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;;

Community Questions 

Resource Partitioning in Ungulates in the Serengeti
            Zebra, wildebeest and Thompson�s gazelles live on the Serengeti.  At first glance they appear to violate the principle of competitive exclusion (one species per niche).  However, they separate their niches and minimize competition by feeding in sequence.  Zebras typically eat long stems, wildebeest follow and eat shorter side shoots while the gazelles go after vegetation near the ground.  Plot a resource utilization curve (% of diet vs. stem height) that represents the realized niche for these three species.  Now, assume that zebras cannot eat short shoots, gazelles cannot eat long shoots but wildbeests can eat any size.  Now, plot the theoretical niche for these species.

Predator/Prey Relations
     Prey species rely on a variety of defenses to avoid becoming dinner.  These include:

    Can you give an example of each?

Everything is connected to everything else
.  Biologists have always appreciated this �law.� Clearly a chain is only as strong as its strongest link.  Break one link and the remainder of the chain falls apart.  However, what we didn�t realize until relatively recently is that even if you break a link at the end of the chain it can have serious impact on the community.  Give an example of top-down control where a top level predator affects the community.

Symbiotic Relations
� Consider the interaction between two species.  (a)  Fill in the blanks in the table with the following terms - mutualism, commensalism, amensalism, parasitism.   (b)  Give an example of each.



Species 1





not affected

Species 2









not affected





Succession Table:   Complete the following table. 


Early Successional Community

Late Successional Community

Organismal Size (small vs. large)



Niche (broad & general vs. narrow & specialized)



Life cycle (long vs. short)



Selective Strategy (r vs. K)



Reproductive Strategy (quality vs. quantity)



Nutrient Cycles (open & rapid; closed and slow)



Diversity (low vs. high)



Stability to disturbance (good vs. poor)



% soil moisture (low vs. high)



light penetration to ground (high vs. low)







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Last updated: April 23, 2004        � Copyright by SG Saupe