Earth is a life-sustaining planet because its air, water, temperature, gravity, and magnetic field support living systems. Life continues because Earth’s atmosphere, hydrosphere, geosphere, and biosphere interact in balance. Reproduction, adaptation, and natural systems help living beings survive through change.
Earth’s uniqueness becomes clearer when students compare it with planets that are too hot, too cold, too dry, or too thinly protected. Important Questions Class 8 Science Chapter 13 focus on habitable zone, greenhouse effect, atmosphere, ozone layer, magnetic field, liquid water, geosphere, hydrosphere, biosphere, reproduction, Mars, Venus, and triple planetary crisis. The CBSE 2026 chapter also explains why life survives through reproduction and variation. Students should revise this chapter through short answers, MCQs, reasoning questions, and NCERT-style application questions.
Key Takeaways
- Habitable Zone: Earth lies at a distance where water can remain liquid.
- Atmosphere: Earth’s gravity holds gases that support respiration and temperature balance.
- Magnetic Field: Earth’s magnetic field protects the planet from harmful space particles.
- Reproduction: Sexual and asexual reproduction maintain the continuity of life.
Important Questions Class 8 Science Chapter 13 Structure 2026
| Principle |
Application |
Unit |
| Earth’s Conditions |
Explain life support on Earth |
planet system |
| Reproduction |
Explain continuity and variation |
living beings |
| Climate Threats |
Explain pollution and global warming |
Earth system |
Important Questions Class 8 Science Chapter 13 With Answers
Important questions class 8 science chapter 13 help students revise why Earth supports life. These answers follow the NCERT Reprint 2026-27 chapter.
Q1. Why Is Earth Called A Unique Planet?
Earth is called a unique planet because it supports life. It has liquid water, suitable temperature, atmosphere, gravity, and a protective magnetic field.
Earth also has soil, minerals, sunlight, oxygen, and living systems. These conditions work together to sustain life.
Q2. Why Is Earth Called The Blue Planet?
Earth is called the Blue Planet because most of its surface is covered with water. It looks blue from space.
Oceans cover a large part of Earth. This water supports aquatic life, rainfall, farming, and human survival.
Q3. What Is The Earth’s Crust?
Earth’s crust is the thin outer layer where life exists. It includes land, soil, rocks, mountains, forests, and ocean floors.
The chapter compares the crust with apple skin. The comparison shows how thin the life-supporting layer is.
Q4. What Is The Habitable Zone?
The habitable zone is the region around a star where liquid water can exist. It is also called the Goldilocks zone.
Earth lies in this zone around the Sun. This allows water to remain mostly liquid.
Q5. Why Is Liquid Water Essential For Life?
Liquid water is essential because living organisms need it for life processes. It supports transport, digestion, hydration, and plant growth.
Plants use water for photosynthesis. Animals use water for body functions and temperature regulation.
Q6. What Makes Earth Suitable For Life?
Earth supports life because it has the right distance, size, atmosphere, water, ozone layer, and magnetic field. These factors work together.
Earth also has soil, minerals, sunlight, and balanced natural cycles. These support living beings.
Class 8 Science Chapter 13 Important Questions On Earth As A Unique Planet
Class 8 science chapter 13 important questions often ask why Earth differs from other planets. Students should connect Earth’s position, size, and atmosphere.
Q7. Why Is Earth’s Distance From The Sun Important?
Earth’s distance from the Sun keeps its temperature suitable for liquid water. This supports most known life forms.
If Earth were closer, water could evaporate. If Earth were farther, water could freeze.
Q8. Why Would Earth Become Too Hot If It Were Closer To The Sun?
Earth would become too hot because it would receive more solar heat. Liquid water could evaporate quickly.
Most plants, animals, and humans cannot survive without liquid water. Extreme heat would damage life systems.
Q9. Why Would Earth Become Too Cold If It Were Farther From The Sun?
Earth would become too cold because it would receive less solar heat. Water could freeze across the planet.
