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Lesson 16.4
Hands-On 13
Comparing Bones
Goal
Identify homologous bones in vertebrate forelimbs.
Build Connections
The term forelimb refers to the front leg or arm of a vertebrate. The bones in the forelimbs
of modern vertebrates are homologous. These forelimbs evolved from the forelimbs of an
extinct lobe-finned fish that lived more than 380 million years ago. If modern vertebrates all
had different origins, it would be unlikely for them to have such similar structures.
In this activity, you will compare the bones in the forelimb of a human, cat, and lizard.
Skills Focus
Use Models, Compare and Contrast
Materials

scissors

tape
Safety
Do not direct the points of the scissors toward yourself or others. Use the scissors only as
instructed.
Procedure
Look at the diagram of the human arm. Note how the upper arm (humerus), lower arm (ulna
and radius), and hand bones fit together. Use the diagram as a model to help you piece
together the forelimbs of a cat and lizard.
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1.
Cut out the drawings of bones on page 359.
2.
Move the parts around to form a cat forelimb and a lizard forelimb. NOTE: The
drawings are not drawn at actual size.
3.
After you have pieced together both forelimbs, tape the limbs onto a sheet of
notebook paper. Label the parts of each forelimb and add a label for the animal
name.
Analyze and Conclude
1.
Interpret Visuals How did the drawing of the human arm help you assemble the cat
and lizard forelimbs?
2.
Classify Describe how you decided which bones belonged to which animal.
3.
Compare and Contrast Describe the similarities among the three forelimbs. How
would these compare in actual size?
4.
Compare and Contrast Use your structures and your experience to compare the
ways that the three species use their forelimbs.
Build Science Skills
How do these homologous structures provide evidence to support the theory that vertebrates
evolved from a common ancestor?
358
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359
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360
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