Life in Varying Environments

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Life in Varying Environments

1. Sources of environmental variation
2. Behavioral responses
3. Acclimation
4. Developmental responses
5. Avoidance strategies

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• Any environment has a set of distinct
  microhabitats or microenvironments, each with its
  own microclimate

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• Microhabitat part of the environment that
  individual organism directly encounters at one
  time
• Microhabitats vary in space...
• vegetation cool
• aspect north faces are shadier
• ground color darker is hotter
• rocks, burrows cool spots with less variation

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• and time

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Each organism has an optimum environment
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so microhabitat selection is important.
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• Acclimation is a reversible shift in the range of
  physiological tolerances of the individual.
• Some examples
• growing thicker fur in winter
• producing smaller leaves in the dry season
• increasing the number of red blood cells at
  higher elevations
• producing enzymes with different temperature
  optima

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• Acclimation is a reversible response.
• Developmental plasticity is a permanent response
  triggered by environmental conditions early in
  life.
• found in habitats with persistent variation

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• When the environment becomes too extreme,
  organisms
• cannot adapt to such extreme conditions
• or they can adapt, but such adaptations would be
  too costly
• Alternative strategies
• migration
• storage
• dormancy

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• Migration moving to another region with more
  suitable conditions
• triggered by
• food supplies
• occasionally water
• found in every kind of animal, especially
• birds
• locusts
• can be obligate (always occurs) or facultative
  (only happens under certain circumstances)

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• Storage accumulating resources during favorable
  times for use in unfavorable times
• Plants accumulate water, nutrients during good
  times
• cacti store water during rainy periods
• plants in fire-prone areas store nutrients in
  their roots to allow resprouting after fire
• Animals
• accumulate fat reserves during warm, wet periods
• store food in burrows, dens, middens

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American Pika
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Fire-prone plants store nutrients in their roots
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• Dormancy becoming inactive
• Plants
• shed leaves during drought, cold
• overwinter as seeds
• Animals
• hibernation a dormant, low-metabolism state
  during winter
• estivation a dormant, low-metabolism state
  during summer
• diapause a low-metabolism resting state found
  in insect larvae or eggs

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• How do organisms sense impending environmental
  severity?
• Proximate factors are cues used to assess
  environmental factors
• day length
• temperature
• rainfall
• proximate factors are predictors of ultimate
  factors
• Ultimate factors are features of the environment
  which directly affect well-being
• food supply
• water availability