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Consumer-resource Interactions (Chapter 17). Overview of community interactions Predator-prey relationships Host-parasite relationships Herbivore-plant relationships. Types of consumer-resource interactions.

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consumer resource interactions chapter 17
Consumer-resource Interactions (Chapter 17)
  • Overview of community interactions
  • Predator-prey relationships
  • Host-parasite relationships
  • Herbivore-plant relationships
slide4
Characteristics of predators
  • Size of prey is proportional to size of predator
    • large prey can be dangerous
    • small prey don’t provide enough energy
slide5
Cooperative hunting
    • allows larger prey to be taken
  • Ability to tear skin and flesh
    • sharp teeth
    • hooked beaks and claws
    • jaws that open very widely
slide6
Tactics to Avoid Being Eaten
  • Escape
    • early detection of predators
    • speed
  • Hiding
    • stay near cover
    • reducing activity
  • Physical defenses
    • armor
    • horns, antlers, claws, teeth, etc.
    • large body size
slide9
Chemical defenses
    • noxious sprays
    • poisonous chemicals in body tissues
    • often accompanied by aposematic (bright, contrasting) warning coloration
slide10
Mimicry
  • Batesian mimicry – a palatable or harmless organism appears similar to an unpalatable or harmful organism
  • Associated with aposematic colors
slide12
Müllerian mimicry – when unpalatable species evolve to resemble one another
  • creates more opportunities for predators to learn to avoid them
slide13
Large groups
    • increased detection of predators
    • decreased odds that any individual is eaten
  • Predator satiation
    • overwhelming predator populations by producing many, many seeds or young at irregular intervals
    • masting – synchronous, widespread seed production
slide16
Parasite-host Relationships
  • Parasite – consumes part of a living prey organism (host)
    • can be internal or external
    • do not directly kill the host
  • Parasitoid – animals that lay eggs on living organisms and whose larvae eat and kill the host
    • usually flies and wasps
slide19
Virulence – the ability of a parasite to do harm to its host
  • For parasites, there is a tradeoff
    • too little virulence: parasite is unable to survive, reproduce
    • too much virulence: parasite kills its host and cannot reproduce
  • Most parasites have low virulence
slide20
Herbivores – eat whole plants or parts of plants.
  • Grazing – eating grasses, herbaceous vegetation, or algae
  • Browsing – eating woody vegetation
slide21
Herbivore impacts on plant communities:
  • Herbivores can dramatically reduce plant populations
    • grasslands: herbivores consume 30-60% of above-ground vegetation
    • forests: herbivores consume 10% of veg.
  • Some plants are adapted to be grazed
slide23
Adaptations of herbivores:
  • Teeth with large grinding surfaces or cutting surfaces
  • Long guts
  • Stomach with fermentation chambers
slide24
Plant defense against herbivory
  • Low nutritional value of plant tissues
  • Toxic compounds
  • Structural defenses
    • spines
    • hairs
    • hard shells on seeds
    • sticky gums and resins
slide26
Chemical Defenses of Plants
  • Secondary compounds – chemicals made by plants to defend themselves against herbivores
    • tannins – bitter-tasting chemicals that inhibit digestion of proteins
  • Can have a variety of toxic effects on herbivores
  • Herbivores often evolve resistance to secondary compound
slide27
Chemical defenses can be
  • constitutive – maintained at all times, or
  • induced – manufactured in response to herbivore damage
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