---
title: "NCERT Solutions Class 8 Science Our Home: Earth, a Unique Life Sustaining Planet"
url: https://www.swavid.com/science/class/8/chapter/our-home-earth-a-unique-life-sustaining-planet/ncert-solutions
dateModified: 2026-10-07T16:18:43+00:00
---

# NCERT Solutions Class 8 Science Our Home: Earth, a Unique Life Sustaining Planet

This chapter explores the unique conditions that make Earth a life-sustaining planet, covering Earth's position, atmosphere, magnetic field, and the fundamental processes of life and reproduction. It prompts students to analyze environmental challenges and planetary science concepts.

Free PDF (10 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-8/swavid-ncert-solutions-class-8-science-chapter-13-our-home-earth-a-unique-life-sustaining-planet-2629b86caf.pdf

## Probe and ponder

### Question z

*3 marks · Short answer*

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

**Solution**

1. Without life, Earth would look barren and lifeless, resembling rocky planets like Mars or Venus.
2. There would be no green forests, grasslands, blue oceans filled with aquatic life, or cities.
3. Only geological features like rocks, mountains, deserts, and water bodies would exist without any living organisms.

**Answer:** Without any life, Earth would be a barren planet with only rocks, mountains, and water bodies, lacking any green plants or animals.

> Common mistake: Describing Earth as completely devoid of water or atmosphere instead of focusing only on the absence of living forms.

### Question z

*3 marks · Short answer*

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

**Solution**

1. Life on Earth continues because of the delicate balance and interactions between living and non-living things in natural systems.
2. Reproduction ensures the continuity of life by passing on genetic instructions and allowing organisms to adapt to changes.
3. The presence of key resources like air, water, sunlight, and a protective atmosphere and magnetic field allows life to thrive.

**Answer:** Life keeps going due to the balance among natural resources, protective planetary conditions like the atmosphere and magnetic field, and reproduction.

> Common mistake: Forgetting to mention reproduction and adaptation as key factors in the survival of life over billions of years.

### Question z

*3 marks · Short answer*

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

**Solution**

1. Dogs are mammals in which the development of the zygote into an embryo takes place inside the mother's body, receiving food and oxygen directly from her.
2. Hens are birds that lay fertilised eggs with stored food where the embryo develops outside the body during hatching.
3. Due to their different internal reproductive strategies and evolutionary paths, dogs give birth to live young ones while hens lay eggs.

**Answer:** Dogs are mammals whose embryos develop inside the body, whereas hens are birds that lay eggs containing all the necessary food for the developing embryo.

> Common mistake: Confusing internal development in mammals with the egg-laying strategy of birds.

### Question z

*3 marks · Short answer*

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

**Solution**

1. Plants cannot start growing on Mars simply by bringing soil and water because Mars has extreme temperatures and a very thin atmosphere.
2. The Martian atmosphere is 100 times thinner than Earth's and lacks sufficient protective layers against harmful radiation.
3. For plants to grow, Mars would also need suitable temperatures, pressure, air composition, and protection from solar radiation.

**Answer:** No, plants could not grow just by adding soil and water because Mars lacks a thick atmosphere, suitable temperatures, and protection from radiation.

> Common mistake: Assuming water and soil alone are sufficient for plant growth without considering atmospheric conditions and temperature.

## Keep the curiosity alive

### Question 1

*1 mark · MCQ*

What is one major reason Mars cannot currently support life like Earth?

- It has too many volcanoes.
- It is too close to the Sun.
- It lacks a thick atmosphere and liquid water.
- Its magnetic field is too strong.

**Solution**

1. Mars lies at the edge of the Sun's habitable zone and lacks a thick atmosphere and liquid water, which are essential for life.
2. Option (i) and (iv) are incorrect statements about Mars, and option (ii) is false because Venus is closer.

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

> Common mistake: Confusing Mars with Venus regarding temperature or atmosphere thickness.

### Question 2

*1 mark · MCQ*

Which of these is an example of geodiversity?

- Variety of bird chirping in a forest.
- Different landforms like mountains, valleys, and deserts.
- Changing weather during monsoons.
- Number of different types of fish in a pond.

