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š¬ Think about it
Take a deep breath. Sip some water. Feel the sunlight. These three are so common we forget them. Yet without them, no life could survive. Let us see how air, water and sunlight keep life going.
How do air and sunlight support life?
- The atmosphere has oxygen, used by humans, animals and plants for respiration.
- In sunlight, plants take carbon dioxide and water to make food.
- This process is photosynthesis, and it releases oxygen.
- So air and sunlight keep the cycle of life going.
Photosynthesis Keeps Life Going
Sunlight, carbon dioxide and water
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Plants make food
Photosynthesis happens in the leaves.
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Oxygen released
This oxygen is used for respiration.
Why is water so important for life?
- Water covers about 70 per cent of Earth's surface.
- All this water together forms the hydrosphere.
- It carries nutrients in plants and helps body functions in animals.
- So water is essential for health and life.
How does the greenhouse effect help keep Earth warm?
- Radiation from the Sun heats the Earth.
- Some heat is trapped by the atmosphere through the greenhouse effect.
- This keeps the temperature high enough for liquid water.
- Without an atmosphere, Earth would lose heat and become too cold.
Example:
The atmosphere works like a warm quilt, holding in just enough of the Sun's heat for life.
Important Points
- Oxygen in the air is used for respiration.
- Water covers about 70 per cent of Earth and forms the hydrosphere.
- The greenhouse effect keeps Earth warm enough for liquid water.
ā Test Yourself
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What gas in the air is used for respiration?
View Answer
Oxygen. -
What is the hydrosphere?
View Answer
All the water on Earth together — oceans, rivers, lakes and groundwater. -
How much of Earth's surface is covered by water?
View Answer
About 70 per cent. -
What do plants make in sunlight?
View Answer
Food, by photosynthesis, releasing oxygen. -
What would happen to Earth without an atmosphere?
View Answer
It would lose heat to space and become too cold.
Important Definitions
- Hydrosphere — all the water on Earth, in oceans, rivers, lakes and underground.
- Photosynthesis — the process by which plants use sunlight, carbon dioxide and water to make food.