Frozen water cannot support most life processes. Only some microbes can survive in extreme frozen conditions.
Q10. Why Is Earth’s Size Important For Life?
Earth’s size gives it enough gravity to hold an atmosphere. This atmosphere supports breathing and temperature balance.
If Earth were much smaller, gases could escape into space. Mercury has no atmosphere.
Q11. What Would Happen If Earth Were Much Larger?
If Earth were much larger, gravity could become too strong for living bodies. Movement and body support would become difficult.
The chapter explains that very strong gravity could crush bones. Earth’s present size supports life comfortably.
Q12. Why Is Earth’s Orbit Important?
Earth’s nearly circular orbit keeps heat and sunlight fairly steady through the year. This prevents extreme yearly temperature swings.
Stable conditions help water, plants, animals, and humans survive. Earth receives a balanced amount of solar energy.
Our Home Earth A Unique Life Sustaining Planet Class 8 Questions And Answers
Our home earth a unique life sustaining planet class 8 questions and answers include Venus, Mars, greenhouse effect, ozone, and magnetic field. These answers build concept clarity.
Q13. Why Is Venus Hotter Than Mercury?
Venus is hotter than Mercury because its thick carbon dioxide atmosphere traps heat strongly. This creates an intense greenhouse effect.
Mercury is closer to the Sun but lacks a thick atmosphere. Venus keeps more heat trapped.
Q14. What Is The Greenhouse Effect?
The greenhouse effect is the trapping of heat by gases in a planet’s atmosphere. Carbon dioxide is one such gas.
On Earth, a mild greenhouse effect keeps the planet warm. On Venus, it makes the planet extremely hot.
Q15. How Is Earth’s Greenhouse Effect Useful?
Earth’s greenhouse effect helps maintain a suitable temperature for liquid water. It prevents Earth from losing too much heat.
Without an atmosphere, Earth would become too cold. A mild greenhouse effect supports life.
Q16. Why Can Mars Not Currently Support Life Like Earth?
Mars cannot currently support life like Earth because it lacks a thick atmosphere and stable liquid water. Its conditions remain harsh.
Mars may have had liquid water in the past. Scientists continue to study Mars for clues.
Q17. Why Does Mars Interest Scientists?
Mars interests scientists because it may have had liquid water and life-friendly conditions in the past. Space missions study its surface and atmosphere.
India’s Mangalyaan studied Mars from orbit. It helped scientists explore questions about Mars.
Q18. What Is The Ozone Layer?
The ozone layer is a protective layer in the atmosphere that blocks harmful ultraviolet rays. It contains ozone molecules.
Ozone is a three-atom form of oxygen. It protects living cells from UV damage.
Q19. Why Is Earth’s Magnetic Field Important?
Earth’s magnetic field protects the planet from harmful high-energy particles from space. It acts like a shield.
It deflects many cosmic rays and solar wind particles. This helps protect the atmosphere and life.
Class 8 Science Chapter 13 Extra Questions With Answers On Sustaining Life
Class 8 science chapter 13 extra questions with answers should cover atmosphere, hydrosphere, geosphere, and biosphere. These systems interact to keep Earth habitable.
Q20. What Is The Atmosphere?
The atmosphere is the layer of gases surrounding Earth. It contains oxygen, carbon dioxide, nitrogen, and other gases.
Oxygen supports respiration. Carbon dioxide supports photosynthesis and the greenhouse effect.
Q21. What Is The Hydrosphere?
The hydrosphere includes all water on Earth. It includes oceans, rivers, lakes, groundwater, ice, and water vapour.
Water supports plants, animals, microbes, farming, and weather. It also transports nutrients in living beings.
Q22. What Is The Geosphere?
The geosphere includes Earth’s solid parts, such as rocks, soil, landforms, and minerals. It supports ecosystems and human life.
Soil helps plants grow. Minerals provide materials like salt, coal, oil, iron, and copper.
Q23. What Is The Biosphere?