**Solution**

1. Geodiversity refers to the variety of non-living parts of nature such as different landforms, rocks, and soils.
2. Option (ii) correctly gives different landforms like mountains, valleys, and deserts as examples.

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

> Common mistake: Confusing geodiversity with biodiversity which relates to living organisms.

### Question 3

*1 mark · MCQ*

If the Earth were smaller with the same density, what might happen to its atmosphere?

- It would become thicker and hotter.
- It would escape into space due to weaker gravity.
- It would become frozen.
- It would cause stronger winds.

**Solution**

1. If Earth were much smaller with the same average density, its gravity would be too weak to hold onto the gases in the atmosphere.
2. Therefore, the atmospheric gases would escape into space.

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

> Common mistake: Assuming a smaller planet would retain its atmosphere easily.

### Question 4

*1 mark · MCQ*

In sexual reproduction, why are offspring different from their parents?

- They grow in different climates.
- They eat different food.
- They acquire new instructions after birth.
- They get mixed instructions (genes) from both parents.

**Solution**

1. In sexual reproduction, offspring receive genetic instructions from both parents.
2. The mixing of genes from two parents creates unique combinations, making offspring different from their parents.

**Answer:** (iv) They get mixed instructions (genes) from both parents.

> Common mistake: Thinking that offspring are exact copies of one parent as in asexual reproduction.

### Question 5

*3 marks · Short answer*

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?

**Solution**

1. The seeds likely arrived carried by birds or wind and got deposited in the cracks of the wall.
2. Rainwater during the monsoon provided the necessary moisture for the seeds to germinate.
3. The seeds used stored nutrients to grow roots and shoots, utilizing water, air, and trapped soil in the cracks.

**Answer:** Seeds were brought by wind or birds and germinated due to monsoon rainwater and trapped soil.

> Common mistake: Forgetting to explain how seeds reach high walls.

### Question 6

*5 marks · Long answer*

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?

**Solution**

1. Cutting down a forest reduces the number of trees that absorb carbon dioxide, leading to increased greenhouse gases and local climate warming.
2. Loss of habitats destroys plant and animal species, leading to a sharp decline in local biodiversity.
3. Without vegetation, rainwater runs off rapidly instead of seeping into the ground, reducing groundwater levels and depleting water availability.
4. Soil erosion from cleared land washes soil and pollutants into nearby water bodies, degrading water quality.
5. Diagram: Not required for this question.

**Answer:** Deforestation causes global warming, loss of biodiversity, reduced groundwater availability, and degraded water quality.

> Common mistake: Failing to connect deforestation with water table depletion and soil runoff.

### Question 7

*5 marks · Long answer*

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?

**Solution**

1. While natural climate changes have occurred in Earth's history, today's global warming is primarily driven by human activities like burning fossil fuels.
2. Burning fossil fuels releases extra carbon dioxide and other greenhouse gases that have been locked underground for millions of years.
3. The Earth's natural systems cannot absorb this massive surge of carbon fast enough, leading to a rapid buildup of heat in the atmosphere.
4. This enhanced greenhouse effect causes long-term changes in temperature, rainfall, and weather patterns known as climate change.
5. Unlike past slow changes, current global warming threatens the delicate balance required for human survival and biodiversity across the planet.

**Answer:** Today's global warming is happening at an unprecedented rate due to human activities like burning fossil fuels, releasing extra carbon that natural systems cannot absorb quickly enough.

> Common mistake: Ignoring the role of human fossil fuel burning and treating modern global warming as purely natural.

### Question 8

*3 marks · Short answer*

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

**Solution**

1. Earth's magnetic field acts as a protective shield that pushes harmful high-energy particles from space, such as cosmic rays and solar wind, away from the planet.
2. Without this magnetic field, these high-energy particles would constantly bombard the Earth and damage its atmosphere.
3. This damage would reduce the ozone layer, letting in more harmful ultraviolet rays that can severely affect and destroy living cells.

**Answer:** If Earth's magnetic field disappeared, harmful cosmic rays and solar wind would damage the atmosphere and deplete the ozone layer, exposing life to dangerous ultraviolet rays.

> Common mistake: Stating that the magnetic field protects us from gravity instead of high-energy particles from space.

### Question 9

*5 marks · Long answer*

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?

