Class 8 Science Chapter 13 Our Home Earth, explains what makes Earth unique and why life exists only on this planet. It focuses on how Earth’s systems work together to support and sustain life.
From microscopic organisms to giant whales, and from forests to oceans, Earth supports a wide variety of life forms. Air, water, soil, sunlight, the atmosphere, Earth’s magnetic field, and reproduction play a vital role in maintaining this balance.
The chapter also highlights major environmental threats such as climate change, pollution, and biodiversity loss, and emphasizes the need for humans to protect and conserve our planet.
Our Home Earth Worksheet
Our worksheets include different types of practice questions like MCQs, fill in the blanks, true or false, and short and long answers. Based on the latest curriculum, they help students think critically through concept-based activities, easy experiments, and real-life examples, making learning meaningful and effective.
With our engaging and well-structured worksheets, students can reinforce their classroom learning, prepare for exams, and develop a strong foundation in science.
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Science Class 8 Chapter 13 Study Notes
Why is Earth a Unique Planet?
Earth is the only known planet where life exists.
Reasons Earth is special:
- Life exists only on a thin crust of the planet (as thin as the skin of an apple).
- Earth provides air, water, soil, minerals, and suitable temperature.
- Earth’s satellites help us observe temperature, vegetation, ocean colour, pollution, and wind patterns.
- Earth’s crust, though very thin, supports all life forms.
How Do Other Planets Look?
- The solar system has eight planets.
- Inner rocky planets: Mercury, Venus, Earth, Mars
- Outer gas giants: Jupiter, Saturn, Uranus, Neptune
Important points:
- Planets closer to the Sun are hotter.
- Venus is the hottest planet (450°C)—not because it is closest to the Sun, but due to its thick CO₂ atmosphere causing an extreme greenhouse effect.
- Greenhouse effect keeps Earth warm and allows life.
What Makes Earth Suitable for Life?
(a) Distance from the Sun – The Goldilocks Zone
- Earth lies in the habitable zone where water exists as liquid.
- Too close → water evaporates.
- Too far → water freezes.
- Earth appears blue due to water.
(b) Size of the Earth
- Earth’s gravity is just right:
- enough to hold an atmosphere
- not so much that life gets crushed
- Atmosphere protects life by providing oxygen and supporting weather.
- Ozone layer blocks harmful UV radiation.
(c) Magnetic Field of Earth
- Earth behaves like a giant magnet.
- Molten iron in the core generates magnetic field.
- Magnetic field protects Earth from:
- solar wind
- cosmic rays
- Without magnetic field, atmosphere would be stripped away.
What Allows Life to Be Sustained?
Air, Water, and Sunlight
- Atmosphere contains oxygen for respiration.
- Plants use sunlight + CO₂ + water → photosynthesis → oxygen.
- Greenhouse effect keeps Earth warm enough for liquid water.
- Hydrosphere supports aquatic life, weather, and rainfall.
Soil, Rocks, Minerals (Geosphere)
- Provide nutrients (nitrogen, potassium).
- Geodiversity → different habitats (mountains, deserts, valleys).
- Soil forms slowly from breakdown of rocks and dead matter.
Plants, Animals, Microorganisms (Biosphere)
- All life forms interact with their environment.
- Food chains and food webs maintain balance.
- Decomposers recycle nutrients.
Balance of Earth Systems
- Air + Water + Soil + Living things → interconnected
- Example: cutting forests affects rainfall, soil fertility, biodiversity.
What Keeps Life from Disappearing?
Asexual Reproduction
One parent → identical offspring.
Examples:
- Vegetative propagation: potato, ginger, money plant
- Microbes: bacteria, amoeba
- Simple animals: Hydra (budding), planaria (regeneration)
Sexual Reproduction
- Two parents (male + female).
- Mix of genes → variations → evolution.
- Plants: pollen (anther) + ovule (inside flower) → fertilisation → seed.
- Animals: sperm + egg → zygote → embryo.
Differences:
- Birds lay eggs; embryo develops outside.
- Mammals give birth; embryo develops inside mother.
Threats to Life on Earth
(a) Climate Change
- Caused by greenhouse gases from burning fossil fuels.
- Effects: melting ice caps, rising sea levels, extreme weather.
(b) Biodiversity Loss
- Habitat destruction → species extinction.
- Disrupts food chains and ecosystems.
(c) Pollution
- Water pollution
- Air pollution → smog, acid rain
- Soil pollution → reduced crop yield
Protection Measures
- Montreal Protocol, Kyoto Protocol, Paris Agreement
- Reduce pollution, renewable energy, recycling
- Conserving ecosystems and biodiversity
Our Home Earth Question Answers
Q1. Why is Earth called a unique planet?
Ans: Earth is called a unique planet because it has the right temperature, liquid water, atmosphere, magnetic field, and suitable conditions that support life.
Q2. What is the greenhouse effect?
Ans: The greenhouse effect is the process by which gases like carbon dioxide trap heat in Earth’s atmosphere, keeping the planet warm enough to support life.
Q3. Define the habitable (Goldilocks) zone.
Ans: The habitable or Goldilocks zone is the region around a star where temperatures allow water to exist in liquid form, making life possible.
Q4. Describe the role of the ozone layer and magnetic field in protecting life on Earth.
Ans: The ozone layer absorbs harmful ultraviolet rays from the Sun, preventing damage to living cells. Earth’s magnetic field deflects charged particles from the solar wind and cosmic rays, protecting the atmosphere from being stripped away and ensuring life can survive.
Q5. Explain how air, water, and sunlight together support life on Earth.
Ans: Air provides oxygen for respiration and carbon dioxide for photosynthesis. Water is essential for all life processes and helps regulate temperature. Sunlight provides energy for photosynthesis, which produces food and oxygen. Together, these elements support all living organisms.