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Unit 1: Many Planets, One Earth

Surfaces of Mars, Moon, Venus, Earth. Source: NASA

Surfaces of Mars, Moon, Venus, Earth. Source: NASA

Unit Overview

Astronomers have discovered dozens of planets orbiting other stars, and space probes have explored many parts of our solar system, but so far scientists have only discovered one place in the universe where conditions are suitable for complex life forms: Earth. In this unit, examine the unique characteristics that make our planet habitable and learn how these conditions were created.


Content for This Unit

Online Textbook

  1. Introduction
  2. Many Planets, One Earth
  3. Reading Geologic Records
  4. Carbon Cycling and Earth's Climate
  5. Testing the Thermostat: Snowball Earth
  6. Atmospheric Oxygen
  7. Early Life: Single-Celled Organisms
  8. The Cambrian Explosion and the Diversification of Animals
  9. The Age of Mammals
  10. Further Reading

Printable Online Text for This Unit (PDF)