**Solution**

1. To support human life on Mars, we would need to recreate a breathable atmosphere with sufficient oxygen, liquid water sources, and a protective shield against harmful solar radiation.
2. We would also need to establish controlled temperature conditions and fertile soil containing nutrients for growing crops.
3. Among these requirements, creating a stable and breathable atmosphere of the right thickness is the hardest to replicate.
4. This is because Mars has very weak gravity compared to Earth, making it extremely difficult to hold onto a thick layer of gases without them escaping into space.

**Answer:** Three essential things to recreate are a breathable atmosphere, liquid water, and radiation shielding, with creating a thick atmosphere being the hardest due to Mars's weak gravity.

> Common mistake: Forgetting that Mars has lower gravity which prevents it from naturally retaining a thick atmosphere.

### Question 10

*3 marks · Short answer*

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.

**Solution**

1. The increasing temperature and unpredictable rainfall in the village are likely caused by climate change and global warming resulting from increased greenhouse gas emissions and environmental degradation.
2. To adapt to these new conditions, the village could adopt sustainable farming practices and water management techniques like rainwater harvesting.
3. They could also plant more trees and increase green cover to help regulate local temperatures and improve soil moisture.

**Answer:** The changes are likely due to climate change, and the village can adapt by implementing rainwater harvesting and adopting sustainable farming practices.

> Common mistake: Confusing weather adaptation strategies with causes of global warming.

### Question 11

*3 marks · Short answer*

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

**Solution**

1. Without an atmosphere, Earth would lose heat to space rapidly through radiation, making the planet extremely cold and causing all liquid water to freeze.
2. The greenhouse effect provided by atmospheric gases keeps the temperature just right for water to remain in liquid form, which is essential for life.
3. An atmosphere is also necessary to provide oxygen for respiration and protect living organisms from harmful solar radiation.

**Answer:** Without an atmosphere, Earth would become extremely cold, causing all liquid water to freeze and making it impossible for most life forms to survive.

> Common mistake: Stating that temperature would rise without an atmosphere, ignoring the heat-trapping greenhouse effect.

### Question 12

*3 marks · Short answer*

Discuss five examples of vegetative propagation.

**Solution**

1. Vegetative propagation is a type of asexual reproduction where new plants grow from parts of the parent plant such as stems, roots, or leaves.
2. Five examples include growing a new money plant from a stem cutting, potato plants from the 'eyes' of a sprouted potato, and new ginger plants from a piece of underground stem.
3. Other examples include growing new plants from the leaves of Bryophyllum and propagating sugarcane or roses using stem cuttings.

**Answer:** Five examples of vegetative propagation are growing new plants from money plant stem cuttings, potato 'eyes', ginger pieces, Bryophyllum leaves, and rose stem cuttings.

> Common mistake: Listing examples of plants grown from seeds instead of vegetative parts like stems, roots, or leaves.

## Discover, design, and debate

### Question z

*3 marks · Short answer*

Design an 'Earth Survival Kit'. Imagine you’re building a tiny model of Earth for another planet. What must it have to support life, and why?

**Solution**

1. It must have a habitable distance from its star to maintain liquid water.
2. It needs the right size and gravity to support a protective atmosphere and ozone layer.
3. It requires a magnetic field to shield against harmful cosmic rays and solar wind.

**Answer:** An Earth Survival Kit must include the correct distance from a star for liquid water, a suitable size for an atmosphere, and a magnetic field for protection.

> Common mistake: Forgetting to mention non-living factors like the magnetic field or atmosphere.

### Question z

*3 marks · Short answer*

India is planning for a challenging lunar mission, Chandrayaan-4, which will bring back samples of soil from the Moon. If the Moon had water, could plants grow in that soil? Think of some experiment that could help you explore whether plant growth is possible on the Moon.

**Solution**

1. Even if the lunar soil contained water, plants might still not grow because soil and water alone are not enough; plants also need appropriate nutrients, the right temperature, air containing carbon dioxide, and proper atmospheric pressure.
2. To explore whether plant growth is possible in lunar soil, an experiment can be designed by taking samples of the lunar soil and ordinary Earth soil in two separate pots under controlled conditions.
3. We can plant identical seeds in both pots, providing them with equal amounts of water, air, and sunlight, and then observe and compare their germination, root development, and overall growth over several weeks.

