Lab # _____: Fossil Study
Lab skills: 3, 12, 13, 26, 28
Background: Fossils are traces of organisms that lived in the past. When fossils are found,
they are carefully excavated and then analyzed. Most fossils form by one of three methods.
Sometimes the hard structures such as bones, teeth or shells create an imprint in rocks. Another
way fossils are formed is by the replacement of structures in the organism with minerals in a
process known as petrification. The third procedure resulting in the creation of a fossil is simply when the body part is
preserved when sediment covers it. Analysis of fossils includes dating and careful observations of morphology, or the
changes in physical characteristics, so that relations to other fossils or existing organisms can be determined.
The age and morphologies of fossils enable scientists to place the fossils in sequences that show a pattern of changes
that have occurred over time. This relationship is most often depicted in an evolutionary tree. The evolutionary tree
shows relationships between species and the morphological changes that have
occurred between them.
There are two major theories on how evolution takes place. Many scientists believe
that organisms evolve through a process of slow and constant change called
gradualism. Another theory states that some species evolve through the process of
punctuated equilibrium. In punctuated equilibrium, species evolve very rapidly over a
short time and then remain the same for very long periods. Lineage A to C on the
evolutionary tree to the left shows gradualism while A to F shows punctuated
equilibrium.
In this lab you will categorize fossils by similarities in morphology and age. You will
then draw an evolutionary tree that depicts the relationship of these fossils.
Hypothesis: If Crustaceus has evolved, then… (tell me if it will be possible to observe differences in morphology by
examining its fossil record.)
Procedure:
1. Tape together 6 blank sheets of paper along their 27.9 cm edges. Put the tape on the backs! Complete the data
table provided and then title your chart across the top and include your group members’ names.
2. Beneath your title (on the same sheet) you should create column headings for TIME PERIOD, BEGAN, DURATION, AND
FOSSILS going from left to right across the top. The FOSSILS column should be 15 cm in width and the other three
columns should each be 4.3 cm wide.
3. Draw lines to separate the columns that run the length of your chart.
Length of paper = 5 X 21.6 cm = 108.0 cm
Time period
Idahoan (present)
Began (years ago)
30,000
Duration (in years)
30,000
% of total length of paper
3.02%
Actual length
3.3 cm
Californian
80,000
50,000
5.03%
5.4 cm
Montanian
170,000
Colorodian
320,000
Oregonian
395,000
Texian
445,000
Nevadian
545,000
Ohioian
745,000
Wyomingian (oldest)
995,000
15.08%
8.1 cm
50,000
20.10%
27.1 cm
4. The groups of fossils you will work with are fictional animals from the fictional genus Crustaceus. Each fossil on
your fossil sample sheet (on the last page of this lab report) is marked with a time period to which the fossil has
Fossil Study Lab
1
been dated. Cut out each fossil, making sure to include the time period marked below it. You will need this
information later on.
5. Arrange the fossils by age. On your data chart, place each fossil next to the period identified with that fossil. The
term upper means a more recent part of a period. The term lower means an earlier part of a period. Thus, fossils
from an upper period should be placed near the top of the space allotted for that period and those from a lower
period should be placed near the bottom. If the period
identified for a fossil is neither upper nor lower, place the
fossil in the middle of the space. Place fossils from the
same time period side by side.
6. While keeping the fossils in proper age order, arrange
them by morphology. To give you an idea of what body
parts to look for, examine the example of Crustaceus, with
its labeled body parts, in the diagram to the right. Then,
carefully examine the morphology of each fossil. Begin by
examining the oldest fossils, and work in sequence to the
most recent. Note the first 3 changes in morphology
from one time period to the next by drawing a data
table on your answer sheet similar to the one below.
Change in morphology 1
(A) During what time period did the
first noticeable change appear?
Change in morphology 2
(A) During what time period did the
second change appear?
Change in morphology 3
(A) During what time period did the
third change appear?
(B) Describe the change that
appeared.
(B) Describe the change that
appeared.
(B) Describe the change that
appeared.
Arrange the fossils using the following steps:
a. Center the oldest fossil at the bottom of the FOSSILS column.
b. Throughout the chart, those fossils that appear to be exactly the same as fossils preceding them
chronologically should be placed directly in a vertical line with each other.
c. The first fossil that appears different from the one before should be placed slightly to the left of the fossil
before it.
d. During a certain period, the fossils will be split into two branches. In other words, one fossil from that
period will show one type of change, and another fossil from the same period will show a different type of
change. When this occurs, place one of these fossils slightly to the left of the fossil from the preceding
time period and the other slightly to the right.
e. After the point of branching, place each fossil in the left-hand branch that exhibits a change slightly to the
left of the fossil preceding it and for the right-hand branch place each fossil exhibiting change slightly to
the right of the fossil preceding it.
7. Once all of the fossils have been placed correctly according to time and morphology, glue the fossils in place.
8. Draw an evolutionary tree showing how the fictional genus Crustaceus organisms have changed over
time by drawing a stick diagram with dots where fossils are located on your chart. Include all fossils.
Analysis:
A. Briefly describe the evolutionary changes that occurred in Crustaceus during its existence. What features did it
possess in early fossils? What about later ones?
B. During which time period did the fossils start to differentiate into two branches. State the name of the time period and
when it began.
C. In what period does the common ancestor of the Crustaceus species of the Montanian period appear?
D. No examples of Crustaceus species are alive today. During what time period (according to your chart) did the species
become extinct?
E. Did the set of fossils that you arranged show gradualism or punctuated equilibrium? Explain.
Fossil Study Lab
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Crustaceus Sample Fossil Sheet
Fossil Study Lab
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Time period
Began (years
ago)
30,000
Duration (in
years)
30,000
% of total length of paper
(108.0 cm total length)
3.02%
Actual length
Californian
80,000
50,000
5.03%
5.4 cm
Montanian
170,000
Colorodian
320,000
Oregonian
395,000
Texian
445,000
Nevadian
545,000
Ohioian
745,000
Wyomingian (oldest)
995,000
Idahoan (present)
Time period
3.3 cm
15.08%
8.1 cm
50,000
20.10%
27.1 cm
Began (years
ago)
30,000
Duration (in
years)
30,000
% of total length of paper
(108.0 cm total length)
3.02%
Actual length
Californian
80,000
50,000
5.03%
5.4 cm
Montanian
170,000
Colorodian
320,000
Oregonian
395,000
Texian
445,000
Nevadian
545,000
Ohioian
745,000
Wyomingian (oldest)
995,000
Idahoan (present)
Time period
3.3 cm
15.08%
8.1 cm
50,000
20.10%
27.1 cm
Began (years
ago)
30,000
Duration (in
years)
30,000
% of total length of paper
(108.0 cm total length)
3.02%
Actual length
Californian
80,000
50,000
5.03%
5.4 cm
Montanian
170,000
Colorodian
320,000
Oregonian
395,000
Texian
445,000
Nevadian
545,000
Ohioian
745,000
Wyomingian (oldest)
995,000
Idahoan (present)
Fossil Study Lab
3.3 cm
15.08%
8.1 cm
50,000
20.10%
27.1 cm
4