Sharks

Sharks are a type of fish because they breathe with gills. 

Sharks live in every ocean on the planet which is why they have over 500 species of shark.Sharks have eight orders of classification depending on their physical characteristics.Sharks are cartilaginous.What makes sharks different from fish is that their skeleton is made from cartilage not bone.They are also different from bony fish because they have eyelids.

Another thing that makes sharks different from fish is their scales.Sharks have dermal denticles also called placoid scales,which are smooth and help them move quickly through water.Fish have,rough scales.

Unlike fish, sharks can only swim forward.That is because their fins are stiff and cannot be controlled by muscles.Sharks stay buoyant because of their light weight cartilage skeletons.They also have really oily livers which helps them stay balanced in deeper waters.

An average sharks 40-45 teeth in up to seven rows.Sharks lose teeth regularly and can go through 30,000 teeth in their lifetime.Sharks have been living in Earth’s oceans for 450 million years.The smallest shark is the dwarf lantern that only grows to six inches and the largest one is 41.5 feet.