Q1. A researcher studying the deciduous forest outside Fremont has made an alarming discovery. While taking an inventory of the species present on the forest floor, Professor Peter Tate discovered many earthworms of an Asian species not previously know to live in the area. The Asian worms, unlike native worms, have voracious appetites. The forest floor is home to a myriad of species that live in the leaf litter, which is composed of several years' accumulation of slowly decomposing leaves. Dr. Tate explained, "the leaf litter is critical to the survival of local species of forest plants". Dr. Tate has found the Asian worms, unlike their indigenous cousins, consume the entire layer of leaf litter in a single season. He said, "This sets the stage for the takeover by invasive exotics such as Japanese stilt grass." Dr. Tate and other scientists are exploring strategies for the control of the Asian worms.

• Support Dr. Tate's assertion that "the leaf litter is critical to the survival of local species of forest plants." Include in your discussion the roles of leaf litter in a deciduous forest ecosystem.
• Describe 3 abiotic changes that would be likely to result if the exotic worms consumed all the leaf litter in a single year.
• For one of the changes you identified in part b., explain how the change could set the stage for the takeover of Japanese stilt grass or other exotic species.
• Design a controlled experiment to determine whether the worms, in fact, do change the forest ecosystem. Identify the environmental factor you will measure, and include the specific hypothesis you will test and the data you will collect.

Q2. Species such as the dusky seaside sparrow, the passenger pigeon, and the woolly mammoth are extinct. Populations of other species have declined to the point where they are designated as threatened or endangered.

1. Identify one threatened or endangered species and explain why its population has declined.

2. Describe three characteristics of organisms that would make them particularly vulnerable to extinction.

3. Present three arguments in favor of the maintenance of biodiversity.

4. Name and describe one United States federal law or one international treaty that is intended to prevent the extinction of species.

Q3. For decades, forest fires in the United States have been suppressed. In 2003 legislation was passed under the Healthy Forests Initiative (HFI) in response to the record-breaking wildfires that had occurred in the early 2000s. Some environmental and conservation groups fear that negative impacts could result if timber companies are encouraged to harvest medium- and large-size trees in federally owned forests while clearing away the smaller trees and underbrush.

1. Identify TWO characteristics of forests that develop when fires are suppressed, and explain why the practice of fire suppression does not reduce, but actually increases, the risk of intense and extensive forest fires.

2. The effects of the HFI are expected to extend beyond fire reduction. Excluding fire reduction, describe ONE positive and ONE negative effect likely to result from the implementation of the provisions of the HFI.

3. Describe TWO ecosystem services provided for humans by forests. Explain how clear-cutting would affect each ecosystem service you describe.

4. Identify a specific type of plant community or biome (other than a forest) that is naturally maintained by fire. Explain how the fire maintains the community or biome.

Q4. The graph above shows the decline in the catch of ground fish (such as cod, haddock, and flounder) from Georges Bank from 1965 to 1995. This decline in the fish harvest resulted in the closure of large portions of the fishery.

1. Identify the five-year period during which the greatest rate of decline in the fish harvest took place. For that five-year period, calculate the rate of decline in the fish harvest, in metric tons per year. Show clearly how you determined your answer.

2. Choose any TWO commercial fishing practices from the list below. For each of your choices, describe the practice and explain the role it plays in the depletion of marine organisms.

• Bottom trawling
• Long-line fishing
• Using drift nets/gill nets/purse seines
• Using sonar

3. Identify one international regulation or United States federal law that applies to the harvesting of marine food resources and explain how that regulation or law helps to manage marine species.

4. The oceans of the world are often referred to as a commons. Give an example of one other such commons, explain how human activities affect that commons, and suggest one practical method for managing that commons.

Q5. Define ecology.

Explain the roles that organisms, communities, and populations play in the functioning of an ecosystem.

Explain the flow of energy through an ecosystem using the laws of thermodynamics, food webs, food chains, and eco-pyramids.

Explain the process of ecological succession in ecosystems.