Our Home Earth A Unique Life Sustaining Planet
Earth is, as far as we know, the only planet that supports life. This Class 8 Curiosity chapter explores what makes our home so special — its atmosphere, liquid water, suitable temperature and protective layers — and looks at the Earth's spheres, its natural resources, and why we must protect this unique life-sustaining planet.
Learning objectives
- Explain the conditions that make Earth suitable for life.
- Describe the atmosphere, hydrosphere, lithosphere and biosphere.
- Classify natural resources.
- Discuss threats to the Earth and ways to protect it.
Key concepts
Why Earth supports life
Earth lies at the right distance from the Sun, so it is neither too hot nor too cold, allowing water to stay liquid. It has an atmosphere rich in the oxygen living things need, and an ozone layer that shields us from harmful rays. These conditions together make life possible — a combination not found on other planets we know.
The spheres of the Earth
The Earth can be described in four overlapping parts. The atmosphere is the blanket of air around it; the hydrosphere is all its water — oceans, rivers, lakes and ice; the lithosphere is the solid land and rocky outer layer; and the biosphere is the zone where living things exist, where the other three spheres meet.
Natural resources
The materials nature provides for our use are natural resources. Renewable resources, like sunlight, wind, water and forests, can be replaced within a reasonable time, while non-renewable resources, like coal, petroleum and minerals, exist in limited amounts and take ages to form. Wise use makes them last.
Protecting our planet
Human activities can harm the Earth through air, water and land pollution, deforestation and overuse of resources. We can protect it by reducing, reusing and recycling, conserving water and energy, planting trees, and preventing pollution — caring for the only home we have.
Key definitions
- Atmosphere
- The layer of air surrounding the Earth.
- Hydrosphere
- All the water on the Earth — oceans, rivers, lakes and ice.
- Biosphere
- The zone of the Earth where living things exist.
- Renewable resource
- A natural resource that can be replaced within a reasonable time, like sunlight or forests.
Solved examples
Q1. Name two conditions that make Earth suitable for life.
Solution: A suitable temperature for liquid water and an atmosphere with oxygen (also the protective ozone layer).
Q2. Classify: (a) coal, (b) sunlight.
Solution: (a) coal — non-renewable; (b) sunlight — renewable.
Q3. To which sphere do oceans and rivers belong?
Solution: The hydrosphere — all the Earth's water.
Common mistakes to avoid
- Thinking other known planets also support life like Earth does.
- Confusing the hydrosphere (water) with the atmosphere (air).
- Calling coal or petroleum renewable — they are non-renewable.
- Believing resources are unlimited and need no conservation.
Our Home Earth A Unique Life Sustaining Planet — MCQ Quiz
10 questions with instant feedback. Use number keys 1–4 to answer.
The layer of air around the Earth is the:
Practice questions
Short answer
Why is Earth able to support life?
It has a suitable temperature for liquid water, an oxygen-rich atmosphere and a protective ozone layer.
Name the four spheres of the Earth.
Atmosphere, hydrosphere, lithosphere and biosphere.
Give one renewable and one non-renewable resource.
Renewable: sunlight (or wind/forests). Non-renewable: coal (or petroleum).
Long answer
Explain why the Earth is a unique life-sustaining planet.
Earth is special because several conditions for life occur together. It lies at the right distance from the Sun, so it is neither too hot nor too cold and water can remain liquid — vital for living things. Its atmosphere contains oxygen for breathing and carbon dioxide for plants, and the ozone layer high above blocks harmful rays from the Sun. The presence of liquid water, a breathable atmosphere and a suitable temperature, together with soil and nutrients, makes Earth able to support life — a combination not found on the other planets we know.
Describe the four spheres of the Earth and how they support the biosphere.
The atmosphere is the layer of air providing oxygen, carbon dioxide and protection; the hydrosphere is all the water in oceans, rivers, lakes and ice; the lithosphere is the solid land and rocky outer layer that holds soil and minerals. The biosphere is the thin zone where these three meet and where all living things exist — plants rooted in the lithosphere, drawing water from the hydrosphere and gases from the atmosphere. Life depends on the smooth interaction of all four spheres.
HOTS (Higher Order Thinking)
Why is liquid water so important in making Earth habitable, compared with a planet that has only ice or vapour?
Living things need liquid water for their life processes; a planet too cold has only ice and one too hot has only vapour, so only Earth's suitable temperature keeps water liquid and life possible.
How does planting more trees help protect several spheres at once?
Trees release oxygen and absorb carbon dioxide (atmosphere), hold soil and water (lithosphere and hydrosphere) and provide habitats (biosphere), so they benefit the whole Earth system.
Quick revision
Revision notes
- Earth supports life: right distance from Sun, liquid water, oxygen, ozone layer.
- Four spheres: atmosphere (air), hydrosphere (water), lithosphere (land), biosphere (life).
- Resources: renewable (sunlight, wind, forests) vs non-renewable (coal, petroleum).
- Protect Earth: reduce, reuse, recycle; conserve; prevent pollution; plant trees.
Key takeaways
- Several conditions together make Earth uniquely habitable.
- The four spheres interact to support life.
- Non-renewable resources are limited and must be conserved.
Frequently asked questions
What makes Earth suitable for life?
Its distance from the Sun, liquid water, an oxygen-rich atmosphere and the protective ozone layer.
What are the Earth's four spheres?
Atmosphere, hydrosphere, lithosphere and biosphere.
What is the difference between renewable and non-renewable resources?
Renewable resources can be replenished in a reasonable time; non-renewable ones are limited and take ages to form.