It happened over 300 years in Holland

constant and warm body temperature. Fish, on the other hand, are more like
reptiles. Most are cold-blooded. This means they change their body temperature
to match the surrounding water.
(3) Whales and fish are similar in some ways. Both have fins and a tail which
helps them swim and stay upright in the water. But these similarities are in
appearance only. Whales move their body through the water with the help of their
horizontal tail which flaps up and down to propel
them through the water. Fish, on the other-hand,
move their tails from side to side. Even though they
are huge creatures, whales can reach astounding
speeds when swimming. Killer whales can swim up to
60 kph, some dolphins 30 kph, while the large Fin Whale
cruises along at 22 to 26 kph. Right Whales and Grey Whales
are somewhat slower, with a top speed of about 11
kph. How fast fish swim depends on their
size and shape. Herring a small fish, swims
at only 6 kph. Swordfish are the speedsters. They have been clocked
at 96 kph. Both creatures will swim at speeds if they are chasing or
escaping an enemy. It requires too much energy to do it any other time.

(4) Whales are divided into two groups; baleen

whales and toothed whales. The baleen or whalebone
whales have no teeth. Instead, a flexible fingernaillike
substance called baleen is suspended from the
upper jaw. It is used to strain food from the large
gulps of water the whales takes in its mouth and then
spits out. The baleen group of whales include 10
species. Most of the largest whales are in the baleen
group. The other group is the toothed whales. As
their name suggests, they have teeth. This group has
66 species and includes sperm whales, killer whales,
dolphins and porpoises.
(5) Fish are placed in three groups; those that have
no jaws like lampreys, those that have cartilage for
bones like rays and sharks and those that have bony