Biology and Evolution: The Case of Snakes

Biology and Evolution: The Case of Snakes

Snakes are incredible creatures. They have evolved very unique features that have allowed them to adapt to a wide number of environments. Snakes can be fond in some of the hottest deserts, the densest swamps, and even on the ocean floor. Part of their success comes from the physiological evolution of their organs and anatomical structures that has provided for their evolutionary success.

The snake's anatomy is truly unique. It is a reptile that has elongated its body and internal organs by sacrificing its legs. All of the major organs of the snake have been elongated to allow for a tubular body shape that has helped re-engineer the way a snake moves. The entire skeleton has morphed in order to account for this evolutionary process that allowed snakes to succeed in a wide variety of environments. According to the research, a snake's skeleton is "a complicated-architecturally and functionality -- skull at its head is followed, to the tail, by at least five divisions of vertebral structures" (Cates, 2012). Ribbed and unribbed vertebrae interlock all the way down through the length of the snake's body. Ribs help protect the elongated organs. The snake's respiratory system has evolved into a long, complicated string of organs. It begins with the moveable glottis to help avoid breathing in parts of the prey in the mouth that leads to a windpipe. The windpipe "extending from the glottis, divides into two bronchial tubes, each leading to the lungs; the right is pulmonary and the left is secondary, considerably smaller and either non-functional or only marginally so" (Cates, 2012). This allows for one lung to take up more space in the small body cavity. The snake smells through its two pronged tongue which collect and distribute scent particles to the vomeronasal, which is its primary sensing organ (Cates, 2012). Its stomach is small and elongated, yet allows for massive increases of size in order to be able to digest large prey whole. This leads downwards towards the digestive tract, which is also elongated to fit the tubular form of the snake. The two kidneys have also flattened and extended in size to fit the modal for snake anatomical structures.

To further assist in this type of movement, snakes have lost all their limbs and changed their bone structure through the long and arduous process of evolution. Research shows that they are a distant relative of the reptiles that once dominated the earth. The are not descendants of the dinosaurs, but rather a cousin, as snake fossils have been found to date back to the period of the dinosaurs (Karbahl, 2012). The snake's distant ancestors did once have legs. Snakes today still have tiny claws or toe like structures that are found "protruding from either side of the cloaca…these are remnants of the legs that their ancestors once had" (Karbahl, 2012). This shows clearly their evolutionary process. From their legged ancestors, snakes evolved to move without limbs, allowing for greater flexibility and dexterity. However, the presence of these claws are signs of vestigial structures, or parts of the body that are no longer needed which "are leftovers from a previous form of the species before speciation occurred" (Scoville, 2012). The bone structure of modern snakes has also been adapted from their ancient ancestors from the distant past. Snakes head and teeth structure allow for it to take on prey much larger than the size of its own mouth. The bottom jaw is attached by flexible ligaments allowing for a wide mouth than can extend fitting prey. Here, the research states that "the right and left lateral portions of the lower jaw attach to each other at the lower snout by elastic cartilaginous tissue that enables them to move freely and independently" (Cates, 2012). This amazing mouth structure has been evolutionary successful because it allows snakes to go after all sizes of prey, despite their own smaller sizes.