Low Temperatures

Question 1

Benefits of burrowing

Answer 1

The temperature is relatively high and it is a windless microclimate
Runways and tunnels connect food caches with nests where animals curl up, alone or together, to conserve heat
Energy costs are 15-50% lower than above ground, and they are also less vulnerable to predators

Question 2

How safe are brown lemmings

Answer 2

It is thought possible that the fox may be able to detect magnetic fields in the retina of its eye.
Research suggests that the fox sees a shadow on its retina that is darkest toward magnetic north
When the shadow lines up with where the fox perceives the sound of a mouse, for example, it launches itself in the air, coming straight down on its prey

Question 3

Insulation

Answer 3

o External insulators are much more effective than internal ones

o 2cm of mammalian fur has about the same insulating properties as a layer of 60-70cm of blubber

o The thicker the trapped layer of air, the more effective the fur is as an insulator

o Polar bear guard hairs are hollow, and the hollow space has a rough interior. The trapped air inside the hair provides additional insulation

Question 4

Fur

Answer 4

• Fur in arctic mammals also varies with season

o Winter coats are thicker and better insulating than summer coats

• Coat colouration can also change between summer and winter in some species. This appears to be mainly down to camouflage.
• When fur gets wet it looses much of its insulating properties.

o Therefore most marine mammals rely on a thick layer of fat or blubber to keep warm

o Blubber (white fat cells) is also relatively metabolically inactive compared with other body tissues and thus requires little blood supply

Question 5

Controlling heat loss from the skin

Answer 5

Manage the rate of blood flow near the skin surface
Peripheral vessels constrict/shunt vessels dilated = no heat loss
Peripheral vessels dilated/shunt vessels constricted = heat loss

Question 6

Feathers

Answer 6

trap a layer of air
feathers made waterproof by oil from the preen gland
Most birds grow feathers in narrow tracts, and then fluff them out to cover all the exposed skin

Question 7

Penguin Feathers

Answer 7

Penguins lose heat from head/ flippers where feather coverage is poor
Penguins have evolved modified plumage that has highly effective insulating properties
Penguins, have many more feathers, and almost the entire body surface is covered with a dense, tightly packed growth of feathers
The scale – like outer parts overlap, and are almost impermeable to wind or water.
On the lower shafts grow tufts that form an insulating layer of fluffy down
Besides feathers, penguins also have a thick layer of blubber just below the skin