49
Lesson 49 of 84 · U.S. Regions
State Parks and Landmarks
Coral reefs, built by tiny polyps, are underwater ecosystems. The Great Barrier Reef, the largest living structure on Earth, supports thousands of marine species.
Key Facts
1
Geography affects how people live.
2
Earth has seven continents.
3
There are five major oceans.
Check Your Understanding
Question 1
1 of 2Which is the largest ocean?