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Community Ecology
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Iowa State University
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Define a Community:
An assemblage of all species in an area that live close enough to one another to interact
The interactions of organism within a community is dependent on the number of species
present and the abundance of each species.
How do species interact with each other? Are these interactions positive or negative?
- Competition (-/-)
two or more species going after the same resource (must be limited), specie don’t have to see
each other -- corn and foxtail compete for light
- Predation, Herbivory, Parasitism & Disease (+/-)
harm or death to one animal, nutrients to other
- Mutualism (+/+)
both species benefit, acacia and ants, igrets and cattle
-Commensalism (+/0)
one or more species benefit without negatively impacting another species
Whats the difference between intraspecific and interspecific?
intra - within species, inter between species
What is a Niche? A Fundamental Niche? A Realized Niche? How can you identify Niches?
an organism’s ecological role in the environment - where it lives, what it eats, when it eats
Fund - where an organism could live if there was no competition, Realize, where an organism
actually lives
Test, take on species away and see what the other one does, repeat with other
How do niches relate to the Competitive Exclusion Principal?
exact same resource, exact same time, exact same place, one of them will go extinct - two
organisms cannot occupy the same niche
List the 4 ways that help speciation and prevent competition between all species:
1. Resource partition (eat drink migrate at different times, to different places)
2. Keystone Predators
3. Disturbance (2,3 knock back the most competitive species and prevent competition)
4. Spatial Variation (heterogeneity)
Symbiosis is the co-evolution between two species with a relationship that is restricted
(interspecific), give 3 examples of forms of symbiosis that we have talked about:
- Parasitism (+/-)
- Mutualism (+/+)
-Commensalism (+/0)
Within Predation there are 3 ways prey can help themselves, what are they:
1. Passive Defenses in Prey (camo)
2. Active Defense in Prey (skunk, porcupine, poison frog)
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3. Mimicry in Prey
- Batesian Mimicry - harmless species mimics a harmful one
-Mullerian Mimicry - two harmful species mimic each others appearances,
advantageous to most
Evidence indicates that Competition and predations are the key process driving community
dynamics. Other factors, such as dominant species and keystone species relate to the trophic
structure of a community.
Draw a food chain (doesn't have to include specific organism) including the 4 main stages of
the food chain:
Decomposers <- consumers <- all other levels of consumers <- primary consumers <- primary
producers
Whats the differences between a dominant species and keystone species?
Dominant, what you’ll see most of, has effect over other species
not always most abundant, but influences whole community - change without them