Introduction to Amniotes

Identify characteristics of amniotes

Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals. Amniotes are characterized by having an egg equipped with an amnion, an adaptation to lay eggs on land or retain the fertilized egg within the mother.

Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In eutherian mammals (such as humans), these membranes include the amniotic sac that surrounds the fetus. These embryonic membranes and the lack of a larval stage distinguish amniotes from tetrapod amphibians.

What You’ll Learn to Do

  • Identify the classes of animals that are amniotes
  • Describe the main characteristics of amniotes
  • Discuss the evolution of amniotes

Learning Activities

The learning activities for this section include the following:

  • Amniotic Animals
  • Evolution of Amniotes
  • Self Check: Amniotes