Say the word "shark" and the first image most people conjure up is a Jaws-inspired white shark devouring unsuspecting bathers while well meaning authorities and scientists helplessly stand by. Sharks are one of the most feared creatures on Earth. The seas only other creatures with capability of consuming a human, killer and sperm whales, are not normally considered threats to man. Sharks, on the other hand, have been documented attackers of humans around the world throughout recorded history and have remained relatively immune from human intervention. Even the fiercest of terrestrial predators, the large cats and bears, are extremely susceptible to a rifle and problem animals have simply been eliminated. Sharks have a history twice as long as that of dinosaurs. Fossilized teeth, fin spines, and sharks" eggs found in marine sediments tell us that today's sharks are not much different from their ancient ancestors (Garrison 2000). Even so, people demand their extermination. How can we demand such a request from a species that has been swimming the ocean for at least four hundred and fifty million years? They have existed before dinosaurs and even before their were trees. Such an existence does not deserve to be eliminated by a short-lived species such as ours just because of our myths of ignorance. Their existence as survivors of long evolutionary process shows a definite trait for endurance in predatory and survival instincts. A brief look at their sensory system and behavior will be covered in this report.
Body.
General Information.
Sharks are in the class of Chondrichthyes, which are species that have a skeleton made of a tough elastic tissue called cartilage. Though there is some calcification in the cartilaginous skeleton, true bone is completely absent from this group (Garrison 2000). The Chondrichthyes consist of two groups: The Elasmobranchii (sharks and rays) and the Holocephali (chimaeras) (Gold and Springer 1989).