**Answer:** Plants need proper nutrients, temperature, and atmosphere along with soil and water; an experiment comparing plant growth in lunar soil versus Earth soil under controlled conditions can test its feasibility.

> Common mistake: Assuming that the presence of soil and water is alone sufficient for plant growth without considering nutrients, air, and environmental conditions.

### Question z

*3 marks · Short answer*

Flowers are often brightly coloured and have a pleasant smell. How do you think these features help the plant reproduce?

**Solution**

1. Bright colours and pleasant smells attract insects, birds, and other animals to the flower.
2. As these animals visit the flowers, pollen grains get attached to their bodies and are carried to other flowers.
3. This process of pollination leads to fertilisation and seed formation, helping the plant reproduce.

**Answer:** Bright colours and smells attract pollinators like insects, which transfer pollen between flowers to enable pollination and reproduction.

> Common mistake: Confusing pollination with seed dispersal.

### Question z

*3 marks · Short answer*

Why do animals like fish and frogs lay hundreds or even thousands of eggs at a time, while other animals lay only a few? What might be the advantages and disadvantages of laying so many eggs?

**Solution**

1. Animals like fish and frogs release eggs in water where external fertilisation takes place with no parental care.
2. The advantage of laying hundreds of eggs is that it increases the chances of at least some offspring surviving predators and harsh conditions.
3. The disadvantage is that many eggs and young ones are eaten or destroyed, requiring massive energy to produce.

**Answer:** Laying many eggs increases survival chances in unprotected aquatic environments, but requires high energy and suffers high predation rates.

> Common mistake: Failing to mention external fertilisation and lack of parental care in aquatic animals.

### Question z

*3 marks · Short answer*

Birds like sparrows build nests and care for their eggs and chicks, while reptiles like snakes usually lay their eggs and leave them without protection. How might this difference in parental care affect the chances of survival for the young ones in each case?

**Solution**

1. Birds like sparrows build nests and protect their eggs and chicks from predators and harsh weather.
2. Reptiles like snakes usually leave their eggs without protection, exposing them to environmental dangers and predators.
3. As a result, parental care greatly increases the survival chances of young birds compared to young reptiles, which must survive on their own from birth.

**Answer:** Active parental care in birds protects the young and increases their survival rate, whereas unprotected reptile eggs face much higher risks of being eaten or destroyed.

> Common mistake: Assuming all egg-laying animals care for their young equally.

## Frequently asked questions

### How many total questions are there in Class 8 Science Chapter 13 Our Home Earth a Unique Life Sustaining Planet?

This chapter in the new NCERT book for the 2026-27 session contains a total of 21 questions across three sections. There are 4 questions in Probe and ponder, 12 in Keep the curiosity alive, and 5 in Discover, design, and debate. SwaVid provides complete step-by-step solutions and a free PDF for all these questions on this page only.

### What topics do the exercise questions cover in this Class 8 Science chapter?

The questions cover important concepts such as the habitability of Mars, Earth's magnetic field, climate change impacts, deforestation, geodiversity, and animal and plant reproduction strategies. They also explore the specific requirements that make Earth a unique life-sustaining planet. SwaVid's free PDF on this page offers detailed explanations for every single topic.

### Which question types are the most challenging in this chapter and how should we approach them?

The long answer and multi-part analytical questions in the Keep the curiosity alive section can be somewhat tricky because they link human impact to global climate change and Earth's atmosphere. You should approach them by breaking down each scientific concept logically and structuring your points clearly. SwaVid helps you master these difficult questions with easy-to-understand solutions available in the free PDF on this page.

### How should I write my answers to score full marks in Class 8 Science exams?

To score full marks, write your answers in clear points using correct scientific terminology related to ecosystems, atmospheric roles, and biological reproduction. Always relate your explanation back to the core principles discussed in the chapter. You can refer to SwaVid's expert-crafted step-by-step solutions on this page to learn the right answer-writing format.

### Is a free PDF available for these NCERT solutions?

Yes, a comprehensive free PDF containing accurate answers for all textbook exercises is provided right here on this SwaVid page. You can easily download it to revise the chapter offline for your 2026-27 session exams.

## Related pages

- [Class 8 Science chapters](https://www.swavid.com/science/class/8)

Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student