Tuesday 4 February 2014

WHY ARE POLAR BEARS WHITE?


Polar bears have evolved from brown bears.  But they are white, not brown.  So why did they change colour?

The reason for the change is the difference in habitat of the two bears. The polar bear differs from its brown cousin as it lives and hunts on sea ice.  The snow and ice are white so the bears blend in with their surroundings.  Most Arctic animals such as the Arctic fox and hare are white in the winter, but the polar bear is white all year round.  

However, think again.  It is not the fur that is white.  The hairs are actually transparent and it is the light bouncing off them that makes them appear white.  In addition the hair follicle is hollow so there is no melanin present to determine colour.. Even more fascinating is the fact that the skin colour of the polar bear is black.

Polar bears have two layers of hairs that help to insulate them against temperatures as cold as -50F.  Next to the skin is a layer of soft, downy colourless hairs which trap warm air to insulate the skin.  Above these are thick, coarse guard hairs which repel water and are also colourless.

Polar bears have previously turned green in some zoos.  Further investigation by scientists found that algae from pond water inside the enclosure was growing inside the hollow hair fibres and giving the green appearance.

For related articles click onto:
How far is the moon?
How many seas are there in the world?
How big is a giant earthworm?
Is the sea sponge a plant or an animal?
What is a sea sponge?
What is a cuttlefish?
What is a ladybug?
What is a sea anemone?
What is a starfish?
What is acid rain?
What is global warming?
Why is the Dead Sea so salty?
What is the difference between a butterfly and a moth?
What is the difference between an asteroid and a comet?
What is the difference between energy efficient light bulbs and traditional light bulbs?
What is the difference between a fog and a mist?
What is the difference between hard and soft woods?
What is the difference between neon and fluorescent light?
What is the difference between the sea and the ocean?
What is the difference between hibernation and sleep?
What is fracking?
What is global warming?
What is the Gulf Stream?
Why are polar bears white?


No comments:

Post a Comment