Name: ___________________________
Comparing Vertebrate Skeletons
Introduction
One of the criteria required to be classified as a vertebrate is having an internal skeleton, or endoskeleton. The
endoskeleton has many functions including support, muscle attachment, and protecting vital organs. Not all skeletons are
calcified; some are cartilaginous like in sharks and rays. Some other vertebrates have skeletons with small amounts of
cartilage present.
The arrangement and similarities in bone structure are excellent examples of homologous structures which illustrate
important evolutionary relationships. In this laboratory exercise, you will observe these similarities while analyzing
skeletons and comparing them to your own. You will compare these skeletons and discover the evidence of the
relationships among vertebrates.
Materials
Assorted vertebrate skeletons may be on display but are not required for this exercise.
Pre-Lab Questions
1) Is every individual bone of the human skeleton labeled? Why or why not?
2) Which labels on the human skeleton detail “groups” of bones?
3) How will you go about labeling the other vertebrate skeletons in this lab?
4) Forensic scientists and police officers often need to know the structure of bones. Why?
5) When do you encounter the endoskeletons of other vertebrates in your everyday life?
6) How is knowing the position of your bones important to you?
Procedure
1) Examine the skeleton below. The human skeleton contains 206 bones although not all are labeled individually. Use
these labels as a reference for the skeletons on the following pages.
2) Look at the skeletons on the following pages and compare them to the human skeleton. Once you have observed a
noticeable pattern in their structure, label each skeleton accordingly. Also, take note of the four (4) major bone
types:
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ü
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Long bones are tubular and have an articular surface at each end. The major bones in arms and legs are long
bones.
Short bones are tubular and have an articular surface at each end but are much smaller.
Flat bones are thin and have broad surfaces.
Irregular bones are variable in size and shape. These bones are generally compact in nature and are distributed
throughout the skeleton.
Stop-and-Think Question
Based on its skeletal structure, how does the frog use its limb bones? And the crocodile? Be sure to note their
placement on the axial skeleton.
Stop-and-Think Question
Based on its skeletal structure, how does the pigeon use its limb bones? And the cat? Be sure to note their placement
on the axial skeleton.
Analysis Questions
1) What three major characteristics do all the skeletons share?
2) What are three differences that exist among the skeletons?
3) How are the vertebral columns of the skeletons similar? How are they different?
4) How are the hindlimbs similar? How are they different?
5) How do foot bones of these vertebrates differ from one another? Why?
6) How do the functions of the forelimbs differ among the five vertebrates you examined?
7) What type of evidence indicates that the human hand, pigeon wing, and cat paw are homologous?
8) Are bones that are similar in structure always similar in function? Give an example to defend your answer.
9) Which of the skeletons is most closely related to the human skeleton? What evidence supports your answer?
10) Complete the data table on the following page. Fill out the table by listing the bones the fit each category after
observing and labeling them on the sample skeletons provided. The first box has been completed for you.
Vertebrate
group
à
Human
Bone types
Long
Short
Flat
Irregular
Femur, tibia,
fibula, humerus,
radius, ulna
Frog
Crocodile
Pigeon
Cat