Introduction
each chapter to indicate sources of the materials presented and to provide
additional information on subjects that can be treated only briefly in the
text. Citations certainly are not intended to be exhaustive, but should lead
serious students into the literature.
The effects ofthe physical environment on behavior and life are such an
intimate part of our everyday experience that one may wonder at the need
to study them. Heat, cold, wind, and humidity have long been common
terms in our language, and we may feel quite comfortable with them.
However, we often misinterpret our interaction with our environment
and misunderstand the environmental variables themselves. Benjamin
Franklin, the early American statesman, inventor, printer, and scientist
alludes to the potential for misunderstanding these interactions. In a letter
to John Lining, written April 14, 1757 he wrote (Seeger, 1973):
My desk on which I now write, and the lock of my desk, are both exposed to
the same temperature of the air, and have therefore the same degree of heat or
cold; yet if I lay my hand successively on the wood and on the metal, the latter
feels much the coldest, not that it is really so, but being a better conductor, it more
readily than the wood takes away and draws into itself the fire that was in my
skin.
Franklin's experiment and the analysis he presents help us understand
that we do not sense temperature; we sense changes in temperature which
are closely related to the flow of heat toward or away from us. The heat
flux, or rate of heat flow depends on a temperature difference, but it also
depends on the resistance or conductance of the intervening medium.
Careful consideration will indicate that essentially every interaction
we have with our surroundings involves energy or mass exchange. Sight
is possible because emitted or reflected photons from our surroundings
enter the eye and cause photochemical reactions at the retina. Hearing
results from the absorption of acoustic energy from our surroundings.
Smell involves the flux of gases and aerosols to the olfactory sensors.
Numerous other sensations could be listed such as sunburn, heat stress,
cold stress, and each involves the flux of something to or from the organism. The steady-state exchange of most forms of matter and energy can
be expressed between organisms and their surroundings as:
Flux = g (C, - C,)
where C, is the concentration at the organism exchange surface, C, is
the ambient concentration, and g is an exchange conductance. As already
noted, our senses respond to fluxes but we interpret them in terms of
ambient concentrations. Even if the concentration at the organism were
constant (generally not the case) our judgment about ambient concentration would always be influenced by the magnitude of the exchange
conductance. Franklin's experiment illustrates this nicely. The higher conductance of the metal made it feel colder, even though the wood and the
metal were at the same temperature.
each chapter to indicate sources of the materials presented and to provide
additional information on subjects that can be treated only briefly in the
text. Citations certainly are not intended to be exhaustive, but should lead
serious students into the literature.
The effects ofthe physical environment on behavior and life are such an
intimate part of our everyday experience that one may wonder at the need
to study them. Heat, cold, wind, and humidity have long been common
terms in our language, and we may feel quite comfortable with them.
However, we often misinterpret our interaction with our environment
and misunderstand the environmental variables themselves. Benjamin
Franklin, the early American statesman, inventor, printer, and scientist
alludes to the potential for misunderstanding these interactions. In a letter
to John Lining, written April 14, 1757 he wrote (Seeger, 1973):
My desk on which I now write, and the lock of my desk, are both exposed to
the same temperature of the air, and have therefore the same degree of heat or
cold; yet if I lay my hand successively on the wood and on the metal, the latter
feels much the coldest, not that it is really so, but being a better conductor, it more
readily than the wood takes away and draws into itself the fire that was in my
skin.
Franklin's experiment and the analysis he presents help us understand
that we do not sense temperature; we sense changes in temperature which
are closely related to the flow of heat toward or away from us. The heat
flux, or rate of heat flow depends on a temperature difference, but it also
depends on the resistance or conductance of the intervening medium.
Careful consideration will indicate that essentially every interaction
we have with our surroundings involves energy or mass exchange. Sight
is possible because emitted or reflected photons from our surroundings
enter the eye and cause photochemical reactions at the retina. Hearing
results from the absorption of acoustic energy from our surroundings.
Smell involves the flux of gases and aerosols to the olfactory sensors.
Numerous other sensations could be listed such as sunburn, heat stress,
cold stress, and each involves the flux of something to or from the organism. The steady-state exchange of most forms of matter and energy can
be expressed between organisms and their surroundings as:
Flux = g (C, - C,)
where C, is the concentration at the organism exchange surface, C, is
the ambient concentration, and g is an exchange conductance. As already
noted, our senses respond to fluxes but we interpret them in terms of
ambient concentrations. Even if the concentration at the organism were
constant (generally not the case) our judgment about ambient concentration would always be influenced by the magnitude of the exchange
conductance. Franklin's experiment illustrates this nicely. The higher conductance of the metal made it feel colder, even though the wood and the
metal were at the same temperature.