Site Map Question & Answer - Review the Q & A's in the movies

The Raven - why their feet don't freeze even though they are cold

Q: If consuming alcohol increases the volume of blood carried in vessels on the body's surface ("vascular dilation"), would taking a drink increase or decrease core body temperature while you were outside and starting to cool off?

A: Core body temperature would decrease. A greater amount of blood flowing on the surface and in the extremities causes increased heat loss to the environment.

The Lake - water mixing at the change of seasons

Q: If you were a bottom dwelling lake organism needing oxygen, would you prefer a uniform temperature column above or a stratified one?

A: For circulating oxygen throughout the water column, a uniform temperature would be highly preferable. A breeze would circulate all the water, top to bottom.

"The Bunny" - food preference of the snowshoe hare

Q: How could I have improved my food preference experiment?

A: (1) "used a wild snowshoe hare" (2) "left the food with the rabbit longer" (3) "done the test outside over several days" (4) "tried to get juvenile and mature shoots of the same diameter and length" (5) "tried different foods available like aspen, spruce, pine, poplar" (6) "cut older mature shoots"

Vegetation - how deciduous trees adapt to the winter

Q: Why might it be difficult for a plant to replace water lost in the winter?

A: Moisture is locked up in ice crystals and it is unavailable for use by the plant.

Vegetation - regeneration from root mass

Q: The speed at which tissue freezes is often a critical factor in cell damage. In the Yukon what advantage does a root cell have over a stem cell regarding freezing speed?

A: Cells within roots will freeze at a slower rate than those in the stem, making damage less likely.

Heat Loss - calculating the rate of heat loss due to conductance

Q: What affects the rate a body loses heat to the environment due to conductance?

A: Q = k A (Tb- Ta) / d, where
Q is the heat lost due to conduction
k is the thermal conductivity of the body's insulation layer
A is the surface area through which the heat is being lost
Tb is the temperature of the body
Ta is the temperature of the surrounding air
d is the thickness of the body's insulating layer

Heat Loss due to conductance Q = k A (Tb- Ta) / d

Q: A person has fallen through the ice and become soaked. They are rescued so quickly the body temperature is initially unchanged. What in the formula changes to account for their drastic upcoming heat loss?


A: Even if a person's insulating layers are the same thickness as before getting soaked, the thermal conductivity of those layers is drastically increased when wet.

Heat Loss due to conductance Q = k A (Tb- Ta) / d

Q: Which variable in the heat loss formula is affected when a cat tucks all four feet under its body and wraps its tail around?

A: The cat is decreasing its surface area. Decreasing A decreases Q. There is less heat lost due to conductance with this behaviour.

Heat Loss due to conductance Q = k A (Tb- Ta) / d

Q: How can a bear reduce heat loss by hibernating or entering a state of torpor?

A: The temperature of the bear is lowered thus reducing the difference between Tb and Ta, reducing Q, the heat loss.

Heat Loss due to conductance Q = k A (Tb- Ta) / d

Q: Which variable is affected by "chinking" a log cabin?

A: "Chinking" a log cabin increases the temperature inside. It raises the temperature of the air, thus decreasing the difference between Tb and Ta. This lowers the heat loss.

Heat Loss due to conductance Q = k A (Tb- Ta) / d

Q: Which variable in the formula for heat loss due to conductance is affected when a raven fluffs its feathers?

A: When a raven fluffs its feathers it is increasing the thickness of the insulating layer, which is "d" in the formula. As "d" increases, "Q" decreases.

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