MK DOM: Background and rocedures hylogeny, volution, and omparative natomy. oncept: Modern classification is based on evolution. B. Background: One way to discover how groups of organisms are related to each other (phylogeny) is to compare the anatomical structures (body organs and parts) of many different organisms. orresponding organs and other body parts that are alike in basic structure and origin are said to be homologou structures(for example, the front legs of a horse, wings of a bird, flippers of a whale, and the arms of a person are all homologous to each other). When different organisms share a large number of homologous structures, it is considered strong evidence that they are related to each other. When organisms are related to each other, it means they must have had a common ancestor at some time in the past. f there are specific modifications of those features shared by different groups of organisms, we say that those features are shared derived characters. When we do studies in comparative anatomy, and find different numbers of shared derived characters exist between different groups, we can draw a diagram of branching lines which connect those groups, showing their different degrees of relationship. These diagrams look like trees and are called "phylogenetic trees" or " cladograms" (-doe-grams). The organisms are at the tips of the stems. The shared derived features of the homologous structures are shown on the cladogram by solid square boxes along the branches, and common ancestors are shown by open circles. The more derived structures two organisms share, the closer is their evolutionary relationship -- that is, the more recently their common ancestor lived. On the cladogram, close relationships are shown by a recent fork from the supporting branch. The closer the fork in the branch between two organisms, the closer is their relationship.. Objectives: iven some groups of organisms and some of their distinguishing characteristics, you will construct a cladogram, and properly interpret and analyze that cladogram in terms of how it shows common ancestry and degrees of evolutionary relationship. D. rocedure: tep 1. sing online resources and the explanations below, determine which of the characteristics each animal has. n the Data Table provided (on your ladogram Worksheet), place an "x" in the box if the animal has the characteristic. xplanations of haracteristics: set #1: set #2: set #3: set #4: set #5: set #6: set #7: Dorsal nerve cord (running along the back or "dorsal" body surface) otochord (a flexible but supporting cartilage-like rod running along the back or "dorsal" surface) aired appendages (legs, arms, wings, fins, flippers, antennae) ertebral column ("backbone") aired legs mnion (a membrane that holds in the amniotic fluid surrounding the embryo; may or may not be inside an egg shell) Mammary glands (milk-secreting glands that nourish the young) lacenta (structure attached to inside of uterus of mother, and joined to the embryo by the umbilical cord; provides nourishment and oxygen to the embryo) anine teeth short (same length as other teeth) Foramen magnum forward (spinal cord opening, located forward, under skull) 1
tep 2: Below the Data Table on your Worksheet, make a enn diagram, placing your seven animals in groups to illustrate those characteristics which different animals have in common. ee example below: Tuna: Backbone orse: lacenta uman: Foramen magnum forward tep 3: sing the enn diagram of the groupings just completed (as a guide), draw a cladogram on the back of your Worksheet to illustrate the ancestry of these animals. The diagram should reflect shared characteristics as time proceeds. n example is shown below. otice how the different animals are all at the same time level (across the top) since they all live today. xample of ladogram T O M TM Foramen magnum forward Backbone lacenta # OF D TT. ummary: On the back of your Worksheet, explain at least three types of information which can be obtained from a cladogram. F. pplication: Three previously unknown vertebrates have been discovered in a rain forest in outh merica. One animal is very similar to an iguana lizard. The second animal resembles a large rat. The third is similar to a goldfish. lace these animals on your cladogram and explain why you placed them where you did (on back of the Worksheet).. xtension: f you need further practice, your teacher may provide you with another set of organisms and their distinguishing characteristics. On a separate sheet, prepare a table for analyzing the data, draw a enn diagram, and draw a cladogram for those organisms, similar to the work done above. 2
