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STANDARD V: Objective 1 Title: The Evolution of Canis pedatus Background Knowledge: Students need no prior knowledge. This is an introductory activity. Objective: Students will evaluate an isolated population and infer the effects of natural selection and reproductive isolation. They will identify environmental forces that drive evolution. They will also investigate the definition of a species. Equipment and Supplies: colored pencils, unlined paper Safety Issues: None Duration: Two 50 minute class periods with optional 3rd class period for presentation of results Procedures for Teachers: 1. 2. 3. 4. 5. 6. Make a copy of student sheet Divide students into groups of 4 Assign each group an island Read through activity with students and answer any questions Allow students 2 full class periods to work on this assignment You many want to have students present their work to the class in a 3 rd class period Answers to Questions: 1. 2. 3. 4. 5. Answers will vary. Answers will vary. Answers will vary. Answers will vary. Because the animals were placed in very different environments and allowed to roam free for an extended period of time this most likely would lead to the formation of four different species. If the species from each island were introduced to each other again they probably would not interbreed. There may be physical, social or even genetic barriers that prevent them from producing fertile offspring. 6. The larger the dog population the more genetic variability is present. The larger the gene pool the more likely the species is to survive in its new habitat. This is because there is a larger number of alleles in the population and more chance of some being beneficial. If the population was small it wouldn’t be likely to survive the environmental pressures of the new environment. 7. Selective breeding is a controlled change in a population. A person selects for a desired trait and then breeds those organisms which possess that trait so that the presence of the trait increases in future generations. This happens independent of the environment. Natural selection is driven by pressures in the environment which make some individuals better fit and more likely to survive and pass on their genes to future generations, thus increasing the frequency of the beneficial trait in the species. 8. Mutation provides the raw material for evolution. Without mutation evolution could not occur. Usually mutations are harmful but some are beneficial and can make an organism better adapted for its environment. Recombination allows for increased diversity in the gene pool as opposed to asexual reproduction. This again allows for more chances that organisms may be better fit for their environment. 9. If the population were an asexually reproducing population then it would reproduce much faster. However if the bacteria was not well suited for the environment it may die out very quickly because there is not a great deal of diversity in the gene pool. Without this diversity it makes adaptation difficult. 10. Answers will vary. Scoring Guide: Questions are valued at 5 points each for a total of 50 points. You may also want to include a group participation grade of 15 points. Student Sheet The Evolution of Canis pedatus Name:__________________________________________________ Period:_______________ Introduction: In this activity you will imagine that 800 years ago an international expedition discovered a previously unknown dog-like creature. The expedition's leaders, all from different Islands of the world, each took several hundred of the species on board their vessels and returned to their own lands. The animals were originally held in captivity and allowed to mate randomly. Their numbers increased and eventually most of them were set free to roam. You are to decide if the animals could have survived in their new habitat and then, if they had survived, how the animals could have changed over 8 centuries as they adapted to their new environments. Objectives: The purpose of this activity is to decide: If a population of the species Canis pedatus would survive being relocated to a new environment; If the species Canis pedatus would show adaptations to its new environment over a period of four hundred years; Whether the animals with those adaptations still belong to the species Canis pedatus. Background information on the species Canis pedatus: Height: medium, similar to a spaniel Hair: medium length, brown, white, black mix Tail: bushy, hangs down to its heels Snout: long, similar to a collie, with medium-sized teeth Ears: short and pointed Feet: unusually large, with small sharp claws Poor night vision Moderate runner: runs at speed of the average house cat Omnivorous, but has a particular liking for small birds Environments: Island A The island is fairly flat, with an occasional hill. The ground is soft dirt, and several species of shrubs grow towards the center of the island. There is no animal life on land, but the water is teaming with fish. The island is surrounded by a coral reef, which keeps the predators out. The shore is sandy with no algal growth. Fresh water is available. Island B The island has a rocky shoreline. Numerous tide pools dot the island along the shore where the wave action is somewhat sheltered by rock outcrops. The tide pools host barnacles, abalone, sea urchins and crabs. Algae grows all around the island; however, it is quite sparse in the tide pools where the various animals feed. The current is quite strong along the rocky outcrops where the algae grows best. Fresh water is available. Island C The island is somewhat barren. A few species of cactus thrive on the bare rocks. A large cactuseating tortoise inhabits the island. A species of very large bird nest on the island annually. They build their nests on the rocks, and protect their eggs from the sun by standing over the nests with outspread wings. The nests are always found on the windy side of the island which is somewhat cooled by offshore breezes. Island D The island is an extinct volcano. Vegetation on the island changes with the altitude moving up the volcano. Grasses grow at the base. Further up the slope the grasses give way to low shrubs. Half way up, the island becomes quite lush; tropical plants and trees dominate the landscape. At this altitude, the island experiences frequent rain showers. There are two species of birds that inhabit the island. One is a raptor, which preys upon the smaller birds. The other fishes the waters approximately one mile offshore. Both nest in trees. Procedures: You will be assigned to groups and each group will be given a letter that corresponds to an environment. As a group you must complete the following tasks and questions. 1. As a group, decide if the species could have survived after being allowed to roam in the wild, given their characteristics and lifestyle. Explain your decision. 2. Examine the traits the dog population began with. Describe how each trait might be influenced by natural selection and the environmental factors that provided the pressure for change. Record every change that could have occurred, together with a statement to explain the functional benefit of the change. 3. Provide a written description of the animal and its lifestyle. Include a food web, a discussion of energy use and conservation, nocturnal or diurnal, habitat etc. 4. Include a colored sketch that shows your "new and improved" appearance for this animal. The animal should appear in its ecosystem. 5. Briefly look at the descriptions of the other habitats. The dogs began as a single species but they were then reproductively isolated. What effect do you think this had on the individual populations on each island after 800 years. 6. Explain how the adaptations and evolution of this species is influenced by the number of dogs that were introduced to the island. In other words, how does genetic variation affect a species ability to adapt to a changing environment? 7. How are the forces of natural selection different than selective breeding of dogs and the practices used in agriculture? 8. What role does mutation and recombination play in the evolution of this species? 9. How would the evolution differ if this were an asexually reproducing bacteria instead of a sexually reproducing mammal? 10. Is this modern animal still a Canis pedatus? Defend your answer based on the definitions of a species.