FREE ESSAY ON DOLPHINS

DOLPHINS

DOLPHINS AND PORPOISES
Dolphins and porpoises are mammals. They breathe air and give birth to living young then
they suckle. They belong to the order or group of mammals called cetaceans, which include
whales. Dolphins have beaklike mouths. Porpoises have bunt mouths and are smaller than
dolphins. But both dolphins and porpoises are toothed whales, and their close relatives
include the killer, sperm and pilot whale.
Cetaceans are mammals that returned to the sea. Hind legs disappeared and were replaced
by a strongly muscled tail end and flat tail or fluke. The front legs have evolved into
flippers. One primitive specie- the Bouto or the river dolphin of the Amazon and other
southern American rivers- has finger bones that show clearly in their flippers. Most
mammalian hair has also disappeared from the streamlined body of the cetacean.
The nostrils for breathing air have gradually moved to the forehead and, in the dolphins
and porpoises have become one blow whole, which leads right to the lungs instead of the
mouth and throat. The river living dolphins such as the Bouto must come up for air every
30 seconds, but the ocean dolphins can stay in the water for a few minutes. When they
surface, a great spout of moist, used air is comes out from the blow wholes. More air is
taken in, and they dive again.
A dolphin or porpoise baby is born in the water. The mother and another female dolphins,
which acts as a "nurse", then rush into the surface for the baby's first breath of air.
They introduce the baby to the deeper water and longer stays under the water the first
few weeks. At first they return to the surface for the baby to suckle it's mothers milk.
Usually only one baby is born at a time. It spends a full year feeding on milk and strays
from its mother