BOTANY 160                 PLANT ECOLOGY                FALL 1994

                              QUIZ I KEY

CHOOSE 5 of 8 (5 points each; Total 25 points)


1. Contrast collective and emergent properties and give an example 
   of each.


      Collective - properties of a community that are a composite 
                   (sum) of the lower levels of organization 
                   (individuals and populations). 

                   Examples: species diversity, community biomass 
                    and productivity.

      Emergent -   properties of a community that are a composite 
                   (sum) of the lower levels of organization 
                   (individuals and populations) and their
                   interactions.These properties appear only when
                   the community is the focus of attention.

                   Example: structure of the food web.

      [see your text - page 613]



2. (a) Write out the Beer-Lambert law.
   (b) What implications does the law have for phytoplankton 
       communities.


                       -kz
      (a)   I  =   I  e 
             z      0

          where:
                I  = light intensity at depth z,
                 z

                I  = light intensity at zero depth, 
                 0

                 e = base of natural logs, 
                 k = extinction coefficient and 
                 z = depth.

     (b) the exponential nature of light extinction means that 
         light energy is quickly absorbed with depth. Therefore 
         only the upper waters will have sufficient light for 
         phytoplankton growth.



3. What is the difference between resilience and resistance in 
   the context of ecosystem stability.


      - resilience refers to the ability of a community (or 
        ecosystem) to quickly recover from a disturbance.
      
      - resistance refers to the ability of a community (or 
        ecosystem) to maintain homeostasis in response to a 
        disturbance

      - these two concepts can be thought of as being inversely
        related.

     (extra credit for mentioning the time scale perspective 
      (ie generation times))



4. During the summer the vertical oxygen profile of an 
   oligotrophic lake is the opposite of a eutrophic lake. 
   Why is this so?


      The oxygen profile of an oligotrophic lake increases with 
      depth because deeper water is colder (can hold more 
      dissolved O2) and there is little decomposition occurring 
      to consume the O2. During the summer the eutrophic lake has 
      less dissolved O2 with depth (despite the colder water) 
      because appreciable decomposition is occurring in the 
      hypolimnion and consuming much of the O2.



5. What are three ways in which phytoplankton remain in the 
   trophogenic layer of a lake.


      1) motility (flagellated cells)

      2) morphology (form resistance to sinking)

      3) storage of low density reserves (ie. diatoms store oil)

      4) gas vacuoles (blue-green algae)



6. Diagram and label the vertical and horizontal zonation of a 
   lake. Indicate the type of communities you would find in 
   each zone.

       ---------------------------------------------------->
      LIMNETIC                                 LITTORAL
                                                 [macrophytes,
                                                  periphyton]  
       [plankton]                                                 _____
      ~^~^~^~^~^~^~^~^~^~^~^~^~~^~~~^~~~~^~~~^~^~~~~^~^_^.^.^----' 
      |                                         ...--'
      | EUPHOTIC (Trophogenic)               .-'
      |  [phytoplankton,autotrophs]        .'
     .|. . . . . . . . . . . . . . . . .  /
      |                                 .'
      |                                /
      | APHOTIC (Tropholytic)        ./
      |                             /
      |                            /
      |                         .-'	
      |                     _.-'
      V BENTHOS      _...-''
     --------------''
   [decomposers, heterotrophs]  


7. Briefly summarize the essence of the message that O'Brien 
   is sending in his paper on Mirror Lake.


      Ecologists must always be aware of the scale (both 
      temporal and spatial) of the part of the community 
      or ecosystem that they are investigating. In particular 
      they must understand the scale at which they are 
      collecting their data relative to the organisms they are 
      studying and the research questions they are asking.



8. Name and define two unique properties of water that have had 
   major influences on the structure and function of aquatic 
   plant communities.


      1) viscosity - water is 'sticky' or viscous due to the 
                     polarity of the molecules and hydrogen 
                     bonding. One result is that frictional   
                     resistance of a particle moving through 
                     water is 100 times that of air.

      2) heat capacity - water is capable of storing large 
                     quantities of heat with a relatively 
                     small rise in temperature.

      3) light extinction - water absorbs certain wavelengths 
                     of light energy more so than others. This 
                     phenomenon is exponential in nature and 
                     restricts photosynthetic autotrophs to the 
                     upper layers of water.