Most life exists in a very thin layer at Earth’s surface mainly because ______.

Gravity is weaker at the surface

Conditions for air, water and suitable temperatures occur there

False colour images are useful because they can ______.

Show features like vegetation or sediments clearly

Earth is often called the 'Blue Planet' because ______.

Its atmosphere is blue-coloured gas

Most of its surface is covered by water

Why is Venus hotter than Mercury?

Its thick CO₂ atmosphere traps heat (greenhouse effect)

Which statement about greenhouse effect on Earth is TRUE?

It traps some heat and helps keep Earth warm enough for liquid water

A greenhouse for plants warms mainly because ______.

It is a closed space that traps warmed air

Which factor MOST directly explains why Mercury is not the hottest planet?

It lacks a thick heat-trapping atmosphere

Earth can retain an atmosphere primarily because of its ______.

Appropriate gravity due to its size

If Earth were much smaller (same density), which is MOST likely?

Stronger gravity and thicker air

Gases would escape more easily into space

Ozone in the atmosphere is important because it ______.

Blocks harmful ultraviolet (UV) radiation

Which comparison is TRUE about atmospheres?

Mars has a thicker atmosphere than Earth

Mercury has no appreciable atmosphere

All rocky planets have identical air

Earth’s magnetic field helps life mainly by ______.

Deflecting harmful charged particles from space

Which ISRO mission successfully orbited Mars in 2013?

Mangalyaan (Mars Orbiter Mission)

Circular orbits of planets help by ______.

Keeping sunlight received more steady, moderating extremes

The immediate cause for auroras is interaction of atmospheric gases with ______.

Charged particles guided by Earth’s magnetic field

Water is vital in plants mainly because it ______.

Transports nutrients from roots to leaves

The biosphere includes ______.

All living beings and their habitats on land, water, and air

Soil nutrients such as nitrogen and potassium primarily come from ______.

Breakdown of rocks and organic matter

Which combination BEST illustrates Earth’s interdependence?

Plants release oxygen; animals use oxygen; decomposers recycle nutrients

Without an atmosphere, Earth would likely be ______.

Too cold due to rapid heat loss to space

Rainfall patterns influence ______.

Which plants and animals can live in a place

Geodiversity refers to ______.

Variety of landforms, rocks, and processes shaping them

Balance among land, air, water, and life is important primarily because ______.

It keeps conditions suitable for life

Genes are best described as ______.

Chemicals that cause earthquakes

Instructions inside cells for growth and function

Variations that aid survival can, over generations, lead to ______.

New traits or even new life forms

Asexual reproduction generally produces offspring that are ______.

Genetically identical to the parent

In sexual reproduction, offspring differ from parents mainly because ______.

They receive mixed genetic material from two gametes

In birds, development of the embryo occurs mainly ______.

After the egg is laid during hatching

A key difference between most mammals and birds is that mammals usually ______.

Develop embryos internally and give birth to young ones

NCERT Solutions Class 8 Science - Curiosity Chapter 13 – Our Home: Earth, a Unique Life Sustaining Planet

Name: Our Home: Earth, a Unique Life Sustaining Planet – Class 8 Science - Curiosity
Uploaded: 2026-05-31
Description: Earth is a unique planet that supports life due to its right distance from the Sun, atmosphere, water, and magnetic field. Life thrives through the balance of living and non-living things, but human actions like pollution and climate change threaten this delicate balance. Protecting Earth requires responsible actions from everyone.

Class 8 Science - Curiosity

Last Updated: 31 May 2026

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Chapter Introduction

Earth is a unique planet that supports life due to its right distance from the Sun, atmosphere, water, and magnetic field. Life thrives through the balance of living and non-living things, but human actions like pollution and climate change threaten this delicate balance. Protecting Earth requires responsible actions from everyone.

हिंदी में (Hindi)

पृथ्वी एक अनोखा ग्रह है जो जीवन को अपने सही सूर्य से दूरी, वायुमंडल, जल और चुंबकीय क्षेत्र के कारण सहारा देता है। जीवन जीवित और निर्जीव तत्वों के संतुलन पर निर्भर करता है, लेकिन प्रदूषण और जलवायु परिवर्तन इसे खतरे में डाल रहे हैं। पृथ्वी की रक्षा के लिए हम सभी की जिम्मेदारी जरूरी है।

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Important Points

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Practice MCQ Questions (60 questions)

Q1. Which layer of Earth hosts all known life?

Q2. If Earth were the size of an apple, the crust would be comparable to the apple’s ______.

Q3. The ISRO Earth mosaic image is called 'false colour' because it ______.

Q4. Satellite images can help detect all of the following EXCEPT:

Q5. Which statement best explains why Earth is extraordinary among planets we know?