The biosphere includes all living beings and the places where they live. It includes life on land, in water, and in air.
Plants, animals, insects, microbes, and humans form part of the biosphere. They interact with other Earth systems.
Q24. What Is Geodiversity?
Geodiversity means the variety of landforms, rocks, soils, and processes that shape them. It helps create different habitats.
Mountains, valleys, deserts, rocks, and soils are examples. Different habitats support different life forms.
Q25. How Do Plants Help Sustain Life On Earth?
Plants sustain life by making food through photosynthesis and releasing oxygen. They also support food chains.
Plants use sunlight, carbon dioxide, and water. Animals depend on plants directly or indirectly.
Q26. How Do Decomposers Help Earth’s Life Systems?
Decomposers break down dead matter and return nutrients to soil. This helps plants grow again.
Bacteria and fungi act as decomposers. They support nutrient recycling in ecosystems.
Class 8 Science Chapter 13 Questions And Answers On Reproduction
Class 8 science chapter 13 questions and answers on reproduction explain continuity of life. Reproduction helps organisms continue and adapt.
Q27. Why Is Reproduction Essential For Life?
Reproduction is essential because it ensures the continuity of each kind of organism. Without reproduction, life forms would disappear.
Plants, animals, and microbes reproduce. This keeps populations going across generations.
Q28. What Are Genes?
Genes are instructions stored inside cells that guide how living beings develop. They pass from parents to offspring.
Genes help form body parts and traits. They explain why calves become cows and kittens become cats.
Q29. Why Do Offspring Resemble Their Parents?
Offspring resemble their parents because they inherit genes from them. These genes carry development instructions.
A calf resembles a cow because it receives cow genetic instructions. A chick develops from bird genetic instructions.
Q30. Why Are Offspring Not Exactly Like Their Parents In Sexual Reproduction?
Offspring differ because they receive mixed genetic instructions from two parents. This creates variation.
A child may resemble both parents in different ways. Each offspring gets a unique gene combination.
Q31. What Is Asexual Reproduction?
Asexual reproduction is a process where one parent produces new individuals that are almost exact copies. It does not need two parents.
Bacteria and amoeba can divide into two. Some plants grow from roots, stems, or leaves.
Q32. What Is Vegetative Propagation?
Vegetative propagation is asexual reproduction in plants through roots, stems, leaves, or buds. New plants grow from plant parts.
Money plant, potato, ginger, sugarcane, and bamboo can grow this way. Moist soil and water help growth.
Q33. What Is Sexual Reproduction?
Sexual reproduction involves two parents that produce specialised reproductive cells called gametes. Male and female gametes combine.
The new organism gets genes from both parents. This produces similarity and variation.
Q34. What Are Gametes?
Gametes are specialised reproductive cells that carry half the genetic material of a parent. Male and female gametes combine during fertilisation.
In animals, sperm and eggs are gametes. In flowering plants, pollen and ovules take part in reproduction.
Q35. What Is Fertilisation?
Fertilisation is the joining of male and female gametes to form a zygote. The zygote develops into a new organism.
In plants, fertilisation leads to seed formation. In animals, it starts embryo development.
Q36. Why Don’t Dogs Lay Eggs Like Hens?
Dogs do not lay eggs because their young develop inside the female body. Dogs are mammals.
Hens lay fertilised eggs, and development continues during hatching. Mammals usually give birth to young ones.
Our Home Earth A Unique Life Sustaining Planet Class 8 Extra Questions On Threats
Our home earth a unique life sustaining planet class 8 extra questions often test climate change, pollution, and biodiversity loss. These threats disturb Earth’s balance.
Q37. What Is The Triple Planetary Crisis?
The triple planetary crisis refers to climate change, biodiversity loss, and pollution. These are major threats to life on Earth.
They affect air, water, soil, health, habitats, and ecosystems. Human actions increase these problems.
Q38. What Is Climate Change?
Climate change means long-term changes in temperature, rainfall, and weather patterns. Global warming is a major cause.
