RAT ISLANDS: An Exploration in Speciation
This activity allows students to use some of their creativity to imagine how rats would adapt to a particular island in order to survive. You can make up a story as elaborate as you want to explain how the rats ended up on their Island (A, B, C or D) and how long they have been on the island in order to change so much.
Each group gets an island and must design a rat which has adapted to the conditions of the island. I have the students draw island, the rat with its adaptions and explain how each adaption allows the rat to survive. You could then have the groups present their rats. It is interesting to see how different the rats are even with the same island conditions.
Give each group one of the following islands:
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.
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 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.
The island is somewhat barren. A few species of cactus thrive on the bare rocks. A large cactus-eating 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.
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.