Topic 7: How Animals Survive the Cold
The coldest temperature ever recorded on Earth was -128.6 F (-89.2 C) in the winter --on July 21, 1983 -- in Vostok, Antarctica. That's so cold that hot water poured onto the snow will freeze before it even hits the ground. When living creatures are exposed to below-freezing temperatures like this, ice can form in their blood vessels, causing the vessels to stretch or even burst. Frozen ice in the blood stream also steals water from the blood cells, killing them. Without water, and with sharp points on the ice crystals all around, frozen cells can be broken and destroyed. (Have you ever seen a contact lens that's been left out to dry? It often rips in half -- that's what can happen to cells when they lose their water.) But amazingly enough, there are actually some animals that can survive in incredibly cold temperatures.
Different animals have different ways of beating the cold. Emperor penguins spend the winter in Antarctica, surviving temperatures down to -60 C through their bodies' amazing insulation. They have a layer of blubber and then a layer of waterproof feathers that help trap their body heat inside. For even more protection, the penguins huddle together during the winter, each one helping insulate the others against the cold. The hundreds of penguins in the giant huddle shuffle around, taking turns being on the outside of the group -- where the temperature can be up to 20 C lower than in the middle.
Other animals have even more complicated ways of protecting their cells. Some insects -- Antarctica houses little arthropods called springtails, for example -- produce glycerol in their cells. Glycerol acts as an antifreeze that will completely stop ice crystals from forming. In this way, these creatures prevent freezing altogether and can survive down to -40 C.
Instead of preventing freezing, some animals survive cold temperatures by simply letting themselves freeze solid -- while herding any ice crystals in their bodies to spots where they can't do damage. Some varieties of North American turtles and frogs can do this, and near the North Pole, the Arctic woolly bear caterpillar can too. These animals create extra glucose (blood sugar) in their livers and pump the glucose into their cells. Water in these cells has a hard time freezing with all that added glucose and so the only water that freezes is between the cells. A frozen wood frog can survive with a layer of ice right under its skin, but that ice doesn't get into its cells, so the frog will thaw in the summer and return to its normal life.
- Topic 1: Measuring the Cold - Thermometers
- Topic 2: Understanding Heat and Energy
- Topic 3: States of Matter
- Topic 4: Refrigeration
- Topic 5: Cryogenics
- Topic 6: The Quest for Absolute Zero
- Topic 7: How Animals Survive the Cold
- Topic 8: Superconductivity
- Topic 9: Astronomy
- Topic 10: Spaceflight
- Topic 11: Agriculture
- Topic 12: Cold Medicine