Evolution Of Sharks Essay

It has been noted that during breeding season, sharks will fast for an extended amount of time, and live off of lipids stored in their livers. Sharks do not necessarily require mating in order to reproduce, this type of reproduction is referred to as “parthenogenesis”. Shark’s senses are highly developed, most particularly their sense of smell which allows them to detect a subtle smell to its exact source. Shark’s sense of sight and hearing, although not quite as developed as their sense of smell, is also a helpful aid in the capture of prey as they can see shadows in both dark and well lit waters, as well as hear “low frequency” noises and have acquired directional hearing. Another useful sense of sharks is their ability to feel electrical …show more content…
Aidan Martin of ReefQuest explains the evolution of sharks. Sharks are one of the oldest creatures, preceding dinosaurs by about 200 million years according to Martin. Often fossilized shark teeth, and scales must be used to study the evolution of sharks because sharks do not leave behind bones to study, which makes it extremely difficult for researchers to determine much about these prehistoric sharks. The earliest sharks date back to 420 million years ago, based off of scales found in Siberia. Not much is known about sharks from this time period. Yet, Martin states, “Fortunately, the shark fossil record becomes richer and more varied from the Devonian Period onward”. The earliest evidence of sharks from the Devonian Period dates back to 400 million years, located in modern day Europe. These sharks, known as Leonodus, are thought to be from a group of freshwater sharks based on their teeth shape and size. As a group sharks exhibited their remarkable adaptability by surviving many environmental pressures such as changes in sea level, and ocean circulation. Martin goes on to say, “Each time their environment was radically altered, shark lineages responded with a spectacular flowering of diversity, enabling them