What makes sharks unique

Based on fossil scales found in Australia and the United States, scientists hypothesize sharks first appeared in the ocean around million years ago.

Vertebrae contain concentric pairs of opaque and translucent bands. Band pairs are counted like rings on a tree and then scientists assign an age to the shark based on the count. Thus, if the vertebrae has 10 band pairs, it is assumed to be 10 years old. Recent studies, however, have shown that this assumption is not always correct. Researchers must therefore study each species and size class to determine how often the band pairs are deposited because the deposition rate may change over time.

Determining the actual rate that the bands are deposited is called "validation". The blue shark displays a brilliant blue color on the upper portion of its body and is normally snowy white beneath. The mako and porbeagle sharks also exhibit a blue coloration, but it is not nearly as brilliant as that of a blue shark.

In life, most sharks are brown, olive, or grayish. Whale sharks are the biggest fish in the ocean. They can grow to Basking sharks are the world's second largest fish, growing as long as 32 feet and weighing more than five tons.

A shark's spiracle is located just behind the eyes which supplies oxygen directly to the shark's eyes and brain. Bottom dwelling sharks, like angel sharks and nurse sharks, use this extra respiratory organ to breathe while at rest on the seafloor. It is also used for respiration when the shark's mouth is used for eating. Mako sharks have very pointed teeth, while white sharks have triangular, serrated teeth.

Each leave a unique, tell-tale mark on their prey. A sandbar shark will have around 35, teeth over the course of its lifetime! Sharks exhibit a great diversity in their reproductive modes. There are oviparous egg-laying species and viviparous live-bearing species. Oviparous species lay eggs that develop and hatch outside the mother's body with no parental care after the eggs are laid. Last updated by Office of Communications on July 14, Feature Story National. Sharks do not have bones.

This is another great example of why Ecosystem Based Management, one of the core strategies in our National Ocean Policy , is the right tool for the job. Click here to write your Governor today to urge them to support this policy, and healthy oceans for all. Will you be a part of this movement by considering a contribution today? Join us. Follow CLF. Focus Areas Oceans. Oceanic shark and ray populations have declined by 71 percent in the last 50 years and more than shark and ray species are now threatened with extinction.

People are working hard around the world to save sharks and you can be part of the solution too! Here is what can you do to help protect sharks:. There are online sustainable seafood guides for many countries and they are easy to use:. Your email address will not be published. Leave this field empty. Previous article. Top Facts About Sharks. There are over species of sharks. The largest species of shark grows up to 18 meters long.

The smallest shark species is smaller than a human hand! Sharks are vital for healthy oceans. Why does phytoplankton matter? It produces the oxygen that we breathe! Some sharks get through more than 20, teeth in their lifetimes.

Some sharks glow in the dark. One of the weirdest facts about sharks is that some of them glow in the dark! Sharks can travel thousands of miles each year. Sharks are found in almost every ocean habitat. You can swim with sharks at destinations around the world. Some sharks are warm-blooded, just like us.

Sharks have different personalities, just like us. Sharks support our wellbeing. Sharks have 2 more senses than humans. Sharks have existed in our oceans since before the dinosaurs Sharks have been around in the oceans for over million years! Are sharks man-eaters? No, they rarely attack humans. All of which demonstrates how infrequently humans are bitten by sharks.

Sharks can live for more than years. Around million sharks are killed globally each year. Three hundred species of sharks and rays are threatened with extinction.