Evolution Revised September 2019 www.BioInteractive.org Page 1 of 2

Click & Learn Student Worksheet

Comparative Anatomy of the Domestic Chicken

INTRODUCTION This worksheet walks through the Click & Learn Comparative Anatomy of the Domestic Chicken, which traces the evolutionary history of birds. By comparing the bone structures of a chicken to those of other species, you will build a simplified evolutionary tree of chickens starting from the last common ancestor of birds and crocodiles.

PROCEDURE Use the information in the Click & Learn to answer the following questions in the space provided. Make sure to read the Introduction, which can be opened from the top-right corner of the Click & Learn.

1. When did birds and crocodiles last share a common ancestor?

2. What types of evidence do scientists examine as they make hypotheses about how organisms are related toone another?

3. What are archosaurs, and what is their defining feature?

4. Archosaurs split into two major groups 250 million years ago. What are those groups?

5. Based on the hip joints shown on the right, is thecrocodile or the dinosaur more similar to the chicken?Describe the similarities you observed.

6. What are some of the similarities and differences between ornithischians and saurischians?

7. Based on the longest digits shown on the right, whichdinosaur group is more similar to the chicken? Describethe similarities you observed.

Comparative Anatomy of the Domestic Chicken

Evolution Revised September 2019 www.BioInteractive.org Page 2 of 2

Click & Learn Student Worksheet

8. Describe how the clavicles, or collarbones, of a chicken are shaped.

9. Based on the clavicles shown on the right, which dinosaurgroup is more similar to the chicken? Describe thesimilarities you observed.

10. Which groups of dinosaurs have fused clavicles, and what does this suggest about chicken evolution?

11. Based on the number of digits shown on the right, whichdinosaur group is more similar to the chicken? What isone example of a dinosaur from the group you selected?

12. Is a chicken more like a Velociraptor or a T. rex? Useevidence from the pubis bones shown on the right tojustify your answer.

13. Chickens and other birds have a reduced and fused tailcalled a pygostyle. Which group of dinosaurs also has apygostyle? What other traits does that group have incommon with birds?

14. Examine the final evolutionary tree you built, which can be viewed by opening the Progress section in thetop-right corner of the Click & Learn. What is one shortcoming of this proposed tree?