DO PANDAS REALLY EXIST? TEACHER HANDOUT Grade Level: High-school biology Objectives: The students will: Become familiar with the current uncertainty regarding the relatedness of the raccoons, pandas, and bears. Understand that scientific interpretations change as new data become available. Evaluate three proposed phylogenetic trees that show the relatedness between the raccoons, pandas, and bears. Use biogeographical, behavioral, morphological, and molecular data to evaluate the possible phylogenetic reconstructions. Outline the steps of how the pandas thumb (enlarged sesamoid bone) may have evolved. Background Information: The students should already be familiar with the following topics: Phylogenetic trees DNA structure The steps of acquiring adaptations (natural selection) Time Requirement: (Includes time for a short introduction to the panda species and a followup discussion) Two 70-minute blocks or three 45-minute class periods Teacher Preparation: Make copies of the 2 handouts. Materials (one per student): Student handout - Do Pandas Really Exist? Student handout Background information on the question: Do Pandas Really Exist? Evaluation: Answers on student handout, even if technically incorrect, should be defensible. Check for understanding during classroom discussion.
DO PANDAS REALLY EXIST? TEACHER HANDOUT 1. What question were scientists trying to answer? Scientists were trying to determine if pandas are more closely related to the bears or the raccoons. 2. Below are the three possible phylogenetic trees that scientists have proposed for the raccoons, bears, and pandas. A phylogenetic tree shows how closely different species are related to each other. The closer two branches are to each other on the tree, the more closely the species are related to each other. For example, all three of these trees show that the raccoon (Procyon lotor) is very closely related to the coatimundi (Nasua nasua), which are both members of the raccoon family (procyonidae). a. According to these phylogenetic trees, what other two species are closely related to each other? The grizzly bear and sun bear. b. To which family do these two species belong? Ursidae c. According to the background information (in Do Pandas Really Exist? ), fill in the option numbers for each of the phylogenetic trees. d. According to the background information on each of the proposed relationships, fill in the red panda and the giant panda on the phylogenetic trees. Option # 3 Procyon lotor Nasua nasua Red panda Giant panda Ursus arctos Ursus malayanus Option # 1 Procyon lotor Nasua nasua Red panda Giant panda Ursus arctos Ursus malayanus Option # 2 Procyon lotor Nasua nasua Red panda Ursus arctos Ursus malayanus Giant panda 3. Look at the biogeographical information that has been provided. a. Which option (1, 2, or 3) does this information support? 3 b. Explain your answer. Both pandas live near each other in Asia, but neither live near the raccoon family. 4. Look at the fossil information that has been provided. If raccoons first appeared in North America some 20 million years ago, and the red panda is a descendant of these original raccoons, how could they have ended up in China? (Hint: look at the map that shows how the continents have moved over time.) They may have lived near each other, at one time, but the continents have moved and could have split their descendents apart. 5. Read the behavioral information that has been provided. a. Which option (1, 2, or 3) does this information support? 3 b. Explain your answer. Both pandas eat bamboo (bears do not do this) and both mark their territory using scent glands (bears do not do this either).
