Name the disturbance and a potential risk of this disturbance on the native community.

1. According to the competitive exclusion principle, what outcome is expected when two species with identical niches compete for a resource? • Based on your answer above. If a new species is introduced to an area that have the same niche as an other native species that already is living in the area, who would have an advantage and why? • Consider a grassland with five trophic levels: grasses, mice, snakes, raccoons, bobcats. How would plant biomass change if the bottom-up model applied? If the top-down model applied? Explain.

2. Most prairies experience regular fires, typically every few years. These disturbances tend to be relatively modest. How would the species diversity of a prairie likely be affected if no burning occurred for 100 years. Explain. • An important species in the Chesapeake Bay is the blue crab. It is an omnivore, eating eelgrass and other primary producers as well as clams. It is also a cannibal. Humans and sea turtles eat blue crabs. • Draw a food web that includes the information above. • Assuming the top-down model for this system, describe what would happen to the abundance of eelgrass if humans stopped eating blue crab.

3. Understanding problems in community ecology often requires the integration of a number of ecological principles. Explain the following by using as many learned principles as you can. • A small clan of hyenas killed an antelope. While they were feeding on the carcass, two female lions approached and chased them away from the carcass. • The Hawaiian woodpecker has a distinctive beak that is used as a tool. Males have larger beaks and they peck on tree trunks, while females peck on branches and twigs. They have the lowest reproduction rate among all small birds (1 chick/year). But they care for their young. The decline of their numbers corresponds with the introduction of rats, cats and logging in the island.

4. Australia and New Zealand are home to a wide variety of marsupials. Until colonization by foreign traders, placental mammals were not found in these areas. Following colonization, rabbits were introduced to the area. • Name the disturbance and a potential risk of this disturbance on the native community. • Predict how the introduction of rabbits changed the community • Design an experiment to test your hypothesis. • What would you expect to find if your hypothesis is correct? What would you expect to find if your hypothesis is not correct?