wendystjohn

To deepen your understanding of how life on Earth has evolved over time, watch the video below.

Then, work through this interactive website, and answer the questions in your worksheet: http://media.hhmi.org/biointeractive/click/great-transitions/

  1. Tetrapods are _______. Examples of tetrapods include:
  2. Tetrapods first appear in the fossil record ________ million years ago.
  3. Charles Darwin predicted that tetrapods evolved from _____________. What observation leads to that hypothesis?
  4. What evidence would you expect to find to support that hypothesis? What age rocks would you look in and why?
  5. Fish use _________ to breathe underwater. (However, many species of lobe-finned fishes that evolved during the Devonian period also had __________)
  6. In fossils, what anatomical evidence indicates that gills were present?
  7. Tetrapods use __________ to breathe. Do any modern tetrapods have gills? Explain.
  8. Why is a sturdy ribcage important for tetrapods?
  9. What is homology? To what are fins homologous?
  10. Most modern tetrapods have ________ digits on front limbs and _______ digits on back limbs, although some species have fewer. How does this number compare to the number of digits on the limbs of transitional fossil forms?
  11. Why do many of the transitional fossils between fish and tetrapods have flat heads?
  12. How did the anatomy of the shoulder and head change during tetrapod evolution?
  13. _________________ and _______________ are fossil species have characteristics unique to fish as well as characteristics found in fish and tetrapods. Describe the characteristics of lobe-finned fish that are similar to those of tetrapods.
  14. Which lobe-finned fish is alive today? __________________
  15. Acanthostega and Icythyostega have been called fish-like tetrapods. Explain why they are described as such and describe the environment in which they probably lived.
  16. Why is Tiktaalik such an important transitional fossil?
  17. __________________ and _____________________ are early tetrapods that do not have features unique to fish. Describe how these two species differ anatomically and what that means about where they each lived.