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 Arrangement of Bones in Limb (Clumped, Even, etc) / Function of Limb
Human
Lizard
Cat
Whale
Bat
Frog
Bird
  1. Analyzing Observations: Which limbs in the table perform similar functions? How do the bone arrangements compare?
  1. Identifying Relationships: Which is the better indicator of the relationship between two organisms—structure or function? Explain your reasoning.
  1. 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 # / Human / Chimpanzee / Gorilla / Monkey / Horse
87 / THR / THR / THR / GLN / ALA
88 / LEU / LEU / LEU / LEU / LEU
89 / SER / SER / SER / SER / SER
90 / GLU / GLU / GLU / GLU / GLU
91 / LEU / LEU / LEU / LEU / LEU
92 / HIS / HIS / HIS / HIS / HIS
93 / CYS / CYS / CYS / CYS / CYS
94 / ASP / ASP / ASP / ASP / ASP
95 / LYS / LYS / LYS / LYS / LYS
96 / LEU / LEU / LEU / LEU / LEU
97 / HIS / HIS / HIS / HIS / HIS
98 / VAL / VAL / VAL / VAL / VAL
99 / ASP / ASP / ASP / ASP / ASP
100 / PRO / PRO / PRO / PRO / PRO
101 / GLU / GLU / GLU / GLU / GLU
102 / ASN / ASN / ASN / ASN / ASN
103 / PHE / PHE / PHE / PHE / PHE
104 / ARG / ARG / LYS / LYS / ARG
105 / LEU / LEU / LEU / LEU / LEU
106 / LEU / LEU / LEU / LEU / LEU
107 / GLY / GLY / GLY / GLY / GLY
108 / ASN / ASN / ASN / ASN / ASN
109 / VAL / VAL / VAL / VAL / VAL
110 / LEU / LEU / LEU / LEU / LEU
111 / VAL / VAL / VAL / VAL / ALA
112 / CYS / CYS / CYS / CYS / LEU
113 / VAL / VAL / VAL / VAL / VAL
114 / LEU / LEU / LEU / LEU / VAL
115 / ALA / ALA / ALA / ALA / ALA
116 / HIS / HIS / HIS / HIS / ARG
  1. 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
  1. In the study of hemoglobin, which vertebrate is most closely related to humans? Least closely related?
  1. Besides looking at amino acid sequences, what are some other methods biologists use to determine evolutionary relationships?
  1. 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?
  1. If the amino acid sequences are similar in gorillas and humans, will the nucleotide sequence of DNA also be similar? Why or why not?
  1. 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 / Annual Antibiotic Usage / Percent Resistant Strains
1978 / 0.84 / 0
1979 / 0.92 / 2
1980 / 1.04 / 29
1981 / 0.98 / 46
1982 / 1.02 / 45
1983 / 1.03 / 58
1984 / 0.95 / 61
1985 / 1.12 / 60
1986 / 1.06 / 49
1987 / 1.14 / 59
1988 / 1.21 / 58
1989 / 1.28 / 71
1990 / 1.32 / 84
1991 / 1.31 / 79
1992 / 1.27 / 78
1993 / 1.28 / 91
  1. Graph these data in two different graphs: A) antibiotic usage vs. year (antibiotic usage onthe y-axis, year on the x-axis) and B) percent resistant strains vs. year (percent resistantstrains on the y-axis, year on the x-axis). Give your graphs a title and caption explaining the overall trends observed.
  1. From these data, do you think these two factors (antibiotic usage and percentage ofstrains resistant to the antibiotics) are related?
  1. What appears to be the force that led to this evolution in the bacterial population?
  1. In another study, also in Finland, researchers investigated the effect of greatly limitingthe 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). Afterantibiotic usage was greatly decreased, the percentage of bacterial strains that wereresistant to this antibiotic was decreased by 50% (cut in half). What does this newinformation tell you?