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Homework/Test (ecosystems, food web, carbon cycle)

Objectives:  Discuss ecosystems, food chains, and carbon cycle

Question:  How does a change in one species of a food web change the carbon cycle?

Sub-objectives:  how small changes can have large impacts on the environment

Subtle Biotic Changes Have Big Environmental Impact

MADISON - By changing the composition of fish populations in a lake, scientists have found a switch by which the flow of carbon between lakes and the atmosphere can be turned on, off, reversed.                                                                                                                                                                            The finding is the first to show that only slight rearrangement of an intact ecosystem's FOOD WEB can directly influence the atmosphere.  The discovery is important because it demonstrates that single, seemingly subtle changes in ECOSYSTEM can have far-reaching consequences, and are capable of disrupting the fundamental biogeochemical processes of the Earth.  "Linkages in ecosystems are both stronger and stranger than we imagined," said Stephen R. Carpenter, a UW-Madison limnologist who, with fellow limnologists Daniel E. Schindler and James F. Kitchell, authored the report. "Biological processes have powerful feedbacks to processes that are normally thought to be purely physical or chemical in nature." While lakes occupy a very small area of the planet's surface, the discovery that simple biotic change is capable of altering the exchange of carbon between the atmosphere and the Earth's surface raises questions of global significance, said Carpenter.                                                                                                                                                                                                                                                                           "To what extent could fertilization of the oceans and alteration of oceanic food webs affect global CARBON CYCLE? In fact, runoff from land is now enriching coastal oceans to unprecedented levels, and industrial fishing is causing massive changes in marine food webs. So the global EXPERIMENT is underway," said Carpenter.                                            

Carbon, an essential nutrient in lakes, typically flows from the land in the form of dead leaves and other organic matter that accumulates and decays underwater. Usually, these processes lead to a surplus of carbon dioxide in lakes. Excess carbon in a lake is released as a gas, carbon dioxide, to the atmosphere. When there is a deficit of carbon dioxide, however, lakes draw the gas directly from the atmosphere.                                                                                        

Working on an isolated, undeveloped suite of lakes in Michigan's Upper Peninsula, the Wisconsin scientists were able to manipulate the flow of carbon between an entire, intact ecosystem and the atmosphere by placing either minnows or bass at the apex of the lake food web.  Bass, by preying on the minnows that consume algae-grazing zooplankton, effectively increased the flow of carbon to the atmosphere by freeing zooplankton from their PREDATORS. The booming zooplankton populations grazed the algae to the point where they were no longer a force to use the lake's excess carbon. The lakes, in effect, became pumps, expelling unused carbon to the air.                                                                                                                                                                            In lakes dominated by minnows, whose menus include algae-eating zooplankton, burgeoning algae populations and their photosynthetic requirements resulted in a carbon deficit, and the lakes become carbon sinks, drawing carbon directly from the atmosphere.  "This effect of fishes on gas exchange results from the changes in aquatic food webs that are regulated by the species of fish present in a particular lake," said Schindler.                                                                                                                  

 The changes in lakes, Schindler emphasized, will not have implications for global climate. However, the new understanding of the processes that alter the exchange of carbon dioxide between lakes and the atmosphere can be generalized to other ecosystems such as oceans.   "Although the consequences ... are much less known for marine systems than for lakes, we should expect that the ecological responses to exploitation are similar in many ways," Schindler said.

Instructions: Please number the lines in the article, highlight concepts and terms, and place notes along the margins. (5 pts.)

Questions

Please write answers except the multiple choice on a separate sheet of paper.

  1. Please define and use all underlined words in a sentence. (10 pts.) 

2.        Create a divided page graphic organizer study guide using the CAPITALIZED bold type words. (10 pts.) 

  1. What two fish were used in the experiment?  Circle the best answer.  Cite the sentence and paragraph in the article, or in the textbook, or other source. (10 pts.)
    1. sturgeon and bass
    2. bass and pickerel
    3. minnows and bass
    4. bass and sunfish
  2. What is an ecosystem?  Circle the best answer.  Cite the sentence and paragraph in the article, or in the textbook, or other source. (10 pts.)
    1. just another name for everything in the world
    2. living and dead things in a given area that interact together
    3. all the living things in an area
    4. all the organisms in an area that don’t interact
  1. What is the fundamental biogeochemical process (hint cycle) discussed in the article that is changed by the experiment with the different fish?  Circle the best answer.  Cite the sentence and paragraph in the article, or in the textbook, or other source. (10 pts.)
    1. nitrogen cycle
    2. carbon cycle
    3. oxygen cycle
    4. water cycle

       6.    Illustrate the carbon cycle.  (20 pts.)

       7.   Using  graphic organizers or concept maps illustrate the two different processes caused            by the introduction of the two different types of fish on carbon dioxide exchanges to the            lakes.  Include minnows, lakes, bass, zooplankton, algae-eating zooplankton, atmosphere,            algae, and carbon dioxide (not necessarily in this order). (25 pts.)

Extra Credit: (2 pts. each)

  1. What is“zooplankton”?
  2. What is a “limnologist”?
  3. What does the word “runoff” mean?

Research Question: List source (book, article, author, web page, etc.) (10 pts.)

1.        Research zooplankton and write an essay on them.  Explain the importance of zooplankton to life on Earth.