Name
Class
Date
Activity: Variation Through Time
Background Information:
Evolution involves changes in offspring over long periods of time. This change is the
result of nature selecting the traits best able to survive in the population and produce offspring.
Through observation of fossil records and comparative studies of organisms it is believed that all
organisms originated from one common ancestor. Over time this ancestor changed and adapted
in many ways to meet the needs of a changing environment. These environmental changes could
have been in shelter, food supply, temperature, etc. This investigation will simulate the
possible directions of change in a population. You will assume that you are a paleontologist who
will organize a collection of related fossils that have changed gradually over time. The
descendants of the common ancestor will study could have changed through a linear sequence or
a branching sequence.
Objectives:
 To observe and compare characteristics of related “fossils”.
 To analyze unity and diversity among related species.
 To create an ancestral line (evolutionary sequence) and determine what environmental
factors could have lead to the resultant changes in the species.
Materials: Masking tape, bulletin board paper, “fossils” from cutout creatures.
Procedure:
1. Obtain a piece of bulletin board paper and cutout the fossils on the creature page.
2. Spread the fossils out on your table so that you can see each one.
3. Study the fossils carefully noting the similarities and differences in structures.
4. Decide on the one fossil specimen that you believe is the one common ancestor to all the
others.
5. Arrange the remaining fossils in a sequence that illustrates gradual change over time in
the related organisms. Your ancestral line may have one, two, three, or more branches
as long as you can justify the connections.
6. When you have finished arranging the fossils tape them to the bulletin board in the same
arrangement.
7. Starting with the common ancestor draw arrows illustrating the lines of descent.
8. Answer the questions.
9. Observe the other arrangements your classmates have created (ask others to justify their
lines of descent).
10. Write your summary.
Questions: Applying Your Knowledge
1. Explain how your own family tree illustrates both unity and diversity, then relate this to
the ancestral “tree” you created with the fossils.
1
2. Select a branched sequence of your ancestral line and imagine and describe the type of
environmental conditions that may have occurred to cause the change in the body
structure.
3. Select a linear sequence of our ancestral line and imagine and describe the type of
environmental conditions that may have occurred to allow only one final organism.
4. Select the last organism in the ancestral line you created (if you have more than one
choose the one that is the most removed from the one common ancestor) and complete a,
b, and c below.
a. State the location on Earth where this organism may have lived.
b. Draw a picture of the organism if it were to evolve further to become better
adapted to live in this environment today
c. Explain the reasons for the adaptations you included in the organism you drew
above.
Summary: Write a three paragraph summary using our standard format (what you were doing in
this activity and why, what you found out by doing this activity, and how this information relates
to your life). Be sure to include how your ancestral line differed from others you saw in the
class and how these differences were possible.
2