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Tough Words (Glossary)

sustain

Meaning: to keep something going; to support and maintain

अर्थ: संचालित/बनाए रखना; सहारा देना

"Trees help sustain life by giving us oxygen."

unique

Meaning: one of a kind; unlike anything else

अर्थ: अद्वितीय; जो और किसी जैसा न हो

"Earth is unique because it supports life."

landscape

Meaning: the visible features of an area of land

अर्थ: परिदृश्य; भू-दृश्य

"Satellites capture the changing landscape of Earth."

mosaic

Meaning: a picture made by putting many small pieces together

अर्थ: जड़ाऊ चित्र; छोटे टुकड़ों से बनी तस्वीर

"The satellite made a mosaic of 3000 images."

false colour image

Meaning: an image where colors are changed to show special information

अर्थ: झूठे रंग की छवि; जानकारी दिखाने हेतु बदले रंग

"Scientists used a false colour image to study plants."

detect

Meaning: to notice or discover something

अर्थ: पता लगाना; खोज निकालना

"Satellites can detect oil spills in the ocean."

organism

Meaning: any living thing like a plant, animal, or microbe

अर्थ: जीव; कोई भी सजीव चीज

"Tiny organisms live deep in the ocean."

thrive

Meaning: to grow well and be healthy

अर्थ: फलना-फूलना; अच्छी तरह बढ़ना

"Life can thrive on Earth because of water and air."

crust

Meaning: the thin outer layer of the Earth

अर्थ: भूपर्पटी; पृथ्वी की बाहरी पतली परत

"All life lives on the Earth’s crust."

trench

Meaning: a deep, long narrow hole in the ground or ocean

अर्थ: गहरा खड्ड/खाई; समुद्री गर्त

"The deepest ocean trench is far below sea level."

atmosphere

Meaning: the layer of gases around a planet

अर्थ: वायुमंडल; ग्रह के चारों ओर गैसों की परत

"The atmosphere protects us from harmful rays."

satellite

Meaning: an object that orbits a planet; natural or man-made

अर्थ: उपग्रह; जो ग्रह की परिक्रमा करता है

"A weather satellite helps forecast storms."

habitable zone

Meaning: the region around a star where liquid water can exist

अर्थ: वासयोग्य क्षेत्र; जहाँ तरल जल संभव हो

"Earth lies in the Sun’s habitable zone."

greenhouse effect

Meaning: warming caused when gases trap heat

अर्थ: ग्रीनहाउस प्रभाव; गैसों द्वारा ऊष्मा फँसाकर गरम होना

"The greenhouse effect keeps Earth warm enough for life."

carbon dioxide

Meaning: a gas (CO₂) present in air that traps heat

अर्थ: कार्बन डाइऑक्साइड; एक गैस जो ऊष्मा रोकती है

"Too much carbon dioxide causes global warming."

radiation

Meaning: energy that travels as waves or particles

अर्थ: विकिरण; तरंगों/कणों के रूप में ऊर्जा

"Earth absorbs sunlight and gives off infrared radiation."

evaporate

Meaning: to change from liquid to gas

अर्थ: वाष्पित होना; द्रव से गैस बनना

"If Earth were closer to the Sun, water would evaporate."

freeze

Meaning: to become solid because of cold

अर्थ: जमना; ठंड से ठोस बनना

"Far from the Sun, water would freeze."

orbit

Meaning: the path an object follows around another object

अर्थ: कक्षा; किसी पिंड की परिक्रमा पथ

"Planets orbit the Sun in almost circular paths."

gravity

Meaning: a force that pulls objects toward each other

अर्थ: गुरुत्वाकर्षण; खींचने वाली शक्ति

"Earth’s gravity holds the atmosphere."

ozone layer

Meaning: a layer of ozone gas that blocks harmful UV rays

अर्थ: ओजोन परत; जो हानिकारक UV किरणों को रोकती है

"The ozone layer protects our skin from sunburn."

ultraviolet (UV) rays

Meaning: invisible rays from the Sun that can harm living things

अर्थ: अल्ट्रावायलेट किरणें; सूर्य की हानिकारक अदृश्य किरणें

"Too much UV rays can damage eyes and skin."

magnetic field

Meaning: the area around a magnet where it exerts force

अर्थ: चुंबकीय क्षेत्र; जहाँ चुंबक का प्रभाव रहता है

"Earth’s magnetic field deflects many harmful particles."

molten

Meaning: melted by heat (usually metal or rock)

अर्थ: पिघला हुआ; ऊष्मा से द्रव बना

"Movements of molten iron in the core create magnetism."

cosmic rays

Meaning: high‑energy particles coming from outer space

अर्थ: कॉस्मिक किरणें; अंतरिक्ष से आने वाले ऊर्जावान कण

"Cosmic rays constantly hit Earth’s atmosphere."

solar wind

Meaning: a stream of charged particles from the Sun

अर्थ: सौर पवन; सूर्य से आने वाले आवेशित कण

"The solar wind can disturb satellites."

shield

Meaning: to protect from harm; a protective cover

अर्थ: ढाल; सुरक्षा देना

"The magnetic field acts as a shield for Earth."

hydrosphere

Meaning: all the water on Earth (oceans, rivers, lakes, etc.)

