Organism Physiology Paper

The organism that will be getting discussed today will be sharks mainly the bull shark. Sharks are one of the oldest animals in the world dating back to almost 455 million years ago. Sharks have went through a lot of changes over the long existence of their species for instance where the mouth is on the head the original sharks are too have their mouths on top of their heads while sharks now have their mouths on the bottom of their heads, early sharks were also near shore predators instead of the fast swimming off shore predators that we have now. One of the ancient sharks was Cladoselache shark which did not have the tooth-liked scales that provided protection like most ancient and modern sharks have and had. These kind of shark did not have the claspers on the male sharks that are used to mate with female sharks even without having these two key parts to the shark this species of shark survived for over a million years. The modern sharks of the day did not become to be until about 65 million years ago when another global catastrophe happened that destroyed a mass number of species to include the dinosaurs and the sharks that survived this include the species of sharks we have today. Most of the sharks up to this point have been predators but about 65 to 35 million years ago there was group that evolved into a breed of filter feeding sharks that came about on earth. The most common today are the Whale shark and the Basking shark. One of the most interesting modern sharks is the bull shark because it has evolved to be able to breath in fresh and salt water and being able to do this is called osmoregulation. Doing this allows for the bull shark to be able to maintain a constant concentration of water in its body even when the outside environment causes it to lose or gain water. The bull sharks environment normally is the ocean where there has an abundant of salt in the water that is the reason that other sharks are able to live in the ocean because they are constantly getting the salt that they need to be able to survive if a different kind of shark was put into freshwater they would end up drowning because sharks other than the bull shark are unable to control how their bodies use the salt in their bodies. The bull shark uses its kidneys to be able to regulate the salt in its body and all sharks need a certain amount of salt to be able to stay alive they do this by removing less salt and more urea from their bloodstream through urination essentially reversing the normal marine shark method of osmoregulation. Doing this allows for bull sharks to be able to live in freshwater and estuaries. With being able to do this and live in freshwater beings this kind of shark into contact with humans much more because the sharks are more likely to be in the same area of a human in estuaries than in the ocean because people spend more time in estuaries.

Sharks have made a lot of changes with being one of the oldest animals on earth. Being on the earth for over 500 million years a species has to go through the need changes or else they will go extinct. These animals have been as big as 50 feet long and as long as just inches long and this just shows how one kind of animal can be so different depending on the time that they were alive and what kind of predators and prey were around for them to eat or be eaten by. The bull shark is a very different kind of shark because it is able to go into freshwater unlike any other kind of shark throughout history and that makes it very unique. This shark might be just the next step for the sharks in their evolutionary trail and if this is it then our world is just going to get that many more changes as it gets older.

References
450 Million years of Sharks. (2013). Retrieved from https://www.sharksavers.org/en/education/biology/450-million-years-of-sharks1/
How Bull Sharks Can Live in Both Ocean and Fresh Water. (2013). Retrieved from https://www.sharksavers.org/en/education/biology/how-bull-sharks-survive-in-fresh-water/