Temperature Relations

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Temperature Relations

• Chapter 4

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Outline

• Microclimates
• Aquatic Temperatures
• Temperature and Animal Performance
• Extreme Temperature and Photosynthesis
• Temperature and Microbial Activity
• Balancing Heat Gain Against Heat Loss
• Body Temperature Regulation
• Plants
• Ectothermic Animals
• Endothermic Animals
• Surviving Extreme Temperatures

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Microclimates

• Macroclimate Large scale weather variation.
• Microclimate Small scale weather variation,
  usually measured over shorter time period.
• Altitude
• Higher altitude - lower temperature.
• Aspect
• Offers contrasting environments.
• Vegetation
• Ecologically important microclimates.

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Microclimates

• Ground Color
• Darker colors absorb more visible light.
• Boulders / Burrows
• Create shaded, cooler environments.

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Aquatic Temperatures

• Specific Heat
• Absorbs heat without changing temperature.
• 1 cal energy to heat 1 cm3 of water 1o C.
• Air - .0003 cal
• Latent Heat of Evaporation
• 1 cal can cool 580 g of water.
• Latent Heat of Fusion
• 1 g of water gives off 80 cal as it freezes.
• Riparian Areas

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Aquatic Temperatures

• Riparian vegetation influences stream temperature
  by providing shade.

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Temperature and Animal Performance

• Biomolecular Level
• Most enzymes have rigid, predictable shape at low
  temperatures
• Low temperatures cause low reaction rates, while
  excessively high temperatures destroy the shape.
• Baldwin and Hochachka studied the influence of
  temperature on performance of acetylcholinesterase
  in rainbow trout (Oncorhynchus mykiss).

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Extreme Temperatures and Photosynthesis

• Photosynthesis
• 6CO2 12H2O ? C6H12O6 6CO2 6H20
• Extreme temperatures usually reduce rate of
  photosynthesis.
• Different plants have different optimal
  temperatures.
• Acclimation Physiological changes in response to
  temperature.

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Optimal Photosynthetic Temperatures
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Temperature and Microbial Activity

• Morita studied the effect of temperature on
  population growth among psychrophilic marine
  bacteria around Antarctica.
• Grew fastest at 4o C.
• Some growth recorded in temperatures as cold as -
  5.5o C.
• Some thermophilic microbes have been found to
  grow best in temperatures as hot as 110o C.

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Optimal Growth Temperatures
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Balancing Heat Gain Against Heat Loss

• 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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Body Temperature Regulation

• Poikilotherms
• Body temperature varies directly with
  environmental temperature.
• Ectotherms
• Rely mainly on external energy sources.
• Endotherms
• Rely heavily on metabolic energy.
• Homeotherms maintain a relatively constant
  internal environment.

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Temperature Regulation by Plants

• Desert Plants Must reduce heat storage.
• Hs Hcd ? Hcv ? Hr
• To avoid heating, plants have (3) options
• Decrease heating via conduction (Hcd).
• Increase conductive cooling (Hcv).
• Reduce radiative heating (Hr).

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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Temperature Regulation by Plants
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Temperature Regulation by Plants

• Arctic and Alpine Plants
• Two main options to stay warm
• Increase radiative heating (Hr).
• Decrease Convective Cooling (Hcv).
• Tropic Alpine Plants
• Rosette plants generally retain dead leaves,
  which insulate and protect the stem from
  freezing.
• Thick pubescence increases leaf temperature.

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Temperature Regulation by Ectothermic Animals

• Eastern Fence Lizard (Sceloporus undulatus)
• Metabolizable energy intake maximized at 33ºC
• Preferred temperature closely matches the
  temperature at which metabolizable energy intake
  is maximized
• Grasshoppers
• Some species can adjust for radiative heating by
  varying intensity of pigmentation during
  development.

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Temperature Regulation by Endothermic Animals

• Thermal neutral zone is the range of
  environmental temperatures over which the
  metabolic rate of a homeothermic animal does not
  change.
• Breadth varies among endothermic species.

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Thermal Neutral Zones
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Temperature Regulation by Endothermic Animals

• Swimming Muscles of Large Marine Fish
• Lateral swimming muscles of many fish (Mackerel,
  Sharks, Tuna) are well supplied with blood
  vessels that function as countercurrent
  heat-exchangers.
• Keep body temperature above that of surrounding
  water.

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Countercurrent Heat Exchange
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Temperature Regulation by Endothermic Animals

• Warming Insect Flight Muscles
• Bumblebees maintain temperature of thorax between
  30o and 37o C regardless of air temperature.
• Sphinx moths (Manduca sexta) increase thoracic
  temperature due to flight activity.
• Thermoregulates by transferring heat from the
  thorax to the abdomen

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Moth Circulation and Thermoregulation
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Temperature Regulation by Thermogenic Plants

• Almost all plants are poikilothermic ectotherms.
• Plants in family Araceae use metabolic energy to
  heat flowers.
• Skunk Cabbage (Symplocarpus foetidus) stores
  large quantities of starch in large root, and
  then translocate it to the inflorescence where it
  is metabolized thus generating heat.

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Eastern Skunk Cabbage
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Surviving Extreme Temperatures

• Inactivity
• Seek shelter during extreme periods.
• Reducing Metabolic Rate
• Hummingbirds enter a state of torpor when food is
  scarce and night temps are extreme.
• Hibernation - Winter
• Estivation - Summer

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Review

• Microclimates
• Aquatic Temperatures
• Temperature and Animal Performance
• Extreme Temperature and Photosynthesis
• Temperature and Microbial Activity
• Balancing Heat Gain Against Heat Loss
• Body Temperature Regulation
• Plants
• Ectothermic Animals
• Endothermic Animals
• Surviving Extreme Temperatures

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