Snake is one example of reptile which classified into the order squamata, whose name means scaly. Snakes have long, thin bodies that are covered with scales. Snakes do not have limbs. There are 3000 species of snakes. Some well known species are rattlesnakes, garter snakes, and water snakes. Generally, snakes paly an important and positive role in nature.
Most snake are non poisonous. Some snakes kill their prey by holding it against the ground and swallowing it alive and whole. The indigo snake and the black racer, for example, are nonpoisonous snakes that obtain food in this way. To take in large prey, the jaws of many snakes are specially hinged to open more widely than usual. Other nonpoisonous snake are constrictors. These wrap themselves around their prey and suffocate it by squeezing with muscular force. The constrictors the swallow the dead prey whole. Rat snakes, the phyton, is a nonpoisonous constrictor. It grows as long as 10 meters, and can consume a small pig.
Poisonous snakes kill their prey by injecting venom, or poison, through a pair of fangs. The fangs, located at the front of the mouth, are large, hollow, curved teeth. The venom moves downs through each fang from a gland either side of the head. These glands make and release venom. There are three families of poisonous snakes. The venomous snakes of two of the families have a pair of tubelike fangs that are always erect. The third family is vipers, which have fangs that are attached to a movable bone. That fangs fold back against the roof of the mouth when not in use.
The first family includes many of the most venomous snakes, such as the cobra, the mamba, and north American coral snake. The coral snake has blunt head and a body with broad rings of red and black that are separated by narrow yellow bands on the scarlet king snake, however, are different from those of the coral snake.
The sea snakes are members of the second family of venomous snakes with nonmovable fangs. These snakes live permanently in the ocean, preying on fish. These very venomous snakes are found in the pacific ocean off the coast of Australia. Many fishermen have been fatally bitten by sea snakes accidentally caught in the fish nets. The old world vipers include the poisonous snakes of Europe, Asia, and Africa, except the cobra. The puff adder belongs to this family, and is the most common poisonous snakes in Africa. It is responsible for more snake bite cases than any other African species.
The pit vipers include the rattlesnake, the copperhead, and the water moccasin of North America. Their name comes from the deep pits on the sides of their heads. These pits are heat-sensing organs that help pit vipers locate warm-blooded prey. The water moccasin eats fish, ducks, and frogs. Copperheads eat mice, other snakes, frogs and toads. The rattlesnake feeds on mice, rats, rabbits and the young of ground-nesting birds.
When a pit viper strikes, its fangs spring forward as the jaws open. The muscles of the poison gland force the venom through canals in the fangs and into the prey. The venom of most snakes is made up of two poisons. One is a hemotoxin, or substance that destroys red blood cells and that alters blood clotting. The other is a neurotoxin, which interferes with the normal function of the nervous system. The neurotoxin causes difficulty in breathing and swallowing it can also interfere with the function of the heart. The sea snakes have a venom that affects muscles.