wunder beta

🐠 Coral Reefs

Discover the tiny animals that build the ocean's most colorful cities.

lessons

~15 min

to learn

🔬 Science

subject

Ages 6–12

level

Start the course →

What you’ll learn

Explain how coral polyps build reefs and get their color.Coral reefs are built by tiny animals called polyps that make limestone skeletons from seawater calcium. Colorful algae called zooxanthellae live inside them and share food. The Great Barrier Reef is the largest reef system on Earth.
Describe why reefs matter and what causes coral bleaching.Reefs shelter about a quarter of all ocean species. When water gets too warm, corals expel their algae and turn white, a process called bleaching driven by climate change. People protect reefs by growing new corals and reducing pollution and warming.

Questions this course answers

What actually builds a coral reef?

Coral reefs are built by tiny animals called coral polyps that live together in huge colonies.

How do hard corals build their skeletons?

Hard corals take calcium from seawater to make a limestone skeleton.

What are the tiny algae inside corals called?

Microscopic algae called zooxanthellae live inside coral tissues and give them color and food.

Why are coral reefs called the rainforests of the sea?

Reefs are home to about a quarter of all ocean species, making them extremely rich in life.

What is coral bleaching?

When stressed, corals expel their algae, exposing the white skeleton beneath their clear tissue.

What is the main cause of coral bleaching?

Rising ocean temperatures from climate change are the primary cause of coral bleaching.

Grounded in trusted sources

Encyclopaedia Britannica Kids, 'coral reef' (kids.britannica.com/students/article/coral-reef/633865)
Great Barrier Reef Foundation, 'What is coral bleaching?' (barrierreef.org/news/explainers/what-is-coral-bleaching)
Great Barrier Reef Foundation, 'Coral Bleaching' (barrierreef.org/the-reef/threats/coral-bleaching)
Encyclopaedia Britannica, 'How and Where Coral Bleaching Is Affecting the Great Barrier Reef' (britannica.com)

Every Wunder lesson is built from real, reputable sources — never invented.

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