Burning fossil fuels releases greenhouse gases. These gases trap extra heat in the atmosphere.
Q39. What Causes Global Warming?
Global warming is caused by excess greenhouse gases trapping more heat in the atmosphere. Carbon dioxide and methane contribute to this.
Burning coal, oil, and gas releases stored carbon. Earth cannot absorb it fast enough.
Q40. How Can Climate Change Affect Life?
Climate change can melt ice caps, raise sea levels, disturb rainfall, and damage habitats. It can affect crops and health.
Some plants and animals may disappear. Coastal cities may face flooding.
Q41. What Is Biodiversity Loss?
Biodiversity loss means the reduction or disappearance of living forms from ecosystems. It weakens nature’s balance.
If grasses disappear, herbivores suffer. Predators then lose food sources.
Q42. How Does Air Pollution Harm Life?
Air pollution harms life by causing breathing problems, crop damage, smog, and acid rain. Vehicles and factories add pollutants.
Polluted air affects humans, animals, and plants. It also damages the environment.
Q43. How Does Water Pollution Harm Life?
Water pollution harms aquatic life and makes water unsafe. Factory waste, farm waste, and plastic waste cause damage.
Polluted water can spread harmful substances through food chains. It also affects human health.
Q44. How Does Soil Pollution Harm Life?
Soil pollution reduces soil quality and crop yield. Excess fertilisers and poor waste disposal damage soil.
Polluted soil can pass harmful substances into food chains. Sustainable farming helps reduce this risk.
Q45. What Can People Do To Protect Earth?
People can save energy, save water, reuse items, repair products, recycle waste, and reduce pollution. Communities can protect natural resources.
Cleaner energy like solar and wind can reduce greenhouse gas emissions. Responsible living supports Earth’s future.
Class 8 Science Chapter 13 MCQ Questions With Answers
class 8 science chapter 13 mcq questions test direct facts from the chapter. Students should read each option carefully.
Q46. What Is One Major Reason Mars Cannot Currently Support Life Like Earth?
Correct answer: It lacks a thick atmosphere and liquid water.
- Mars has a very thin atmosphere.
- Stable liquid water is not present on its surface today.
- These conditions make Earth-like life difficult.
Final Answer: Option iii
Q47. Which Of These Is An Example Of Geodiversity?
Correct answer: Different landforms like mountains, valleys, and deserts.
- Geodiversity refers to non-living Earth variety.
- Landforms, rocks, soils, and processes form geodiversity.
- Bird chirping and fish variety relate to biodiversity.
Final Answer: Option ii
Q48. If Earth Were Smaller With The Same Density, What Might Happen To Its Atmosphere?
Correct answer: It would escape into space due to weaker gravity.
- Smaller Earth would have weaker gravity.
- Weak gravity may fail to hold gases.
- The atmosphere could escape into space.
Final Answer: Option ii
Q49. In Sexual Reproduction, Why Are Offspring Different From Their Parents?
Correct answer: They get mixed instructions from both parents.
- Male and female gametes combine.
- Each parent contributes genetic material.
- This creates variation in offspring.
Final Answer: Option iv
Q50. Which Planet Is The Hottest In The Solar System?
Correct answer: Venus is the hottest planet.
- Venus has a thick carbon dioxide atmosphere.
- This traps heat strongly.
- Venus becomes hotter than Mercury.
Final Answer: Venus
Q51. What Is The Goldilocks Zone?
Correct answer: It is the zone where liquid water can exist.
- It is also called the habitable zone.
- Earth lies in the Sun’s habitable zone.
- Liquid water supports known life.
Final Answer: Habitable Zone
Q52. Which Layer Blocks Harmful Ultraviolet Rays?
Correct answer: The ozone layer blocks harmful ultraviolet rays.
- Ozone is a three-atom oxygen molecule.
- It forms a protective layer in the atmosphere.
- It protects living cells.
Final Answer: Ozone Layer
Q53. Which Earth System Includes All Living Beings?
