SNAKES Essays - Colubrids, Venomous Snakes, , Term Papers

SNAKES Justin Keith Mr. Curtwright Biology Keith 1 Have you ever wondered exactly what a snake is? Snakes are elongated, limbless reptiles that have often appeared in art and mythology. Scientists have currently discovered an estimated 2,500-3,000 living species of snakes living throughout the world except in the arctic regions. There is one exception to the old world viper, which has been found as far north as Scandinavia (60? North Latitude). The size variation of snakes ranges from slender blind snakes (family Leptotyphlopidae) which reaches a maximum length of 13cm (5 in.), to the largest snake on record, the Asiatic reticulated python, which attained a record length of 10m (33 ft). Have you ever asked anyone what the phyical characteristics of a snake is? To answer your question: Snakes lack limbs, a sternum (breast bone), shoulder girdle, exterior ear openings, and urinary bladder, and most snakes (but not all) lack a pelvic girdle. There are two types of snakes: constrictors and poisonous. Constrictors will either stalk their prey or lay very still until Its prey come near it. It will then strike forward and wrap around the prey crushing it and cutting off all air supply. The initial strike takes less than one-half second. It will then swallow the prey animal head first because the hair of animals folds backwards and makes it easier to swallow. Poisonous snakes inject a very potent venom into their prey Keith 2 through fangs. There are three different class of venomous snakes: Opisthoglyphus (rear fanged), Proteroglyph (front fanged, with holes pointing outward for "spraying") and Solenoglyph (front fanged and carved). The most common of these three are Solenoglyphs, which have fangs that can be folded along the roof of the mouth. All snakes have powerful digestive enzymes to breakdown the hair, bones, and other parts of their preys' body. As part of the digestive system the salivary glands also produce powerful enzymes. If saliva containing these enzymes enters the wounds of a prey animal, it not only starts the digestive process, but also may cause such serous tissue damage that the prey dies. The destructive substances in a snakes venom include neurotoxins and hemotoxins. Neurotoxins paralyze the central nervous system and cause heart and respiratory failure; hemotoxins destroy blood vessels and blood cells and cause internal hemorragins. The different substances are not uniformly present in all snake venom, but vary with the species and the individual snakes within a species. Venom retains digestive powers; injected into a prey animal it may shorten the usual days-long digestive process of a snake by more than half. Less than one-third of the 2,500-3,000 living species of snakes are classified as venomous, and less than 300 species are fatal to humans. In the United States, more than twice as many people are killed by bees, wasps, and scorpion stings as by snake bites. Keith 3 There are four basic kinds of snake movement: Lateral (horizontal) undulation, conceltina movement sidewinding and rectilinear. Lateral undulating, also called serpentine movement is the most common form and is used by all snakes. By alternately contracting and relaxing muscles down each side of the body, the snake forms itself into a number of rearward-moving horizontal waves. While doing so, the snake maneuvers its body so that the rear of each backward moving wave pushes against something resistant. In concertania movement, also called earthworm movement, the snake anchors the forepart of its body and pulls the rest of its body behind it in the form of hoizontal curves; it then extends out the forepart of its body, anchors it, and repeats the process. Sidewinding is employed on soft sand or other surfaces that offer no resistance or slip. In sidewinding the snake loops its body into an S-shape, with only two points of its body coming in contact with the surface of the ground. It then progressively shifts the two contact points back along the body consequently propelling its body forward. Rectilinear, or caterpillar, movement involves a sliding of the skin back and forth over the body musculature and is therefor possible only in those kinds of snakes, such as rattlesnakes and boas, which do not have the skin tightly attached to the underlying musculature. The ribs remain essentially motionless, and the scales only provide body-to-ground friction. Keith 4 The vast majority of snakes lay