ECOLOGY QUESTION 1986:			L. PETERSON/AP BIOLOGY

	Describe the biogeochemical cycles of carbon and nitrogen. Trace these
	elements from the point of their release from a decaying animal to their 
	incorporation into a living animal.

  
  STANDARDS:
  
  The question was divided into two sections for grading, with a maximum number of points of 8 per
  section. For each maximum assigned, there were more points possible 
  to allow the student several ways to reach the maximum.
  
  For the CARBON CYCLE, it was possible to earn points for each of the following statements or
  ideas:
  __  Explanation of the role of green plants as producers
  __  Mention of herbivores in a way that indicated an understanding of their role 
  __  An indication that carnivores obtained C from herbivores
  __  Discussion of the role of decomposers in returning C to the atmosphere as CO2
  __  Mention of CO2 production via respiration of green plants, herbivores or carnivores
  __  Discussion of the C in oil, natural gas, and coal as originating from the remains of 
         organisms
  __  Mention of CO2 release to the atmosphere through the burning of fuel or through 
         release of C from limestone.
  __  Discussion of the existence of dissolved CO2 in the bodies of water on the earth.
  __   An indication that human activity had a significant impact on the carbon cycle.
  
  In the case of the nitrogen cycle, there were 14 possible points from which it was possible for the
  student to earn the maximum of 8 for that portion of the questions. 
  __  An indication that organic molecules were broken down to amino acids after death
  __  Discussion of deamination
  __  Mention of NH4+ as the product of deamination
  __  Indication that ammonium ion can be converted to nitrate (a second point if there is 
         inclusion of the further oxidation to nitrate)
  __  Discussion of denitrification
  __  Mentioning the role of microbes, industry, or lightning in affecting atmospheric 
         nitrogen.
  __  Understanding that when nitrogen gas is fixed, it is converted to the ammonium ion.
  __  Indication that nitrate or nitrite or ammonium ions can be taken up by organisms
  __  Mention of nitrogen loss to living organisms which results from burning or leaching
  __  Indication that plants use absorbed nitrogen to make proteins
  __  An understanding of the conversion by animals of plant proteins into animal proteins
  __  Indication that on death or in excretion organic nitrogen is released into the 
         environment.
  __  Indication of a significant impact of human activity on the nitrogen cycle.