1. Community Ecology

2. Community Characteristics
Diversity – number and abundance of species
Interspecific interactions
Stability - ability to recover from disturbance

3. Diversity Species diversity has 2 parts
Number of species
Abundance of each one (usually expressed as density)
Genetic diversity – how similar a population of organisms are to each other, important for long-term adaptations to changes

4. Interspecific interactions
Interactions between multiple species
Symbiosis – interaction between two different organisms living in close physical association
Mutualism (benefits both)
Commensalism (benefits one, doesn’t harm the other)
Predation (Parasitism, Herbivory) (benefits one)
Competition
A limiting resource leads to partitioning

5. Competition
Habitat
Resources

6. Principle of Competitive Exclusion
Definition: Two species with similar needs for the same limiting resources cannot co-exist in the same place

7. Resource Partitioning
Definition: The division of environmental resources by coexisting species populations so that the niche of each species differs by one or more significant factors from the niches of all coexisting species populations
For example, hawks and owls both eat small rodents, except hawks hunt by day and owls by night

8. Ecological Niche
Fundamental niche: Refers to the set of resources a population is theoretically capable of using under ideal conditions
Realized niche: the set of resources a population actually uses after resourse partitioning

9. Usable resources
Physiological
constraints
Weather
Competition
Predation
Fundamental
Niche
Realized
Niche

10. Niche Partitioning

11. Niche Partitioning

12. Community Stability Ecological Succession
The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

13. Primary Succession
Starts in areas with exposed rock – volcano/earthquake/etc
Lichens and mosses come first to break down rock by secreting acids, they die and become soil
Very slow succession because soil must be accumulated
Climax community - The stable, mature community that eventually develops from bare rock

15. Secondary Succession
Results from a disturbance – fire/flood/windstorm/landslide
New species come in – usually r-selected species are first
Much more rapid than primary succession
No real “endpoint” because there could be new disturbances