6. Look at the information that has been provided about the size of the animals in Table 1. a. Which option (1, 2, or 3) does this information support? 2 b. Explain your answer. The red panda has a weight and skull length within the range of the procyonids and the giant panda has a weight and skull length within the range of the ursids. However, both species of panda give birth to very small offspring. 7. Table 1 includes the dental formulas for each species. A dental formula shows how many of each type of tooth a species has on one half of the mouth (I = incisor, C = canine, P = premolar, and M = molar). The number in the numerator is how many they have in the upper jaw, and the number in the denominator is how many they have in the lower jaw. The number after the = is the total number of teeth the animal has. For example, the in just the left or right side of their mouth the raccoon (Procyon lotor) has 3 incisors in the upper and 3 in the lower jaw, 1 canine in the upper and 1 in the lower jaw, 4 premolars in the upper and 4 in the lower jaw, and 2 molars in the upper and 2 in the lower jaw. If you add all of these up and multiply by 2, you will see that the raccoon has a total of 40 teeth. a. Which option (1, 2, or 3) is supported by the dental formulas? 2 b. Explain your answer. The dental formula of the giant panda is the same as those of the bears. The red panda has a dental formula that is different than the others, but is most similar to the procyonidae. The procyonids have two more upper premolars than do the red pandas. Otherwise, they are identical. 8. It is very difficult for a large animal like the giant panda to get enough calories from eating bamboo shoots. Yet, they manage to do it with the help of their thumb (see Figures 11 and 12). Fill in the table below to explain how the giant panda ended up with this interesting adaptation. Be sure to use the word sesamoid bone in your answer. Steps to getting adaptation 1. Organisms produce more offspring than can survive to reproduce. The panda s thumb Giant pandas produce more offspring than can survive to reproduce. 2. Offspring vary, and some of the Because of genetic differences, some giant pandas variation is due to genetic differences. have sesamoid bones that are longer than others. 3. Selective pressures are present. They are faced with the selective pressure of getting enough calories from the bamboo. 4. Organisms with beneficial heritable Pandas with longer sesamoid bones are better able variations are more likely to survive, to strip the leaves off of the bamboo and get reproduce, and pass the trait on to calories more efficiently than the others. This makes offspring. them more likely to survive, reproduce, and pass the trait on to their offspring. 9. Now let s summarize the conclusions you have drawn so far. a. Place a checkmark beneath the option # that is best supported by the evidence. b. Add up the total number of checkmarks in each column and write them down as totals. Type of evidence Biogeography Behavior Diet Size Dental Option 1 Option 2 Option 3 c. Based on your evidence so far, how do you think the two panda species are related to the raccoon and Formula Total = 2 3 bear families? So far, it seems as thought the two pandas are most closely related to each other.
DNA Evidence. In the 1980s and 1990s scientists compared the DNA of various raccoons, bears, and pandas. By looking at a particular sequence of nucleotide bases (A, T, C, and G) they were able to compare their similarities and differences across species. The idea is that the more similar the DNA sequences are to each other, the more closely related the species are. Also, the more different the DNA sequences between species, the more distantly related the species are. Below is a representation of what they found: Species DNA Sequence Raccoon (Procyon lotor) A A A T A A G A A T A T A T A C C A C G Coatimundi (Nasua C A G T A A G A A T A T A T A C C A C G nasua) Grizzly Bear (Ursus C T G T A C C A T A C C A T A C C C C C arctos) Sun Bear (Ursos C A G T A C C A T A C C A T A C C C C C malayanus) Red Panda (Ailurus C A G T A C C A A T A T A T A C C A C G fulgens) Giant Panda (Ailuropoda melanoleuca) C A G T A C C A T A C C A T A C C A C G 10. Look at the DNA sequences above (it is helpful if you have an extra copy that you can cut out). Figure out how many nucleotide base differences there are between all of the combination of different species and fill in the table below. Fill in the number of nucleotide base differences between each pair of species. Teachers, please note that the DNA sequences have been fabricated. However, they do reflect the relationships provided by molecular data. Raccoon Coatimundi Grizzly Bear Sun Bear Red Panda Giant Panda Raccoon (Procyon lotor) ---- 2 11 10 4 8 Coatimundi (Nasua nasua) ---- 9 8 2 6 Grizzly Bear (Ursus arctos) ---- 1 7 3 Sun Bear (Ursos malayanus) ---- 5 2 Red Panda (Ailurus fulgens) ---- 4 Giant Panda (Ailuropoda melanoleuca) ---- 11. DNA evidence. a. Which option (1, 2, or 3) does the DNA evidence support? 2 b. Explain your answer. The DNA of the red panda is most similar to the procyonids and the DNA of the giant panda is most similar to the bears. 12. How did the DNA sequences become different from each other in the first place? Mutation 13. Like DNA, proteins can also be compared to determine relatedness. a. Explain how you think scientists could compare proteins of different species. Answers may vary but may include amino acid sequences, how big the proteins are, etc. 14. What other information would have been helpful to you in this investigation? Answers may vary but may include information on more bear and raccoon species, actual fossil information, etc.
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