ame tep 1: DT TB T TT Koala agfish T 1 Dorsal erve ord otochord T 2 aired ppendages ertebral column T 3 aired legs T 4 mnion (mniotic sac) T 5 Mammary lands T 6 lacenta T 7 anine teeth short Foramen magnum fwd TOT of Xs--------> tep 2: enn Diagram: DOM WOKT nimals quirrel Monkey alamander orilla Date er. Mud Turtle unfish 3
tep 3: ladogram:. pplication: (For each new vertebrate, add its branch line and name in the appropriate place in the cladogram drawn above). ow, give a reason for placing each where you did. "guana-like" animal: "at-like" animal: "oldfish-like" animal: 4
More ractice with ladograms sing mino cid equences to how volutionary elationships: ntroduction With advances in molecular biology, scientists are able to take a closer look at similarities among organisms and to look for evolutionary relationships at the molecular level. The amino acid sequence of a protein can be examined in much the same way as the derived traits shown in the previous sections, and a cladogram can be constructed based on the number of differences in the sequences. xamine the data table below, which shows the number of differences in the amino acid sequence of a protein called cytochrome c between fruit flies and other organisms, and the cladogram made from it (on the next page). pecies # of amino acid differences from fruit fly Dogfish shark 26 igeon 25 crewworm fly 2 ilkworm 15 Tobacco hornworm 14 Wheat 47 1. s you move from left to right in this cladogram, what happens to the number of difference amino acid sequences? 2. Which species is most closely related to the fruit fly? ladogram of cytochrome c amino acid sequence comparison ilkworm Tobacco hornworm crewworm fly Fruit fly igeon Dogfish hark Wheat
ractice mino cid ladogram ow you will practice constructing a cladogram based on the amino acid differences in cytochrome c between chimpanzees and other animals. se the data table to construct your cladogram. our cladogram should look similar to the one above when you are finished. pecies # of amino acid differences from fruit fly Fruit Fly 29 orse 12 attlesnake 14 ed Bread Mold 48 hesus monkey 1 crewworm fly 27 napping Turtle 15 Tuna 21 Wheat 43 ladogram of ytochrome c mino acid sequence comparisons to chimpanzees himpanzee
ow you are ready to construct a cladogram from amino acids. Follow the procedure below. 1. xamine the amino acid relationship for part of the hemoglobin in the table below. ou will be comparing the other animals to human beings and determining cladistic relationships between them. ircle any differences in the amino acid sequence between the animals and humans. pecies MO D Q uman T O orilla T O orse O Kangroo O hesus Monkey O 2. dd up the total differences for each species and complete the table below. 3. onstruct a cladogram in the box below pecies # of amino acid differences from human orilla orse Kangaroo hesus monkey
1. Based on the hemoglobin data above, which animal is most closely related to humans? xplain your answer. 2. Based on the hemoglobin data above, which animal is least closely related to humans? xplain your answer. 3. imilarities in amino acid sequence between organisms, means that there will also be similarities in D sequence. Why?
volution & ature of cience nstitutes (/) esson lan: Making ladograms K TO DT TB K TO T WOKT nimals hesus Monkey Bullfrog uman napping Turtle T TT Kangaroo amprey Tuna T 1 Dorsal erve ord otochord X X X X X X X T 2 aired ppendages ertebral column X X X X X X T 3 aired legs X X X X X T 4 mnion (mniotic sac) X X X X T 5 Mammary lands X X X T 6 lacenta T 7 anine teeth short Foramen magnum fwd TOT of Xs--------> 5 1 6 3 7 4 2 X X X tep 2: enn Diagram: uman: foramen magnum fwd... hesus Monkey: placenta Kangaroo: mammary glands napping Turtle: amnion Bullfrog: paired legs Trout: paired appendages... amprey: dorsal nerve cord... 5
volution & ature of cience nstitutes (/) esson lan: Making ladograms K TO T DOM: The resulting cladogram should look something like the one shown below (with or without the vertical TM axis and horizontal # OF D TT. ou can use this to make an overhead for subsequent class discussion. DOM M T B FO TT KOO MOK M T 7 T 6(lacenta) (Foram.mag.fwd + short anine teeth) T 5(Mammary lands) T 4 (mnion) T 3 (aired egs) T 2 (rd ppend. + Backbone) T 1 (Dorsal nerve cord + otochord) K TO MM: 1. hows...probable relationships 2. hows...probable sequence of origins 3. hows...shared derived characters K TO TO: (look for near vertical branches upwards from diagonal line on cladogram) guana-like animal: (branch from or near turtle line): guana is a reptile, like a turtle. at-like animal: (branch from or near hesus monkey): at is a placental mammal, like monkey. oldfish-like animal: (branch from or near Tuna line): oldfish is a fish, like the tuna. 6