Name:
Date:
Period:
Accelerated Biology
Analyzing Evidence for Evolution
Objectives:
 Identify the differences in the amino-acid sequences of the hemoglobin protein of several species
 Infer the evolutionary relationships among several species by comparing amino-acid sequences of the
same protein in different organisms
 Describe structures of different organisms
 Identify relationships between the structures of different organisms
 Identify relationships between antibiotic usage and resistance
Purpose:
You are a zoologist who specializes in the classification of vertebrates according to their evolutionary
relationships. In your research, you examine both the anatomy of organisms and the amino-acid sequences of
proteins found in vertebrates to determine the degree of biochemical similarity between vertebrate species.
Today you will compare the anatomy of the limbs and also portions of the protein hemoglobin. Your goals are
to deduce the evolutionary relationships among the species given.
Part 1: Anatomy of vertebrate limbs
1. Observe the forelimbs of the seven different animals shown in the diagrams below. Look for each of
the characteristics listed in the data table, and record your observations.
Animal
# of Bones in
Upper Limb
(above elbow)
# of Bones in
Lower Limb
(Below elbow)
General
Function of Limb
Arrangement of
Bones in Limb
(Clumped,
Even, etc)
Human
Lizard
Cat
Whale
Bat
Frog
Bird
2. Analyzing Observations: Which limbs in the table perform similar functions? How do the bone
arrangements compare?
3. Identifying Relationships: Which is the better indicator of the relationship between two organisms—
structure or function? Explain your reasoning.
4. Inferring: Are these structures analogous or homologous? How do you know?
Part II: Amino Acid Sequence of Hemoglobin
1. Look at the amino acid sequences shown below. These sequences are portions of the hemoglobin
molecules of five organisms. The portions of the chains shown are from amino acid number 87 to
amino acid number 116 in a sequence of 146 amino acids.
AA #
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
Human
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
Chimpanzee
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
Gorilla
THR
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ASN
PHE
LYS
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
Monkey
GLN
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ASN
PHE
LYS
LEU
LEU
GLY
ASN
VAL
LEU
VAL
CYS
VAL
LEU
ALA
HIS
Horse
ALA
LEU
SER
GLU
LEU
HIS
CYS
ASP
LYS
LEU
HIS
VAL
ASP
PRO
GLU
ASN
PHE
ARG
LEU
LEU
GLY
ASN
VAL
LEU
ALA
LEU
VAL
VAL
ALA
ARG
2. Compare the amino-acid sequence of the human hemoglobin molecule with that of each of the other
four vertebrates. For each vertebrates’ sequence, count the number of amino acids that differ from
the human sequence and list them in the table below. Be sure to list the animal species in descending
order according to their degree of evolutionary closeness to humans.
Hemoglobin Amino-Acid Sequence Similarities Between Humans and Other Vertebrate Species
Species
Number of differences from human hemoglobin
3. In the study of hemoglobin, which vertebrate is most closely related to humans? Least closely related?
4. Besides looking at amino acid sequences, what are some other methods biologists use to determine
evolutionary relationships?
5. When the portions of the gorilla and human hemoglobin were compared, there was only one
difference in the amino-acid sequence. What could have been responsible for this change?
6. If the amino acid sequences are similar in gorillas and humans, will the nucleotide sequence of DNA
also be similar? Why or why not?
7. How is biochemical comparison (comparing amino acid sequences) different from other methods of
determining evolutionary relationships?
Part III: Observed Natural Selection
In this exercise, you will interpret real data on antibiotic resistance. These data points were collected from a
community in Finland from 1978 – 1993. The researchers collected data on the annual amount of antibiotics
used in this community. They also collected samples of bacteria from young children with middle ear
infections. They then examined the bacterial strains to see if they were susceptible to (killed by) or resistant to
(not killed by) these antibiotics. The data given below are a measure of the amount of antibiotics used each
year, and the percentage of the bacterial strains that were found to be resistant to the antibiotic (between 0 –
100%).
Year
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
Annual Antibiotic Usage Percent Resistant Strains
0.84
0
0.92
2
1.04
29
0.98
46
1.02
45
1.03
58
0.95
61
1.12
60
1.06
49
1.14
59
1.21
58
1.28
71
1.32
84
1.31
79
1.27
78
1.28
91
1. Graph these data in two different graphs: A) antibiotic usage vs. year (antibiotic usage on the y-axis,
year on the x-axis) and B) percent resistant strains vs. year (percent resistant strains on the y-axis, year
on the x-axis). Give your graphs a title and caption explaining the overall trends observed.
2. From these data, do you think these two factors (antibiotic usage and percentage of strains resistant
to the antibiotics) are related?
3. What appears to be the force that led to this evolution in the bacterial population?
4. In another study, also in Finland, researchers investigated the effect of greatly limiting the use of an
antibiotic on a community (kids still got ear infections, but they now used a “wait and see” approach to
see if the infection would clear up on its own). After antibiotic usage was greatly decreased, the
percentage of bacterial strains that were resistant to this antibiotic was decreased by 50% (cut in half).
What does this new information tell you?