Lecture 15 - Consumer-Resource Interactions, 11/04
• Eating plants or parts of plants
• Parasites - Consume parts of their living prey (host).
• Parasitoids – Consume their host and cause it’s death.
• Response to abundant prey.
Numerical response: how the density of predators changes to the density of prey.
Functional response: number of prey killed per predator as prey density changes.
• A powerful agent of natural selection.
Chemical compounds in plant leaves to deter herbivores.
Coloration to hide (mimicry)
o Toxic model, palatable mimic.
o Requires learning by predator.
o Several species adopt a single coloration or pattern.
Coloration to warn (aposomatic).
• Predator –prey cycle (Theory).
Abundant prey should cause an increase in predators.
Abundant predators should cause prey to decline.
Absence of prey will cause a decline in predators
As long as some prey survive, since predators are rare, prey population should increase again.
• The Lotka-Volterra Predator-Prey Cycle
• Stability of Predator-Prey Systems in Nature.
o Spatial heterogeneity or complexity of environment.
Refuge and recovery.
o Evolved defenses that reduce vulnerability.
o Alternative prey, prey switching
• Keystone Species
o The species whose presence/absence, or increase/decrease in abundance, strongly affects other species in the community.