Temperature Relations
Chapter 4
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Outline
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Microclimates
Aquatic Temperatures
Temperature and Animal Performance
Extreme Temperature and Photosynthesis
Temperature and Microbial Activity
Balancing Heat Gain Against Heat Loss
Body Temperature Regulation
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Plants
Ectothermic Animals
Endothermic Animals
Surviving Extreme Temperatures
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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.
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Altitude
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Aspect
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Higher altitude - lower temperature.
Offers contrasting environments.
Vegetation
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Ecologically important microclimates.
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Microclimates
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Ground Color
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Darker colors absorb more visible light.
Boulders / Burrows
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Create shaded, cooler environments.
4 4
Aquatic Temperatures
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Specific Heat
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Absorbs heat without changing temperature.
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1 cal energy to heat 1 cm3 of water 1o C.
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Latent Heat of Evaporation
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1 cal can cool 580 g of water.
Latent Heat of Fusion
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Air - .0003 cal
1 g of water gives off 80 cal as it freezes.
Riparian Areas
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Aquatic Temperatures
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Riparian vegetation influences stream
temperature by providing shade.
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Temperature and Animal Performance
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Biomolecular Level
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Most enzymes have rigid, predictable shape at
low temperatures
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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
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Photosynthesis
6CO2 + 12H2O  C6H12O6 + 6CO2 + 6H20
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Extreme temperatures usually reduce rate of
photosynthesis.
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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
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Morita studied the effect of
temperature on population
growth among psychrophilic
marine bacteria around
Antarctica.
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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
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HS = Hm  Hcd  Hcv  Hr - He
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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
13 13
Body Temperature Regulation
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Poikilotherms
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Ectotherms
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Body temperature varies directly with
environmental temperature.
Rely mainly on external energy sources.
Endotherms
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Rely heavily on metabolic energy.
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Homeotherms maintain a relatively constant internal
environment.
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Temperature Regulation by Plants
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Desert Plants: Must reduce heat storage.
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Hs = Hcd  Hcv  Hr
To avoid heating, plants have (3) options:
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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
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Arctic and Alpine Plants
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Two main options to stay warm:
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Increase radiative heating (Hr).
Decrease Convective Cooling (Hcv).
Tropic Alpine Plants
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Rosette plants generally retain dead leaves, which
insulate and protect the stem from freezing.
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Thick pubescence increases leaf temperature.
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Temperature Regulation by Ectothermic
Animals
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Eastern Fence Lizard (Sceloporus undulatus)
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Metabolizable energy intake maximized at 33ºC
Preferred temperature closely matches the
temperature at which metabolizable energy intake
is maximized
Grasshoppers
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Some species can adjust for radiative heating by
varying intensity of pigmentation during
development.
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Temperature Regulation by Endothermic
Animals
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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 varies among endothermic species.
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Thermal Neutral Zones
20 20
Temperature Regulation by Endothermic
Animals
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Swimming Muscles of Large Marine Fish
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Lateral swimming muscles of many fish
(Mackerel, Sharks, Tuna) are well supplied with
blood vessels that function as countercurrent
heat-exchangers.
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Keep body temperature above that of surrounding water.
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Countercurrent Heat Exchange
22 22
Temperature Regulation by Endothermic
Animals
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Warming Insect Flight Muscles
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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.
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Thermoregulates by transferring heat from the thorax to
the abdomen
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Moth Circulation and Thermoregulation
24 24
Temperature Regulation by Thermogenic
Plants
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Almost all plants are poikilothermic
ectotherms.
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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
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Inactivity
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Seek shelter during extreme periods.
Reducing Metabolic Rate
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Hummingbirds enter a state of torpor when food is
scarce and night temps are extreme.
Hibernation - Winter
Estivation - Summer
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Review
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


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
28 28
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