UNIT OVERVIEW

Earth is about 4.6 billion years old. During this time, the planet has changed in many ways. Continents have moved. The air we breathe has changed. Living things have appeared, changed, and sometimes disappeared forever.

In this unit, you will learn how scientists use fossils and other evidence to understand this long history. South Africa has some of the world's most important fossil sites. These sites help us understand how life began and how it changed over time.

What you will learn:

• How Earth's atmosphere, climate, and land have changed over time
• The three main geological eras and what makes each one important
• What the Cambrian explosion was and why it matters
• What mass extinctions are and what causes them
• How fossils form and how scientists find out how old they are
• Important fossil sites in South Africa and what they tell us

What you should already know:

• The difference between prokaryotic and eukaryotic cells
• The five kingdoms of life
• Basic ideas about ecosystems and biodiversity

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