Temperature Relations
Chapter 4
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Microclimates
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Macroclimate: Large scale weather variation.
Microclimate: Small scale weather variation,
usually measured over shorter time period.
 Altitude
 Higher altitude - lower temperature.
 Aspect
 North-face shaded in Northern Hemisphere.
 Offers contrasting environments.
 Vegetation
 Ecologically important microclimates.
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North
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Microclimates
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Ground Color
 Darker colors absorb more visible light.
Boulders / Burrows
 Create shaded, cooler environments.
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Temperature Response of
Metabolic Processes
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Enzymes:
 Optimum temperature.
 Multiples isozymes with different optima.
Complex Processes:
 Photosynthetic optimal temperature.
 Acclimation within species (physiological)
Whole organism:
 Cardinal temperatures (min, optimum, max)
 Bacteria to man.
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04_08.jpg
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Optimal Photosynthetic Temperatures
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Body Temperature Regulation
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Poikilotherms
 Body temperature varies directly with
environmental temperature.
Ectotherms
 Rely mainly on external energy sources.
 Behavior and anatomical features used.
Endotherms
 Rely heavily on metabolic energy.
 Homeotherms maintain a relatively constant
internal environment (birds and mammals)
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Balancing Heat Gain Against Heat Loss
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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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Temperature Regulation by Plants
(ectothermy)
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Temperature Regulation by Animals
(ectothermy)
• Move to …. (e.g. Angilletta’s lizards)
• Pigmentation (e.g. Curruther’s grasshoppers)
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Temperature Regulation by Endothermic Animals
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Cooling:
 Anatomical features.
 Evaporative cooling.
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Thermal neutral zone is the range of environmental
temperatures over which the metabolic rate of a
homeothermic animal does not change.
 Breadth of TNZ varies among endotherms.
 Tropics narrow TNZ
 Polar broad TNZ
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Thermal Neutral Zones
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Endotherms Surviving Extreme Temperatures
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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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Countercurrent Heat Exchange
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http://www.bio.davidson.edu/Courses/anphys/2000/CrawfordR/ccbloodflow.htm
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Temperature Regulation by Endothermic Animals
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Warming Insect Flight Muscles
 Bumblebees maintain temperature of
thorax between 30o and 37o C regardless
of air temperature and flight activity.
 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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Temperature Regulation by Thermogenic Plants
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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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Sources for images
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http://astrosun.tn.cornell.edu/~shami/smoky/lizard.jpg
http://www.sf.airnet.ne.jp/~yasuda/main/greenland/mo02.jpg
http://www.gotostcroix.com/hiking/images/cactus.jpg
http://wenlin.network.com.tw/goat/Old_Data/~english/alpine_plant/450/plant_29.
JPG
http://www.americansouthwest.net/slot_canyons/photographs700/creosotebush.
jpg
http://en.wikipedia.org/wiki/Image:Bumblebee_closeup_cropped.jpg
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