Correct answer: The biosphere includes all living beings.
- The biosphere includes life on land, water, and air.
- Plants, animals, microbes, and humans belong to it.
- It interacts with atmosphere, hydrosphere, and geosphere.
Final Answer: Biosphere
Important Questions Of Class 8 Science Chapter 13 For Long Answers
Important questions of class 8 science chapter 13 include reasoning and application questions. These answers help students write clear exam responses.
Q54. If There Were No Atmosphere On Earth, What Would Happen?
Without atmosphere, Earth would lose heat, lack breathable air, and face harmful radiation. Life would become extremely difficult.
Atmosphere contains oxygen for respiration. It also supports greenhouse effect and protects Earth with ozone.
Q55. Imagine Earth’s Magnetic Field Suddenly Disappeared. What Problems Could Arise?
Without Earth’s magnetic field, harmful space particles could reach Earth more easily. They could damage the atmosphere and ozone layer.
More harmful UV rays could reach the surface. This would threaten living cells and ecosystems.
Q56. What Three Things Would A Mars Settlement Need To Recreate From Earth?
A Mars settlement would need breathable air, liquid water, and suitable temperature control. It would also need food production systems.
The hardest part may be recreating a stable atmosphere. Mars has a very thin atmosphere.
Q57. How Can Cutting Forests Affect Climate And Biodiversity?
Cutting forests can increase temperature, reduce rainfall stability, damage habitats, and lower biodiversity. It also affects water quality.
Trees help retain soil moisture and support ecosystems. Forest loss can reduce animal and plant survival.
Q58. How Would You Respond To “Global Warming Is Nothing New”?
Natural climate changes happened earlier, but today’s warming has strong human causes. Burning fossil fuels adds extra greenhouse gases.
The current rate of change threatens crops, water, ice caps, sea levels, and biodiversity. Human action matters.
Q59. Where Did Seeds On A School Wall Come From After Monsoon?
Seeds may have come from birds, wind, or animal droppings. Rainwater and cracks helped them germinate.
Seeds need water, air, and suitable conditions. Wall cracks can hold dust and nutrients.
Q60. Give Five Examples Of Vegetative Propagation.
Five examples of vegetative propagation are potato, ginger, money plant, sugarcane, and bamboo. New plants grow from plant parts.
Potato grows from eyes. Ginger grows from rhizome pieces. Money plant grows from stem cuttings.
Our Home Earth A Unique Life Sustaining Planet Notes Class 8
Our home earth a unique life sustaining planet notes class 8 should help students revise major terms quickly. Use this section for fast recall before exams.
Q61. What Are The Four Earth Systems That Sustain Life?
The four Earth systems are atmosphere, hydrosphere, geosphere, and biosphere. These systems interact continuously.
Air, water, soil, rocks, minerals, and living beings depend on each other. Their balance keeps Earth habitable.
Q62. What Is The Difference Between Asexual And Sexual Reproduction?
Asexual reproduction uses one parent, while sexual reproduction uses two parents. Asexual reproduction gives nearly identical offspring.
Sexual reproduction creates variation through mixed genes. This helps life adapt over generations.
Q63. Why Do Fish And Frogs Lay Many Eggs?
Fish and frogs lay many eggs because many young ones may not survive. Water exposes eggs to predators and environmental risks.
Laying many eggs improves the chance that some survive. This supports continuation of the species.
Q64. Why Do Birds Lay Eggs But Mammals Give Birth?
Bird embryos develop inside eggs outside the mother’s body, while mammal embryos usually develop inside the mother’s body. These are different strategies.
Bird eggs contain food for the embryo. Mammals provide nutrition inside the female body.
Q65. Could Plants Grow On Mars If Soil And Water Were Carried There?
Plants would still need suitable air, temperature, pressure, sunlight control, and nutrients. Soil and water alone would not be enough.
Mars has a thin atmosphere and harsh conditions. A controlled habitat would be needed.
Class 8 Science Chapter List