UNIT OVERVIEW

Why do fish lay thousands of eggs while elephants have only one calf every few years? Why do some snakes lay eggs while others give birth to live young?

Different animals reproduce in different ways. Each way of reproducing helps that animal survive in its specific environment. In this unit, you will learn about the different ways vertebrates (animals with backbones) reproduce. You will see how these strategies help animals succeed in places as different as oceans, deserts, and forests.

What you will learn:

By the end of this unit, you will be able to:

• Explain the difference between external and internal fertilisation
• Compare three types of development: ovipary, ovovivipary, and vivipary
• Describe the structure and function of the amniotic egg
• Explain the difference between precocial and altricial offspring
• Evaluate how different reproductive strategies help animals survive in different environments

What you need to know already:

• Meiosis and how gametes (sex cells) are produced (Grade 12, Term 1)
• Basic sexual reproduction (Grade 9)
• Cell division (Grade 10)

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