Subject: RE: Whale

Rui (rprieto@dop.uac.pt)
Mon, 24 Aug 1998 13:13:37 -0000

I'm a student in Singapore, and I would like to ask you a question.

If Whale is a mammal, why can't it lives on land like other animals, since
it needs to surface to breathe?

Thank you.

Sincerely,
Ellyse

Hello Ellyse,

This is my first mail from Singapure. How exciting.
Your question is very interesting.

Cetaceans descend from terrestrial animals. Some 60 million years ago, some
animals probably related with camels and hypos, started colonising the
shores of a sea called the Tethys sea (which does not exist nowadays), maybe
because it was easyer to find food there or because there were less
predators in the water, who knows? With time the species started to suffer
more and more adaptations to the aquatic environment, loosing fur, becoming
more streamlined, having the nares moved to the top of the head (this way
they dont have to raise the head to beath), loosing the hind limbs (its
easier to swim if the drag caused by the water is small. Therefore the more
"torpedo" shaped the body is the better).
Eventually the changes undertaken were so big (it took millions of
years)that cetaceans were more similar to fishes in shape than to other
mammals. That's why many people tought they were fishes for a long time.
Today a cetacean cannot walk on land because of the shape of the body, and
when they are out of the water they can breath, but the body is not prepared
to support it's weight without the help of the water (when you swim, don't
you feel lighter?) and the the lungs are slowly crushed, if the animals are
on their bellies. The skin is also sensitive and have to be moist all the
time or it starts to peel very badlycausing serious sunburns.

Thats why cetaceans can no longer live in dry land,

To find more about this, try these links:
http://earth.ics.uci.edu/faqs/faq-transitional/part2b.html#ceta
http://www.nature.ca/notebooks/english/mon2.htm
http://whales.magna.com.au/DISCOVER/

Cheers,

Rui  :-+);