creates gravity

7. Growing a new plant from a stem cutting of money plant is an example of:

(a) sexual reproduction    (b) pollination    (c) vegetative propagation    (d) fertilisation

8. In flowering plants, the male gametes are present in the:

(a) ovule    (b) pollen grains (anther)    (c) root    (d) fruit

9. The triple planetary crisis includes climate change, pollution and:

(a) earthquakes    (b) biodiversity loss    (c) volcanoes    (d) tides

10. On Mars, compared with Earth, the atmosphere is:

(a) much thicker    (b) about 100 times thinner    (c) exactly the same    (d) made mostly of oxygen

Answer key: 1-(b), 2-(c), 3-(b), 4-(c), 5-(c), 6-(b), 7-(c), 8-(b), 9-(b), 10-(b).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Earth lies in the habitable zone of the Sun.

Reason: At Earth’s distance from the Sun, the temperature allows water to remain in liquid form.

A-R 2. Assertion: Venus is hotter than Mercury even though Mercury is closer to the Sun.

Reason: Venus has a thick carbon-dioxide atmosphere that traps heat through the greenhouse effect.

A-R 3. Assertion: A very small planet (with the same density) would lose its atmosphere.

Reason: A smaller planet has stronger gravity that pulls the atmosphere inward.

A-R 4. Assertion: Asexual reproduction produces offspring with great variation from the parent.

Reason: In asexual reproduction a single parent produces exact copies of itself.

A-R 5. Assertion: The Earth’s magnetic field helps protect life on the planet.

Reason: It deflects harmful cosmic rays and the solar wind away from the Earth.

Answer key: 1-(A), 2-(A), 3-(C), 4-(D), 5-(A).

Quick Revision Summary

  • Earth is a unique planet because it supports life; it lies in the habitable (Goldilocks) zone where water stays liquid.
  • Its nearly circular orbit keeps temperatures steady; its right size lets gravity hold the atmosphere without crushing life.
  • The ozone layer blocks harmful UV rays; the magnetic field shields Earth from cosmic rays and the solar wind.
  • The atmosphere, hydrosphere, geosphere and biosphere interact and together sustain life.
  • Reproduction ensures the continuity of life: asexual (identical copies) and sexual (variation from two parents).
  • Climate change, biodiversity loss and pollution form the triple planetary crisis; balance must be protected.

Real-life Applications

Understanding Earth’s habitable conditions guides real choices: rainwater harvesting and tree planting help villages cope with rising temperatures and uncertain rains; using clean energy like solar and wind cuts greenhouse gases; reusing, repairing and recycling reduce pollution and waste. Knowing about the ozone layer led the world to the Montreal Protocol to phase out CFCs, while the Paris Agreement targets limiting global warming. Space missions like India’s Mangalyaan study whether other planets could ever support life.

How to score full marks in this chapter

Learn the four factors that make Earth habitable (position, size, ozone layer, magnetic field) and the four spheres with one line each. Remember why Venus is the hottest planet (greenhouse effect, not distance). For reproduction questions, clearly contrast asexual (one parent, identical) with sexual (two parents, gametes, variation), and keep five vegetative-propagation examples ready (potato, ginger, money plant, sugarcane, onion).

Frequently Asked Questions

What is Class 8 Science Curiosity Chapter 13 about?

It explains why Earth is a unique, life-sustaining planet — its position in the habitable (Goldilocks) zone, its right size and atmosphere, the ozone layer and magnetic field, how its four spheres sustain life, how reproduction continues life, and the threats of the triple planetary crisis.

What is the habitable zone or Goldilocks zone?

It is the range of distances from a star where the temperature is just right for water to stay liquid — neither too hot (so it boils away) nor too cold (so it freezes). Earth lies in this zone around the Sun.

How many questions are in the “Keep the curiosity alive” exercise of Chapter 13?

There are 12 questions, all solved on this page along with the “Probe and ponder” prompts and the activity.

Are these Class 8 Science Curiosity Chapter 13 solutions free?

Yes. All solutions are free and follow the official NCERT Curiosity textbook for 2026–27.

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