SHW - Pg. 8

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CH. 53: COMMUNITY ECOLOGY

1. How is co-evolution significant in community ecology?
- coevolution describes interactions involving reciprocal evolutionary aadaptations in two species: A change in one species acts as a selective force on another species, and counter adaptation by the second species, in turn, is a selective force on individuals in the first species.

2. Fill in the chart of interspecific interactions.

Interaction
Effects on Population Density
Example

Competition
A -/0 interaction between similar species in which a species compete for resources.
Ex. Lions fighting over territory or mate

Predation
(includes parasitim)
A +/- interaction between species in which one species, the predator, kills and eats the prey
Ex. a lion attacking and eating an antelope

Mutualism
An interspecific symbiosis in which two species benefit from their interaction (+/+).
Ex. nitrogen fixation by bacteria in the root nodules of legumes

Commensalism
An interaction that benefits one species but neither harms nor helps the other (+/0).
Ex. barnacles that attach to whales


3. What is the competitive exclusion principle?
- The concept that when the populations of two species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population.

4. Describe Gausse’s experiment with Paramecia.
- In this experiment Gausse grew two different Paramecium separately with constant amounts of bacteria added daily for food, populations of the species P. Aurelia and P. caudatum each grow to carrying capacity. But when the two species are grown together, P. Aurelia has a competitive edge in obtaining food, and P. caudatum is driven to extinction.

5. Define ecological niche.
- The sum total of an organism’s utilization of the biotic and abiotic resources of its environment.