Name: _________________________________ Date: ___________________ Period: ______________
What do Fossils Tell us About Life in the Past?
Introduction:
As you may know, the Grand Canyon is a huge gorge in northern Arizona. The gorge was created by the Colorado River
during millions of years as the river cut through several layers of sedimentary rock. Imagine that while hiking in the
Grand Canyon you discover a fossil embedded in a rock layer. As you continue hiking, you discover several different
kinds of fossils in several different layers. Your observations raise many questions: why are different kinds of fossils
found in different rock layers? Are certain kinds of fossils found only in certain rock layers? Are any fossils found in all
rock layers?
In this investigation you will have an opportunity to examine several fossils collected from six of the Grand Canyon’s rock
layers and search for trends in the fossil record. The identification of trends should enable you to answer these and
related questions to discover what fossils tell us about life in the past.
Objectives:
1. To discover trends in the fossil record
2. To interpret those trends to test hypotheses about present day life forms
3. To infer the nature of the environments in which the fossilized organisms once lived.
Procedures:
1.
Sort the fossils according to which layer A  G it belongs to.
2. Get a white board for laying out the layers
3. On your white board draw layers for A  G with A at the top and G at the bottom
4. Place each fossil within the appropriate layer.
5. Carefully examine the structure of the fossils, noting similarities and differences of those from different rock
layers. Look for trends and arrange the fossils to best reveal those trends.
6. Draw arrows on the white board to show the possible relationships from one layer to the next.
Analysis of the rock layers and fossils:
1. In general, how to the fossils differ from one layer to the next?
2. Are similar fossils found in several layers?
3. Are some fossils only found in one or two layers?
4. What conclusions can be made about the relative age of the fossils found in the bottom layers of the canyon?
5. What conclusions can be made about the fossils found in the top layers of the canyon? Explain.
6. What trends are revealed when comparing the fossils from one layer to the next layer?
7. Explain why these trends revealed in number 5 have occurred.
8. No fossils were found in the bottom rock layer, layer G. How might you explain this?
9. Suppose that someone generates the hypothesis that present day species were created during a 6 day period by
an act of God. Based on this hypothesis, what should the fossil record look like?
10. Supposed that someone created a hypothesis that present day species arose from fewer, less complex forms
over a considerable period of time. Based on this hypothesis, what should the fossil record look like?
11. Why is it not possible to disprove either of the above mentioned hypotheses?
12. How does this lab about the fossil record help you understand each of the following:
a. Genetic variation:
b. Overproduction of offspring:
c. Survival of the fittest:
d. Differential survival and reproduction:
13. How does this lab about the fossil record help you understand Darwin’s theory of decent with modification?
14. How does this lab about the fossil record help you understand convergent and divergent evolution?