Evolution of Snakes

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The Evolution of Snakes
Rafferty Crawford
BIO/101
July 17, 2012
Peter Karanja
The Evolution of Snakes
Snakes are a diverse group of squamates that include about 2900 species of boas, colubrids, pythons, vipers, blind snakes, mole vipers, and sunbeam snakes (Pickrell, 2010). Snakes, like all living things, are a product of the process of evolution. Evolution allows species to change over time in response to environmental factors to produce entirely new species. As diverse as they are today, we still know very little about the ultimate origin of snakes. It is clear that these cold-blooded legless creatures evolved from its four-legged reptilian ancestors that appeared over 100 million years ago (Van Devender, 2012). First, by the skeletal structure of the snake being so delicate, fossilization is merely difficult. Second, since most of the fossil material found consisted mostly of vertebrae, this made it difficult to decipher from other relatives. Most scientists believe that snakes evolved from land lizards, but the findings indicated that snakes originally evolved from marine lizards (Pickrell, 2010). THE ANATOMY OF A SNAKE • [pic]

The internal organs of most snakes have changed over the course of their evolution to fit their slender form (Reptile Expert, 2011). Snakes lack a diaphragm so they use their own muscles to expand the ribs to drawn in air. Air then flows through the glottis, connected to the trachea, then passing through the right lung. The diagram shows two, but most snakes only have one lung to make space within their slender body and because the left lung serves no purpose. Their stomachs are elongated for space as well and contain internal folds to increase the surface area for absorption and digestion, the intestines are less coiled, and the kidneys are elongated as well (Reptile Expert, 2011). A process over millions of years caused snakes to become burrowers (Van Devender, 2012)....
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