अर्थ: जलमंडल; पृथ्वी पर मौजूद समस्त जल

"Oceans are the largest part of the hydrosphere."

geosphere

Meaning: the solid parts of Earth: rocks, soil, and landforms

अर्थ: स्थलमंडल/भू-मंडल; पृथ्वी का ठोस भाग

"Minerals in the geosphere support human life."

biosphere

Meaning: all regions of Earth where life exists

अर्थ: जीवमंडल; जहाँ जीवन पाया जाता है

"Forests are rich parts of the biosphere."

geodiversity

Meaning: variety of rocks, soils, and landforms on Earth

अर्थ: भू-विविधता; चट्टानों, मिट्टियों और स्थलाकृतियों की विविधता

"High geodiversity creates many habitats."

nutrient

Meaning: a substance that helps living things grow and stay healthy

अर्थ: पोषक तत्व; विकास के लिए आवश्यक पदार्थ

"Soil nutrients help crops grow well."

photosynthesis

Meaning: process by which plants make food using sunlight

अर्थ: प्रकाश संश्लेषण; सूर्य के प्रकाश से पौधों द्वारा भोजन बनाना

"Photosynthesis releases oxygen into the air."

respiration

Meaning: using oxygen to release energy from food

अर्थ: श्वसन; भोजन से ऊर्जा पाने हेतु ऑक्सीजन का प्रयोग

"Humans need oxygen for respiration."

balance (ecological)

Meaning: a stable condition where parts of nature support each other

अर्थ: संतुलन (पारिस्थितिक); प्रकृति का स्थिर संतुलन

"Cutting forests upsets ecological balance."

genetic material

Meaning: information in cells that controls how living things develop

अर्थ: आनुवंशिक सामग्री; कोशिका में विकास की जानकारी

"Genes are the genetic material passed to offspring."

gene

Meaning: a unit of heredity that carries instructions in DNA

अर्थ: जीन; वंशागति की इकाई

"Eye colour is decided by genes."

asexual reproduction

Meaning: reproduction with one parent producing identical offspring

अर्थ: अलैंगिक जनन; एक माता-पिता से समान संतान बनना

"Amoeba shows asexual reproduction by dividing in two."

vegetative propagation

Meaning: growing new plants from stems, roots, or leaves

अर्थ: वनस्पति प्रवर्धन; तना/जड़/पत्ती से नया पौधा उगाना

"Potato and ginger grow by vegetative propagation."

gamete

Meaning: a reproductive cell with half the genetic material

अर्थ: गैमेट/जनन कोशिका; आधी आनुवंशिक सामग्री वाली कोशिका

"Sperm and egg are human gametes."

fertilisation

Meaning: joining of male and female gametes

अर्थ: निषेचन; नर और मादा गैमेट का मिलन

"Fertilisation forms a zygote in plants and animals."

zygote

Meaning: the first cell formed after fertilisation

अर्थ: युग्मनज/ज़ाइगोट; निषेचन के बाद बनी पहली कोशिका

"The zygote grows into an embryo."

embryo

Meaning: an early stage of development of a baby plant or animal

अर्थ: भ्रूण; विकास का प्रारंभिक चरण

"A bird’s embryo develops inside the egg."

germination

Meaning: the process by which a seed begins to grow

अर्थ: अंकुरण; बीज का उगना शुरू होना

"Rain helps the germination of seeds."

biodiversity

Meaning: the variety of living things in an area

अर्थ: जैव विविधता; किसी क्षेत्र में जीवों की विविधता

"Protecting forests saves biodiversity."

fossil fuels

Meaning: energy sources like coal, oil, and gas formed from ancient life

अर्थ: जीवाश्म ईंधन; कोयला, तेल, गैस

"Burning fossil fuels releases greenhouse gases."

methane

Meaning: a powerful greenhouse gas (CH₄)

अर्थ: मीथेन; प्रबल ग्रीनहाउस गैस

"Methane from wetlands and cattle adds to warming."

global warming

Meaning: the rise in Earth’s average temperature

अर्थ: वैश्विक ऊष्मीकरण; पृथ्वी के औसत ताप का बढ़ना

"Global warming melts polar ice."

