If two different species of fish fossils were found in two different layers of sedimentary rock, what might one infer about the specimens?

Question

A. The species in lower layer died first
B. They died at the same time
C. The species in the higher layer evolved from the species in the lower layer
D. The species in the higher layer died first
E. The two species are unrelated

Clarify Question
1. What is the key concept addressed by the question?
2. What type of thinking is required?
3. What key words does the question contain and what do they mean?

Gather Content
1. •What do you know about relatedness based on location in a rock layer?How does it relate to the question?

Consider Possibilities
1. What other information is related to the question? Which information is most useful?

Choose Answer
1. Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
1. Did your problem-solving process lead you to the correct answer? If not, where did the process break
down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A. The species in lower layer died first

Clarify Question
1. The question is about the formation of fossils.
2. This question is asking you to apply the principles of fossil
formation to interpret data.
3. Fossils found at different layers of sedimentary rock.

Gather Content
1. Sedimentary rock forms when sediment (silt and sand) drops to the bottom of a lake or ocean, covering whatever is on the bottom of the lake or ocean. In general when fossils are found in different
layers, the older fossils are found at the bottom.

Consider Possibilities
1. In sedimentary rock the upper layers are newer. Whether or not the two different species are related does not impact what layer they are found in, and you also cannot assume that one evolved from the other.

Choose Answer
1. Sediments form at the bottom of a lake and accumulate over time. Thus the older fossils are in the older layer and these organisms died before those in the upper layer.

Reflect on Process
1. This question asked you to apply your understanding of fossil formation to predict the relative age of
different fossils.If you got the correct answer, great job! If you got an incorrect answer, where did you
get stuck? Did you recall that as sedimentary rock forms it traps dead animals that can then become
fossils?