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Web Exercises
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Project FeederWatch

The FeederWatch Program coordinated by the Cornell Laboratory of Ornithology is an excellent example of citizen science. Thousands of volunteers collect data on bird frequency and distribution from backyard feeders throughout winter months. The data are displayed on innovative animated maps that allow you to view dynamic information about a given species in a particular region or state over time. Go to: birds.cornell.edu/PFWMaproom/pfwmaproom.html to find a species and location that interests you; then consider the following questions:
    1. Does it surprise you that this species does or doesn't occur in your area?
    2. How would you account for the patterns you see on the map? Is it possible that the results show a bias in data collection rather than a real variation in distribution of the species?
    3. Some species display seasonal movements. Can you detect a pattern in changing distribution of the species you've chosen during the time shown? How would you account for the pattern (or the lack of a pattern) you observe?

Trophic Cascades in Aquatic Food Webs

Ecological relationships can affect physical qualities in our environment. To understand how this occurs, go to www.mhhe.com/environmentalscience. Click on the title of your textbook to take you to the Online Learning Center, and then click on the student edition. Click on "Regional Case Studies" on the left-hand navigational menu. Scroll down to the North region to find a case study titled "Food Web Control of Primary Production in Lakes." Read the text and study the graphics to answer the following questions.
    1. Explain the three graphs. Why does an increase in game fish (piscivores) cause a decrease in phytoplankton (algae) in a lake?
    2. If you were designing a test of this hypothesis, how would you regulate piscivore biomass experimentally?
    3. What would you use as a control in your study?
    4. What do the authors mean by top down and bottom up controls?
    5. Why do they call this a trophic cascade?

Alien Invaders: When Weeds Do Good and Bad Things

On the same regional perspectives page, look at the first case study in the Southwest Region. You can also find an interesting international case study about water hyacinth on the USGS Eros site at edcintl.cr.usgs.gov/waterhyacinth.html. Look at the Winam Gulf study for some impressive images of how this plant can clog lakes and waterways.
    1. When and why was water hyacinth introduced into the United States?
    2. Where did it come from?
    3. How fast does it spread?
    4. Why is it a problem?
    5. What possible benefits does it convey?
    6. How is it controlled?
    7. Drawing on what you’ve learned about community interactions in this chapter, why is this plant so aggressive and so successful in its new home?





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