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.

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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.

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The vast majority of snakes lay