Autumn.wmf (12088 bytes) Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;

Biogeochemical Cycles - Study Guide


Reading:  Purves et al.  Chapter 56

Goal and Objectives:  The major goal of this unit is to provide you with an understanding of the source, nature and mechanism of the movement of energy and nutrients in an ecosystem.  Specifically, upon completion of this unit you should be able to:

  1. describe the basic model for nutrient cycles

  2. outline the nutrient cycles of water, carbon, nitrogen, phosphorus

  3. explain the Gaia hypothesis


Important Terms/Concepts: (be able to use conversationally)

  • Abiotic

  • ammonia

  • ammonification

  • aquifer     

  • Atmospheric cycle

  • biogeochemical cycle

  • Biotic

  • denitrification

  • Gaia

  • Greenhouse effect

  • Hydrological cycle

  • Legume

  • mycorrhizae

  • nitrate

  • nitrification

  • nitrite

  • nitrogen fixation

  • Rhizobium

  • Sedimentary cycle

  • Slash and burn agriculture

Questions for Thought and Study:

  1. Trace the passage of a water molecule through the hydrological cycle

  2. Trace the passage of a carbon atom through the complete carbon cycle

  3. Trace the passage of a nitrogen atom through the complete nitrogen cycle

  4. Explain why nutrient cycles are termed "biogeochemical".

  5. Explain why legumes often grow in nutrient poor soil.

  6. Explain why legumes are sometimes called the "meat of the poor".

  7. For each biogeochemical cycle, indicate the importance of microorganisms

  8. Which nutrient cycle relies most heavily on microbes for its successful completion?

  9. For each nutrient cycle: (1) identify some uses for the element; (2)identify the major abiotic reservoir; (3) identify the major biotic reservoir; (4) identify the way and form in which the nutrient enters the biotic reservoir; and (5) identify the way and form in which the nutrient leaves the abiotic reservoir

  10. What is the Gaia hypothesis?

  11. Describe the experiment performed at Hubbard Brook. What did we learn from these studies?

  12. The data in the table below are extracted from work at Hubbard Brook.  What  conclusions can you draw from these data?

Data from Studies of Hubbard Brook, NH
















  1. Compare and contrast hydrologic, atmospheric and sedimentary cycles.  Identify elements characteristic of each.  Which is fastest? slowest?  Why? 

  2. What is the Greenhouse Effect?  Why is it occurring?  What will be the effects of global warming?  What is the role of carbon dioxide, CFC's, methane  and nitrous oxide in the Greenhouse effect?  What is the source of these materials? 

  3.  Trace the pathway that a (1) water molecule or (2) carbon atom in a sugar or (3) nitrogen atom in a protein, that is in my body (your brilliant instructor) would take to get into your body.  Assume that you aren't a cannibal. 

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Last updated: April 22, 2004        � Copyright by SG Saupe