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Summary of Lecture 1 Chapter 50. Definitions of ecology and levels of organization Abiotic factors that determine distribution patterns of organisms (solar radiation, latitudinal variation in temperature and rainfall, effects of water and topography)

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Summary of Lecture 1Chapter 50

  • Definitions of ecology and levels of organization

  • Abiotic factors that determine distribution patterns of organisms (solar radiation, latitudinal variation in temperature and rainfall, effects of water and topography)

  • Aquatic and terrestrial biomes: understand the key features of those biomes that are reviewed

  • Basic organismal ecology: the principle of allocation of resources (costs of regulating or conforming)


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Organismal Ecology

  • Investigations of physiological, morphological or behavioral responses: answering proximate questions. “By what mechanism does this response occur”?

  • Investigations that seek to explain how responses arose in evolutionary terms: answering ultimate questions. “Does the response maximize fitness (survival and reproductive success)?


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Responses to environment in ecological time

  • Physiological e.g. tolerance curves identify optimum conditions and capacity to operate beyond these (Goldfish example L1)

  • Morphological e.g. acclimation (reversible changes e.g. winter fur) & irreversible changes (e.g. leaf structural variation correlated with environmental gradients)

  • Behavioral e.g. rapid reactions, migratory behavior, social behavior (this lecture)


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Behavioral Ecology

  • See Chapter 51, pp 1053-1060

  • Find notes at www.ent.orst.edu/jepsonp

    • Lecture 2!


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Behavioral Ecology

  • A blend of both proximate and ultimate questions

  • Proximate: e.g. environmental triggers; underlying genetics and physiology

  • Ultimate: e.g. effect on fitness

  • Integration of behavior and evolutionary ecology led to the field of behavioral ecology 25 years ago


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Behavior resulting from genes and environment

  • Both genes and environment influence behavior

  • Behaviors exhibit phenotypic variation, like other traits

  • e.g. nest building in lovebirds: strong genetic influence, but capacity to modify with experience (following slide)

  • Most behaviors have very broad norms of reaction


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Fischers lovebird cuts long strips of vegetation for nest building

Peach-faced lovebirds cut short strips and tuck them into tail feathers

Experimental hybrids exhibit intermediate behavior. Strips are mid length, and birds fail to let go when tucking strips into tail. Birds learn to use beaks for transport

After years, birds still turn back, revealing a genetic component to behavior: but behavior is modified by experience


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Do innate behaviors exist? building

  • E.g. newly hatched birds begging for food

  • Behavior does not appear to alter across a range of environmental conditions

  • Ultimate cause for apparent innate behavior may be that automatic behavior maximizes fitness to such a degree that variants have been lost


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Classical Ethology building

  • Von Frisch, Lorenz, Tindbergen

  • Investigation of Fixed Action Patterns (FAP’s), elicited by sign stimuli

  • e.g. red bellies, even on unrealistic models, elicit aggressive responses by male sticklebacks (next slide)

  • Stereotypic behaviors occur throughout the animal kingdom


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Classical demonstration of innate behavior building

Red bellies on fish models elicit aggressive territorial responses in male sticklebacks

Male fish will not attack invading males that lack the red belly


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Classical ethology buildingTindbergen

Careful experimentation demonstrated that Digger wasp females locate nest using visual cues (arrangement of landmarks, not the objects themselves)


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Behavioral ecology building

  • Exploits evolutionary hypotheses: do animals behave in a way that maximizes fitness?

  • Research based upon the expectation that animals will increase Darwinian fitness by optimizing behavior


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Songbird repertoires building

  • Individual male birds exhibit repertoires of song

  • Does this confer a benefit in terms of fitness?

  • Hypothesis: Do females prefer to mate with males that have a large song repertoir?


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Sonograms of the partial repertoire of one male brown-headed cowbird

Some species can generate hundreds of song variants

Does this confer a fitness advantage?



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Optimal foraging behavior cowbird

  • Food is not taken randomly

  • Search images may guide to prey, with switching when prey become rare

  • Does behavior maximize the profitability of foraging?

  • Profitability = energetic return per unit of effort

  • Easy to develop testable hypotheses


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Optimal foraging cowbird

  • E.g. Bluegill sunfish feeding on Daphnia

  • Optimal foraging theory predicts that fish will be more selective when prey become abundant enough to justify this energetically


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“Apparent size” used to select prey cowbird

Small prey

Low prey density

High prey density

Medium prey

% available

Large prey

Predicted diet

Large prey favored at high density, but not to extent predicted

Observed diet


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