How do you define a whale? What is the difference between whales and dolphins?

The Order Cetacea contains all of the species of whale and dolphin.

This group is split into two sub-orders.

Most of the whales belong to the 'baleen whale' group.

The other group are the 'toothed whales', and includes the dolphins, porpoises and some whales.

(Click here to read about the 'dolphins and other toothed whales')

from the sieve-like plates that hang down inside the mouth.

The animal opens its huge mouth and water gets sucked in.

The water is then squeezed out with the giant tongue,

and planktonic organisms are caught on these filters.

This suborder includes about 14 species,

including the largest of all animals, the Blue Whale.

But the most commonly seen and famous species is the Humpback (pictured below).

For another wesbsite with more info on whales and the research into them...