Chapter 40
Lab #2
Comparing Vertebrate Skeletons
Name ________________________________
Background Information
One characteristic common to all vertebrates is the presence of a skeleton. The endoskeleton provides
support, protects the internal organs, and is a site for the attachment of muscles. In jawless fish, lampreys
and hagfishes, and in sharks and rays, the endoskeleton is made of cartilage. Other vertebrates have
skeletons of bone with small amounts of cartilage present. Similar skeletal features reveal important
evolutionary links among vertebrates. Structures such as bones that have a common origin but a different
function are called homologous structures.
In this investigation, you will compare the skeletons of several different vertebrates and look for evidence
of homologous structures. You will also classify unknown bone specimens based on their similarities to
and difference from known vertebrates.
Problem: To identify homologous bones in vertebrate skeletons.
Procedure
1. Examine the labeled human skeleton in Figure 1. The human skeleton contains more than 200
bones. Identify the bones listed in the diagram on the human skeleton in the lab.
2. Look at the frog skeleton. As you examine the skeleton, compare it to the diagram of the human
skeleton (Figure 1). Ignoring the lines on the diagram, label the bones of the frog skeleton using
the names from the human skeleton.
3.
Repeat step 2 with the skeletons of the lizard, bird, snake fish and mammals seen in Figures 3,
4, 5, 6, 7 and 8.
4.
Answer the questions in Observations and Analysis and Conclusions at the end of this lab.
Complete the following questions on a separate piece of paper and staple to the skeleton handout.
Analysis and Conclusions
1. What are three characteristics that all of the skeletons have in common?
2. How are the vertebral columns of the skeletons similar? How are they different?
3. How do the foot bones of the frog, the lizard, fish and the mammal differ from one another?
4.
How do the functions of the forelimbs differ among the vertebrates you have examined?
5. What type of evidence indicates that the human hand, bird wing, and mammal foot are
homologous structures? Recall that homologous structures are similar in structure but can differ
in function. Homologous structures are clues to common ancestry.
6. Are bones that are similar in structure always similar in function? Give an example from lab that
supports your answer.
7. Which of the skeletons, other than the human, is most closely related to humans? Explain.
1
Figure 1 Human Skeleton
2
Figure 2 Frog Skeleton
Figure 3 Lizard Skeleton
3
Figure 4 Bird Skeleton
Figure 5 Mammal Skeleton
4
Figure 6 Fish Skeleton
Figure 7 Snake skeleton
5
Figure 8 Bat Skeleton
6