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Rat Islands: An Exploration in Speciation Background: After many years of studying nature and observing animals and their traits, Charles Darwin came up with his theory of evolution. In 1838, the idea came to him that organisms with favorable variations would be better able to survive and to reproduce than organisms with unfavorable variations. He called this process Natural Selection, because nature "selects" the survivors. The results of natural selection would be evolution. Darwin published a book in 1859, On the Origin of Species by Means of Natural Selection. Darwin's book was supported by many examples. The six main points of his theory are as follows: 1. Overproduction – Most species produce too many offspring than needed to maintain a population but only a small fraction of those offspring live. 2. Competition – Offspring must compete against one another for food and shelter, only a small fraction will survive long enough to reproduce. 3. Variation – Some characteristics of species are different (variation). These characteristics are vital in the survival of the individual. Some may affect the ability to get food, run faster, escape enemies or find a mate. 4. Adaptations – Because of variations, some individuals may be better adapted to reproduce and survive than others. An adaptation is an inherited trait that improves the organism's chances of survival and reproduction. 5. Natural Selection – The environment selects plants and animals to be the parents of the upcoming generations. They must have desirable traits in order to survive. Those offspring better adapted to survive in their environment will pass those traits on to their offspring. 6. Speciation – Over many generations, favorable traits accumulate in species and form new species. The formation of a new species is called speciation. Introduction: A ship, infested with black rats (Ratus rattus) as many ships are, has hit a submerged rock and is starting to sink. While the people have lifeboats to escape onto, and will be rescued by the Coast Guard, the rats aboard are not so lucky, they have to swim to shore to survive. There are 4 nearby tropical islands which the rats can reach before they drown or get eaten by hungry predators, but these rats are not well adapted to survive on these islands. They do, however, have good senses of hearing, sight, and smell, and can eat a wide variety of food; not to mention that rats are highly intelligent. Random mutation and natural selection will allow the rats to evolve into a new species that is adapted to survival on the island. Assignment: Knowing what you do now about evolution and Darwin's theory of natural selection, your job is to design a rat which has adapted to the conditions of the island you were assigned. Adaptations can be structural (to the body itself), physiological (to the body processes or proteins and enzymes the body produces), or behavioral. Think about the build and anatomy of a normal rat then give your rat the necessary variations and adaptions to survive the environment of this new island. Be ready to share your rat and its environment to the class; your presentation should include the following: 1. Following the engineering design process, develop your new species of rat 2. Draw your island, and your rat with its adaptations 3. Complete the table that lists your rat’s adaptations, their origins (what structures they arose from) and explain how each adaption allows the rat to survive 4. Calculate the proportion in size between your new rat and a common rat 5. Present your rat to the class ISLAND A: The island is fairly flat, with an occasional hill. The ground consists of soft dirt. Several species of shrubs grow toward the center of the island. There is no animal life on land, but the water is full of friendly fish that swim around the island. The island is also surrounded by a coral reef which keeps 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, chitons, abalone, sea urchins and crabs. Algae grow 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 grow best. Freshwater 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 nests on the island annually. They build their nests in 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 inactive volcano. Vegetation in 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 raptor and the other is a small finch. The raptor enjoys eating small rats. Table 1: Rat Adaptations and their Benefits Adaptations for Island ____ Adaptation Derived From Type: S, P, or B Survival Benefit