72
WHY DON’T
PENGUINS’
FEET FREEZE?
ECOPHYSIOLOGY
T
he central principle of
Darwinian evolution is
that all organisms, from
simple bacteria to complex
mammals, are adapted by natural
selection to survive in a particular
niche and habitat. Ecophysiology—
for which Knut Schmidt-Nielsen’s
book Animal Physiology (1960) was
a vital inspiration—is the study of
an organism’s anatomy and how it
functions (its physiology), as well as
how these characteristics relate to
the challenges posed by its
environment. It shows how the
anatomy of an animal or plant is
linked to its ability to survive, andto its distribution, abundance, and
fertility. Ecophysiology now plays
an important role in helping
scientists understand how the
stresses created by climate change
impact on both wild ecosystems
and cultivated environments.Managing temperature
Ecophysiology has revealed a
number of specific adaptations
for different environments. For
example, animals that live in colder
regions tend to have larger bodies
and smaller legs, ears, and tails
than related species living in
warmer climes. A larger body has
a smaller surface-area-to-mass
ratio, and therefore loses heat more
slowly, while smaller appendages
reduce exposure to frostbite.
In the most extreme cold, the
feet of a warm-blooded animal
are at risk of becoming frozen to
the ground. Mammals in Arctic
regions such as musk oxen and
polar bears are adapted for life in
these conditions by having thick
hairs to insulate their feet.
In the Antarctic, the undersides
of penguins’ feet are insulated
by a thick layer of fat. Penguins
also have a heat-exchange (or
counter-current) mechanism inIN CONTEXT
KEY FIGURE
Knut Schmidt-Nielsen
(1915 –2007)BEFORE
1845 The explorer Alexander
von Humboldt reveals that
plants facing similar ecological
factors also have many
analogous features.1859 Charles Darwin argues
that organisms evolve because
they are adapting to changed
ecological conditions.AFTER
1966 Australian biochemists
Marshall Hatch and Charles
Slack explain that the most
widespread plants are the
ones that photosynthesize
mo s t ef fic ient ly.1984 Peter Wheeler, a British
scientist, suggests that human
bipedalism—the ability to
walk on two legs—evolved as
a thermoregulatory adaptation
that reduces the body’s
exposure to direct sunlight.From a physiological
viewpoint, freshwater
is no more freely
available in the sea
than in the desert.
Knut Schmidt-NielsenUS_072-073_Eco_Physiology.indd 72 12/11/18 6:24 PM