BOTANY 160                 PLANT ECOLOGY                FALL 1994

                              QUIZ II KEY  


1. THE EXPONENTIAL GROWTH EQUATION CAN BE EXPRESSED AS
                                               rt
          dN/dt = rN  or equivalently, N  = N e
                                        t    0
 (a) MODIFY THE ABOVE EQUATION TO TAKE INTO ACCOUNT THE NEGATIVE
FEEDBACK OF POPULATION DENSITY ON GROWTH RATE (HINT: THE LOGISTIC
EQUATION DOES THIS).



          dN/dt = rN((K-N)/K)



 (b) WHEN MODELLING A POPULATION'S GROWTH WITH THIS EQUATION
SEVERAL SIMPLIFYING ASSUMPTIONS ARE MADE. LIST TWO OF THEM.

          - the population is homogeneous (no age or spatial      
             structure)
          - generations overlap (reproduction is continuous and   
             therefore population increase is instantaneous)



2. WHAT ARE THE TWO PROBLEMS UNIQUE TO PLANT POPULATIONS THAT ONE
FACES IN CONDUCTING DEMOGRAPHIC STUDIES? 

          - plants are modular
          - stage is generally more important than age
          - many plants have indeterminate growth
          - seed dormancy (timing of germination unrelated to     
            timing of reproduction)


3. HOW DOES THE RELAY FLORISTIC MODEL OF SUCCESSION DIFFER FROM
THE INITIAL FLORISTIC COMPOSITION MODEL OF SUCCESSION?

          The relay floristics model states that each seral stage
          facilitates its own replacement by altering the         
          environment and making it more conducive to the next    
          sere.

          The initial floristic composition model states that     
          representative species of all seral stages are present  
          initially and that eventually the late successional       
          species replace the early successional species.


4. HOW DOES A DYNAMIC LIFE TABLE DIFFER FROM STATIC LIFE TABLE?

          A dynamic life table shows the fate of a cohort from    
          birth to the death of the last individual.

          A static life table is constructed from age-structure   
          data from just one time interval. Survivorship and      
          therefore age structure of earlier age intervals is     
          inferred (back extrapolated) from the one time          
          interval.



5. ONE ATTRIBUTE OF A POPULATION THAT CAN BE CALCULATED FROM A
LIFE TABLE IS THE BASIC REPRODUCTIVE RATE (R0). (a) WHAT IS IT?
(b) HOW IS IT CALCULATED?
   

          (a) the rate at which the population is growing 
              (either +, - or 0)
   

          (b) N    /N   or (Sum) l  m
               t+1   t            x  x


6. (a) WHAT IS MEANT BY LIFE HISTORY?

          The combination of attributes that defines a species    
          growth and reproduction pattern  (growth, size,         
          storage, reproduction (when, how often)


   (b) WHAT PARTICULAR ASPECT OF LIFE HISTORY IS SELECTED FOR IN  
       A GIVEN HABITAT?

          Total reproductive value = realized + residual


7. LIST TWO ASPECTS OF THE LIFE HISTORIES OF R AND K SELECTED
SPECIES THAT YOU WOULD EXPECT TO BE DIFFERENT.

             r Selected                     K selected

           - many offspring               - few offspring
           - early reproduction           - late reproduction
           - reproduces once              - reproduces many times
           - small size                   - large size
           - larger % of resources        - smaller % of          
             invested in reproduction       resources invested    
                                            in reproduction
                      


8. WHAT THREE THINGS NEED TO BE QUANTIFIED ABOUT A SITE IN ORDER
TO ADEQUATELY DESCRIBE THE LIGHT ENVIRONMENT OF PLANTS LIVING AT
THAT SITE?

          - light intensity
          - light quality
          - light duration