Organism Physiology

Organism Physiology

Vanessa Jenkins

BIO/101

March 16, 2015

Keidra Davis

Organism Physiology

The organism that I will be discussing will be the bull shark. Sharks are the oldest animals in the world. They back date to 455 million years ago. The sharks have went through a lot of changes over the long existence of their species. The mouth was on top of the heads in the beginning and now the mouth is on the bottom of the head. Sharks used to be near shore predators but now they are fast swimming off the shore predators.

One of the ancient sharks was the Cladoselache shark. This shark does not have the tooth liked scales that provided protection like most ancient and modern sharks have now. These kind of sharks does not have claspers on the male sharks that use to mate with female sharks. Without these two key parts to the shark this kind of species survived for over a million years.

The modern shark today came into existence over 65 million years ago when the global catastrophe happened. When this happened it destroyed a large number of species which included other species such as the dinosaurs. The sharks survived and this include the sharks that we have today. The most common today are the Whale shark and the Basking sharks. The most interesting shark is the bull shark because it has evolved to be able to breathe in fresh and salt water and this is called osmoregulation. Doing this allows the bull shark to be able to maintain a constant concentrations of water in its body even when the environment causes it to lose or gain water. Most sharks have been predators for over 65 million years.

The environment of the bull shark is normally in the ocean where there is a large amount of salt in the water. This is the reason that other sharks are able to live in the ocean. They are constantly getting the salt that they need to be able to survive if a different kind of shark was to be put into the freshwater. These sharks probably would end up drowning because sharks other than the bull sharks are unable to control how their bodies use salt. The Bull Shark uses its kidneys to regulate the salt in its body. Just like all sharks need a certain amount of salt to be able to stay alive. This is done by removing less salt and more urea from their bloodstream through urinating. This is essentially reversing the normal shark method of osmoregulation. When this is done it allows the Bull Shark to be able to live in freshwater. Being able to live in freshwater will allow the sharks to come in contact with humans more because the sharks are more likely to be in the same area as human’s estuaries than in the ocean. Humans spend more time in the estuaries.