BIOE 20C Lecture Notes - Lecture 15: Competitive Exclusion Principle, Herbivore, Commensalism
12 Sep 2016
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Lecture 15 11/19/2015 8:59:00 PM
Community Ecology
• Community: interacting species within a given area
• Population< Community< Biome (spatial scale)
Species Interactions
• Interaction between 2 spp
• Affect fitness of both spp
• Fitness effects: +, -, or 0
• Five basic types of interactions
o Antagonistic interactions (+/- or -/+)
▪ Predation
▪ Herbivory
▪ Parasitism
o Mutualism (+/+)
o Competition (-/-)
o Commensalism (+/0)
o Amensalism (0/-)
Competition
• -/-
• Both spp experience fitness decrease
• Niche:
o Sum total resources used by a species
o Range of conditions it can tolerate
• Species with overlapping niches compete with each other
Competitive Exclusion
• GF Gause
o Hypothesized that 2 spp with same niche cannot co-exist
• =competitive exclusion principle
2 Types of Competition
• Symmetric
o Each species experiences the same relative decrease in
fitness
• Asymmetric
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o One species has greater fitness decrease relative to other
• Asymmetric is more common than symmetric in nature
• Competitive exclusion occurs when competition is asymmetric
Consequence of Asymmetric Competition
• Q: Why aren’t there just a few superior competitors?
• A: Most niches don't completely overlap
o Provides refuge for more inferior competitor
Fundamental vs. Realized Niche
• Fundamental niche: total possible use of the environment by a
species
o Largest potential niche a species can occupy
• Realized niche: actual observed use of the environment by a
species
Two Categories for Competitive Interactions
• Interference competition
o Species interfere with another’s use of a resource
• Exploitation competition
o Species both utilize a resource
o Most efficient consumer wins
Consumption (Antagonistic Interactions)
• One species consumes all or part of another
• 3 types
o Herbivory
o Parasitism
o Predation
Herbivory
• Grazing organisms (herbivores) consume plant tissues
Parasitism
• Parasite consumes relatively small amounts of tissue form a plant
or animal (host)
Predation
• Predator kills and consumes all or most of another organism (prey)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
11/19/2015 8:59:00 pm: community: interacting species within a given area, population< community< biome (spatial scale) Species interactions: interaction between 2 spp, affect fitness of both spp, fitness effects: +, -, or 0, five basic types of interactions, antagonistic interactions (+/- or -/+, predation, herbivory, parasitism, mutualism (+/+, competition (-/-, commensalism (+/0, amensalism (0/-) Competition: both spp experience fitness decrease, niche, sum total resources used by a species, range of conditions it can tolerate, species with overlapping niches compete with each other. Competitive exclusion: gf gause, hypothesized that 2 spp with same niche cannot co-exist, =competitive exclusion principle. Consequence of asymmetric competition: q: why aren"t there just a few superior competitors, a: most niches don"t completely overlap, provides refuge for more inferior competitor. Realized niche: fundamental niche: total possible use of the environment by a species, largest potential niche a species can occupy, realized niche: actual observed use of the environment by a species.