acid rain

Meaning: rain mixed with harmful acids from pollution

अर्थ: अम्ल वर्षा; प्रदूषण से बनी अम्लीय वर्षा

"Acid rain can damage crops and buildings."

renewable energy

Meaning: energy from sources that don’t run out quickly

अर्थ: नवीकरणीय ऊर्जा; जल्दी खत्म न होने वाले स्रोतों से ऊर्जा

"Solar power is a form of renewable energy."

sustainable

Meaning: able to continue without harming nature

अर्थ: टिकाऊ/स्थायी; प्रकृति को नुकसान पहुँचाए बिना चलने योग्य

"We must choose sustainable ways of living."

interdependent

Meaning: needing and affecting each other

अर्थ: परस्पर निर्भर; एक‑दूसरे पर आधारित

"Air, water, soil, and life are interdependent."

NCERT Solutions Class 8 Science - Curiosity Chapter 13 – Our Home: Earth, a Unique Life Sustaining Planet

Chapter Introduction

Watch Video Lecture

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Important Points

Practice MCQ Questions (60 questions)

Q1. Which layer of Earth hosts all known life?

Q2. If Earth were the size of an apple, the crust would be comparable to the apple’s ______.

Q3. The ISRO Earth mosaic image is called 'false colour' because it ______.

Q4. Satellite images can help detect all of the following EXCEPT:

Q5. Which statement best explains why Earth is extraordinary among planets we know?

Q6. Most life exists in a very thin layer at Earth’s surface mainly because ______.

Q7. Which natural resource is NOT directly provided by Earth’s crust?

Q8. Which Indian agency created a mosaic of ~3000 images of Earth?

Q9. False colour images are useful because they can ______.

Q10. Earth is often called the 'Blue Planet' because ______.

Q11. Which group lists the four inner rocky planets in order from the Sun?

Q12. Which planet is the hottest in our solar system?

Q13. Why is Venus hotter than Mercury?

Q14. The term 'habitable zone' refers to the region around a star where ______.

Q15. Which statement about greenhouse effect on Earth is TRUE?

Q16. A greenhouse for plants warms mainly because ______.

Q17. Which planet lies near the outer edge of the Sun’s habitable zone and shows past signs of liquid water?

Q18. Jupiter, Saturn, Uranus, Neptune are classified as ______.

Q19. All planets receive energy from ______.

Q20. Which factor MOST directly explains why Mercury is not the hottest planet?

Q21. Earth can retain an atmosphere primarily because of its ______.

Q22. If Earth were much smaller (same density), which is MOST likely?

Q23. Ozone in the atmosphere is important because it ______.

Q24. Which comparison is TRUE about atmospheres?

Q25. Earth’s magnetic field helps life mainly by ______.

Q26. High‑energy particles that originate from the Sun are called ______.

Q27. Which ISRO mission successfully orbited Mars in 2013?

Q28. Circular orbits of planets help by ______.

Q29. A key gas required for respiration by most life on Earth is ______.

Q30. The immediate cause for auroras is interaction of atmospheric gases with ______.

Q31. The hydrosphere includes ______.

Q32. Water is vital in plants mainly because it ______.

Q33. The geosphere refers to ______.

Q34. The biosphere includes ______.

Q35. Soil nutrients such as nitrogen and potassium primarily come from ______.

Q36. Which combination BEST illustrates Earth’s interdependence?

Q37. Without an atmosphere, Earth would likely be ______.

Q38. Rainfall patterns influence ______.

Q39. Geodiversity refers to ______.

Q40. Balance among land, air, water, and life is important primarily because ______.

Q41. Reproduction maintains life on Earth by ______.

Q42. Genes are best described as ______.

Q43. Variations that aid survival can, over generations, lead to ______.

Q44. Asexual reproduction generally produces offspring that are ______.

Q45. Which is an example of vegetative propagation?

Q46. In sexual reproduction, offspring differ from parents mainly because ______.

Q47. Pollination is the transfer of pollen from ______.

Q48. After fertilisation in flowering plants, the ovule becomes the ______.

Q49. In birds, development of the embryo occurs mainly ______.

Q50. A key difference between most mammals and birds is that mammals usually ______.

Q51. The 'triple planetary crisis' consists of climate change, biodiversity loss, and ______.

Q52. Burning fossil fuels adds extra CO₂ primarily because ______.

Q53. A likely effect of global warming is ______.

Q54. Biodiversity loss can disrupt ecosystems because ______.

Q55. Air pollution can lead to ______.

Q56. Which international agreement led to phasing down CFCs to protect the ozone layer?

Q57. The Paris Agreement aims to limit global warming to below ______.

Q58. A sustainable action individuals can take is to ______.

Q59. Protecting climate primarily requires ______.

Q60. Why are diverse ecosystems generally more resilient?