Why Plants Are Called the Lungs of Earth

A simple Class 7 science explanation — photosynthesis, real-life examples, and a hands-on experiment

Have you ever heard people say that plants are the "lungs of Earth"? But why do we call them that? In this article, we will learn in easy words what makes plants so important for life on our planet, how photosynthesis works, and we'll see some real examples and a small experiment you can try in your classroom.

What does the phrase "Lungs of Earth" mean?

When people call plants the "lungs of Earth," they mean that plants play a key role in supplying oxygen to the atmosphere — just like lungs supply oxygen to living bodies. Through a process called photosynthesis, plants take in carbon dioxide (CO₂) and water (H₂O) and convert them into food (glucose) and oxygen (O₂). The oxygen produced is released into the air, which animals and humans use to breathe.

Simple explanation of Photosynthesis

Photosynthesis mainly happens in the green leaves of plants where a pigment called chlorophyll captures sunlight. The simplified chemical equation is:

6 CO₂ + 6 H₂O + (light energy) → C₆H₁₂O₆ + 6 O₂

This means carbon dioxide and water become glucose (a sugar) and oxygen with the help of sunlight.

Why is this important for Earth?

• Oxygen production: Plants release oxygen, keeping the air breathable for all living things.
• Carbon dioxide removal: Plants absorb CO₂, helping to control Earth’s climate.
• Food and habitat: Plants form the base of the food chain and give shelter to animals.

Real-life examples

Trees in a forest: One mature tree can release enough oxygen for 2–4 people each day. A large forest provides oxygen for thousands of living beings.

Phytoplankton in oceans: Tiny ocean plants called phytoplankton produce nearly half of the world's oxygen. So, even the oceans act as the lungs of Earth!

A classroom experiment: Measure oxygen release using pondweed

1. Fill a glass with water and place a small piece of pondweed (Elodea) or a fresh green leaf inside.
2. Keep the glass in sunlight or under a lamp.
3. After a few minutes, tiny bubbles appear on the leaf — that’s oxygen!
4. Count the bubbles per minute to compare how light affects oxygen production.

Tip: More bubbles mean more photosynthesis — sunlight increases bubble count.

Common questions

Q: Do all plants produce oxygen?
A: Most green plants and algae do during the day. At night, they may release some carbon dioxide when they respire.

Q: Are trees more important than small plants?
A: Trees produce more oxygen, but even small plants and algae together make a big difference!

How students can help

1. Plant and care for a tree at school or home.
2. Join clean-up or plantation drives.
3. Reduce paper waste and recycle.
4. Grow native plants — they support local wildlife.
5. Spread awareness about plant importance.

Summary

Plants are called the "lungs of Earth" because they produce oxygen and remove carbon dioxide through photosynthesis. They balance the atmosphere and sustain life. Protecting plants keeps Earth healthy and breathable for everyone.

Try the experiment Download worksheet

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