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Lecture 7

BIOL 1902 Lecture Notes - Lecture 7: Torpor, Eugenius Warming, Sorbitol


Department
Biology
Course Code
BIOL 1902
Professor
Michael Runtz
Lecture
7

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Lecture 7
(Continuation of what animals do to deal with the extreme cold)
Snow
snow can help animals keep warm.
can be used for the top of beaver lodges.
can be used to insulate animals (like red squirrels) - they burrow into it
to the bottom of the snowpack and move around (at the subnivean
space where it is much warmer).
animals at the subnivean space usually leave a trail behind them
however, they can suffocate if they stay there too long, so they
need to go back up every now and then.
sometimes, snowmobiles that go round and round can press
down the snow so there’ll be no subnivean layer.
key point: under the snow, there is a layer where it is
warmer where animals can move around and find food.
sometimes, animals make a chamber under the snow and stay there.
ex: ruffed grouse snowbed.
generally, it is safe for them to stay there.
however, if it rains over, they are in danger.
Sometimes, animals just bask in the sun to keep warmth.
Some animals do unique things.
ex: black-capped chickadees lower their body core temperature by 12 degrees
celsius.
they enter a deep sleep called torpor.
advantage to lowering their body core temperature:
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it reduces the temperature gradient: the difference in
temperature between the inside and outside.
this allows them to maintain more energy since they don’t
have to try as hard to maintain their core temperature.
they also shiver, shivering is an important means of thermogenesis!
How Ectotherms deal with the extreme cold:
using snakes as an example:
they cannot be out in sub-zero temperatures since they can’t regulate
their body temperature by themselves - they’ll die if they stay in sub-zero
temperatures for long.
they burrow into the ground - into the ground where it stops freezing (at
the frostline: the level in the ground that is associated with freezing,
above the frostline, the ground freezes, below the frostline, it doesn’t
freeze.)
therefore, snakes survive by moving down below the frostline,
and becoming dormant - into their hibernaculum.
this is known as behavioural freeze avoidance.
all adult and most hatchling turtles (along with some frogs) don’t freeze, so they
can escape subzero temperatures by going to the bottom of ponds and lakes.
american toads and most salamanders dig down beneath the frost line.
some ectotherms (in the form of insects) stay above the frost line during the
winter.
some overwinter in the form of eggs.
ex: praying mantises
praying mantises lay eggs which are in a special container
(ootheca) so they won’t die.
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