Chapter 5: Temperature Relations
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Outline
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Microclimates
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Temperature and Performance
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Balancing Heat Gain Against Heat Loss
 Body Temperature Regulation
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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.
 Altitude
 Higher altitude - lower temperature.
 Aspect
 Offers contrasting environments.
 Vegetation
 Ecologically important microclimates.
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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 and Animal Performance
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Biomolecular Level

Most enzymes have rigid, predictable
shape at low temperatures

Low temperatures cause low reaction
rates, while excessively high
temperatures destroy the shape.
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Extreme Temperatures and Photosynthesis
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Photosynthesis
6CO2 + 12H2O  C6H12O6 + 6CO2 + 6H20

Extreme temperatures usually reduce rate
of photosynthesis.

Different plants have different optimal
temperatures.
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Optimal Photosynthetic Temperatures
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Temperature and Microbial Activity
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Psychrophilic marine bacteria around
Antarctica grew fastest at 4o C.

Some growth recorded in temperatures as cold
as - 5.5o C.
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Some thermophilic microbes have been
found to grow best in high temperature.
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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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Body Temperature Regulation
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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
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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).
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Temperature Regulation by Plants
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Temperature Regulation by Plants
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Arctic and Alpine Plants

Two main options to stay warm:

Increase radiative heating (Hr).

Decrease Convective Cooling (Hcv).
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Temperature Regulation by Ectothermic Animals
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Eastern Fence Lizard (Sceloporus undulatus)
 Metabolizable energy intake maximized at
33ºC
 Preferred temperature closely matches the
temperature at which metabolizable
energy intake is maximized
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Behavioral thermoregulation
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Temperature Regulation by Endothermic Animals

Heat gain is mainly generated internally
 Metabolism or shivering thermogenesis

Heat loss is reduced by
 Morphological change
 Fat, feather etc
 Countercurrent exchange
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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.

Heat is mainly generated internally
 Metabolism or shivering thermogenesis
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Thermal Neutral Zones
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What is countercurrent heat exchange ?
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Countercurrent Heat Exchange
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Countercurrent Heat Exchange
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Surviving Extreme Temperatures
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Migration
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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The End
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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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Review
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Microclimates
Aquatic Temperatures
The Principle of Allocation
Temperature and Animal Performance
Extreme Temperature and Photosynthesis
Temperature and Microbial Activity
Balancing Heat Gain Against Heat Loss
Body Temperature Regulation
Surviving Extreme Temperatures
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Aquatic Temperatures
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Specific Heat
 Absorbs heat without changing temperature.
3
o
 1 cal energy to heat 1 cm of water 1 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.
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Aquatic Temperatures
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Riparian vegetation influences stream
temperature by providing shade.
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The Principle of Allocation
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Organisms allocate limited energy to a
certain function which then reduces the
amount for other functions.
 This trade-off in energy allocation will
differ among environments with
functions that include growth,
reproduction, and defense against
predators
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The Principle of Allocation
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Levins concluded that the evolutionary
consequences of this trade-off results in
populations having high fitness in one
environment, but lowered fitness in another
environment.
Bennett and Lenski found support for Levins’
Principle of Allocation using experiments
with Escherichia coli grown in different
temperature environments.
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The Principle of Allocation
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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.
 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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