Class 8 Science

Chapter 13 Solutions — Our Home: Earth, a Unique Life Sustaining Planet

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Solutions

Overview

Step-by-step NCERT solutions for Our Home: Earth, a Unique Life Sustaining Planet (Chapter 13, NCERT Class 8 Science) — every question and answer worked out in full, not just the final result. You can also read the Our Home: Earth, a Unique Life Sustaining Planet textbook chapter.

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What these solutions cover

All 12 questions in Our Home: Earth, a Unique Life Sustaining Planet are solved in the PDF. Here's what's inside, exercise by exercise:

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.
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.
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.
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.
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?
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?
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?
Imagine Earth's magnetic field suddenly disappeared. What kinds of problems could arise for life on Earth? Explain.
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?
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.
If there were no atmosphere on the Earth, would it affect life, temperature, and water on the planet? Explain.
Discuss five examples of vegetative propagation.

Sample

Worked examples

3 questions from Our Home: Earth, a Unique Life Sustaining Planet, solved step by step.

Keep the Curiosity Alive

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.

Evaluating each option against what we know about Mars:

(i) Too many volcanoes — volcanoes are present on Mars, but they are not a major barrier to life as we know it. INCORRECT.

(ii) Too close to the Sun — Mars is farther from the Sun than Earth, lying at the outer edge of the habitable zone. INCORRECT.

(iii) Lacks a thick atmosphere and liquid water — Mars's atmosphere is about 100 times thinner than Earth's, and no liquid water exists on its surface today. Without a thick atmosphere, temperatures are extreme and water cannot remain liquid, making life as we know it impossible. CORRECT.

(iv) Magnetic field too strong — Mars's magnetic field is extremely weak, not strong. INCORRECT.

Therefore, option (iii) is correct.

Answer: (iii) It lacks a thick atmosphere and liquid water.

Keep the Curiosity Alive

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.

Geodiversity refers to the variety of landforms, rocks, soils, and the processes that shape them on Earth.

Evaluating each option:

(i) Variety of bird chirping — this is diversity of animal behaviour, not of landforms or non-living geological features. INCORRECT.

(ii) Different landforms like mountains, valleys, and deserts — these are non-living geographical features; their variety is exactly what geodiversity describes. CORRECT.

(iii) Changing weather during monsoons — weather is an atmospheric phenomenon, not a geological one. INCORRECT.

(iv) Number of different types of fish in a pond — this is biodiversity (variety of living organisms), not geodiversity. INCORRECT.

Therefore, option (ii) is correct.

Answer: (ii) Different landforms like mountains, valleys, and deserts.

Keep the Curiosity Alive

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.

Gravity depends on the mass of a planet. If Earth were smaller but had the same density, its total mass would be less, so its gravitational pull would be weaker.

Evaluating each option:

(i) Thicker and hotter — weaker gravity cannot hold more gas; it would do the opposite. INCORRECT.

(ii) Escape into space due to weaker gravity — with weaker gravity, the planet would be unable to hold gas molecules against their natural tendency to fly off into space, just as Mars (with a much thinner atmosphere) demonstrates. CORRECT.

(iii) Become frozen — the temperature of the atmosphere depends mainly on distance from the Sun and greenhouse gases, not directly on the planet's size. INCORRECT.

(iv) Cause stronger winds — wind patterns are driven by temperature differences and rotation, not by the planet's size in this way. INCORRECT.

Therefore, option (ii) is correct.

Answer: (ii) It would escape into space due to weaker gravity.

All 12 questions in Our Home: Earth, a Unique Life Sustaining Planet are solved step by step in the Solutions PDF above.

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Chapter 13 Solutions — Our Home: Earth, a Unique Life Sustaining Planet

Overview

What these solutions cover

Keep the Curiosity Alive

Worked examples

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.

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.

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.

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