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Evolution Of Sharks Essay

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How much do you know about our “living fossils?” Sharks have hardly evolved over time. In reality, the change has been very little in 425-450 million years. There are as many as 400 known shark species.

Classifying sharks can be tricky. There are eight orders of sharks based on evolution; Squatiniformes, Pristiophoriformes, Squaliformes, Hexanchiformes, Carcharhiniformes, Lamniformes, Orectolobiformes, and Heterodontiformes. Below is a dichotomous key showing how taxonomists categorized sharks.

Image belongs to: SharkSidercom

Sharks are part of the chondrichthyes family, and the subclass of elasmobranchii and euselachii. They are classed based on whether their body is flattened, snout size, number of gill slits, has a dorsal fin, mouth placement, eye placement, and if their eyelids are nictitating.

It can be difficult to identify sharks from fossils. Sharks are made out of cartilage which …show more content…
Scientist also believe the first sharks were much faster. Today’s sharks have a brain larger than the ancestors. At one point, all sharks were freshwater creatures. Today, there are very few sharks who can survive freshwater.

Throughout evolution, some characteristics remained the same. For instance, their skeleton design. Their body shape and size is to allow for protection and movement. Sharks must be constantly moving to breathe. Typically, females are much larger than male sharks. As well, their eyes can adapt to low light environments.

Sharks have a high migratory pattern and are solitary hunters, thus research is done about sharks who we think are dangerous. A study at Florida Atlantic University discovered that hammerhead sharks had amazing peripheral vision. They can see a full 360 degrees around their heads! It was stated in The Journal of Experimental Biology that they have a great sense of depth perception and forward stereo

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