83
Lesson 83 of 84 · U.S. Regions
Rivers That Define Regions
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
There are five major oceans.
2
Climate differs from weather.
3
Natural resources are limited.
Check Your Understanding
Question 1
1 of 2What are natural resources?