1. ecology: ecosystems (1/2 page) - choose one of these:
a. choose two of the biomes from the weeks 3-4 notes outline. describe the abiotic and
biotic factors that determine ecosystem structure of each biome. then explain the
specific major impacts of human activities on each biome, and how we can reduce these
impacts.
b. describe two ecosystem functions that are important for human existence and economy.
for each function, explain how human activities have impacted the ability of the
ecosystem to provide this function, and how we can reduce these impacts.
2. ecology: species interactions (~1/2 page) - choose one of these:
a. describe the competitive exclusion principle in your own words. how does competitive
exclusion determine the niches of different species in a community? give an example to
support your answer.

Juan and carol were studying invertebrates in biology. they knew that segmented or earth worms preferred a dark, moist habitat. during this lab, they would be investigating the responses of organisms called planaria or dugesia tigrina. these were simple flatworms that still had a one-way digestive system and a very simple nervous system. juan and carol placed the planaria in a petri dish containing cool, distilled water that was partially covered with black paper. they shined a light on the dish. next, they removed the paper and placed a small amount of chicken liver at one end of the dish. they added a few large salt crystals to the water. finally, they added drops of hot water to the cool water in the petri dish. their results can be seen in the data table. according to their experiment, all but one conclusion is valid.