Climate and space: microclimates

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Climate and space microclimates

• Macroclimate Large scale weather variation
  (global, regional).
• Microclimate Small scale weather variation,
  usually measured over shorter time period.
• Altitude
• Higher altitude - lower temperature.
• Aspect
• Offers contrasting environments.
• Vegetation
• Can determine ecologically important
  microclimates.
• Ground Color
• Darker colors absorb more visible light.
• Topographic relief and Burrows
• Create shaded, cooler environments.

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Microclimates produce microhabitats
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Aquatic Temperature Differences
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Temperature, biochemistry, and habitat utilization

• Species physiological constraints limit habitat
  breadth
• Enzymes rigid, predictable shapes at low
  temperatures.
• But, reaction rates decrease with low
  temperatures
• High temperatures may distort active sites.
• A range of temperature tolerance can be set by
  enzyme functionality.
• Example acetylcholinesterase
• Rainbow trout (Oncorhynchus mykiss), an ectotherm

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• Substrate acetylcholine
• Neurotransmitter at neuromuscular junctions
• has to be broken down for muscle cell relaxation
• Range of temperature tolerance increased by two
  forms of the enzyme (allozymes).
• Each attains the appropriate conformation in a
  different range of temperatures
• Seasonal shift in gene activation
• 1. One form is produced when water is warm (gt17o
  C)
• 2. An alternative form is produced when water is
  cool (2 - 17o C)

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Temperature and photosynthesis

• Photosynthesis generally affected negatively by
  extreme temperatures.
• Plant species adapted for different temperature
  ranges.

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Temperature extremes and microbial adaptations

• Eg., Psychrophilic marine bacteria of Antarctica.
• Grow fastest at 4o C.
• But can still grow at -5.5o C.
• Eg., Thermophilic archaeans might grow best in
  temperatures of 110o C.
• Range of temperature tolerance typically narrow
• In thermal pools of Yellowstone National Park
• Each thermophile population narrowly adapted to
  the temperature of its own pool.

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Optimal Temperatures
Psychrophilic bacterium
Thermophilic archaean
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Heat Budgets

• Heat movement warmer to cooler areas
• Balancing Heat Budgets
• HS Hm /- Hcd /- Hcv /- Hr - He
• HS Total heat stored in an organism
• Hm Gained via metabolism
• Hcd Gained / lost via conduction
• Hcv Gained / lost via convection
• Hr Gained / lost via electromag. radiation
• He Lost via evaporation

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Heat Exchange Pathways
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• Desert Plant Challenge -- reduce stored heat
• Decrease conductive heating(Hcd)
• Reduce radiative heating (Hr)
• Increase convective cooling (Hcv).

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• Arctic and Alpine Plants Challenge to conserve
  heat
• Two main tactics
• Increase heat gain from solar radiation (Hr).
• Decrease convective cooling (Hcv).

Moss campion
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Body Temperature Regulation

• 1. Poikilotherms
• Without behavioral adjustments, body temperature
  varies directly with environmental temperature.
• 2. Homeotherms
• Body temperature relatively constant and
  independent of environmental temperature.
• A. Ectotherms
• Rely mainly on external heat sources.
• B. Endotherms
• Generate body heat metabolically.

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Thermoregulation by Ectothermic Animals

• Liolaemus multiformis (lizard)
• Unusual distribution exceeds 4800 m (15,738 ft.)
  in Andes Mountains.
• Adaptations involve
• Using burrows
• Dark pigmentation
• Sun basking
• Can get its body temperature to 33oC although air
  temperature may be 1.5o

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• Grasshoppers
• Some species anticipate heat requirements by
  alterations in pigment production during
  development.
• Cooler developmental temperature melanin
  produced and deposited in tissues.
• Warmer developmental temperature less melanin
  and other pigments produced.

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Endothermic metabolic rates and evolutionary
history

• Thermal neutral zone
• Found in homeotherms
• Range of environmental temperatures over which
  the metabolic rate does not change.
• Range /- species specific.

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Thermal Neutral Zones
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Conservation of body heatCountercurrent heat
exchangers
A marine fish
A marine mammal
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Temperature regulation by insects

• Bumblebees maintain temperature of thorax between
  30o and 37o C regardless of air temperature.
• Sphinx moth (Manduca sexta) contraction of
  flight muscles increases thoracic temperature.
• thermoregulates by transferring excess heat from
  the thorax to the abdomen

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Moth Circulation and Thermoregulation
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Temperature Regulation by Thermogenic Plants

• Most plants are poikilothermic ectotherms.
• Exceptions
• e.g., Skunk Cabbage (Symplocarpus foetidus
  family Araceae)(
• Stores energy (starch) in large root
• In late winter, starch is translocated to the
  presumptive inflorescence
• Starch is metabolized generating heat.
• Heat stimulates early flower development.

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Eastern Skunk Cabbage
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Surviving Extreme Temperatures

• Become inactive and reduce metabolic rate
• Seek shelter during extreme periods.
• Hibernation - Winter
• Estivation - Summer
• Torpor e.g., hummingbirds depress metabolism
  when food is scarce and night temps are extreme.