Chapter 28
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Transcript of Chapter 28
Chapter 28
Community Interactions
Why Are Interactions in Communities Important?
• Community • Interactions limit population size
– Balance between resources and # of individuals
– Exotic species may upset balance
• Interactions influence evolutionary change– Coevolution
Interspecific Competition
• Each species has a unique place in its ecosystem– Ecological niche
• Niches of species never overlap completely– Competitive exclusion
• Competitive exclusion may help determine population distribution– Fundamental niche vs. Realized niche
• Species may evolve to reduce competition– Resource partitioning
What are the Effects of Predator-Prey Interactions
• Coevolution
• Predators consume prey
• Parasites feeding off host but may not kill the host– Herbivores
• Camouflage– Hiding in plain site
Blending in
resemble specific objects
Camouflage assists predators
Camouflage can be beneficial to predators as well
• Bright colors or chemical defenses may warn off predators
Warning coloration
Startle coloration
Warning mimicry
Visual and behavioral mimicry
Chemical Warfare
• Plants have defenses against herbivores – Chemicals
– Tough outer parts
• Symbiosis
– Communalistic • + / neutral
– Mutualistic• + / +
– Parasitic• + / -
Mutualism
Keystone species
How do Communities Change Over Time
• Succession– Pioneers– Climax community
Primary Succession
Secondary Succession