What is a Shark?
A Shark is a kind of Cartilaginous Fish. That is, instead of bones, they have softer stuff called Cartilage. There are other kinds of cartilaginous fish too, for example the rays and skates. The most common types of cartilaginous fish are sharks and rays. Like most other fish, Cartilaginous fish mostly Have gills instead of lungs, breathing water instead of air.
Sharks have replaceable teeth, and can grow many thousands in their lifetime. For this reason, some types of shark that are now extinct are known only from their teeth. An example is the largest ever shark – in fact, the largest ever cartilaginous fish, the Megalodon.
What kinds of sharks are there?
The scientific name for the sharks is Selachimorphs. There are 8 different groups of sharks, called “orders”.
- The Hexanchiformes have six or seven gill slits on each side. Most sharks have only five.
- The Squaliformes have an extra fin on top, and cutting teeth at the top and the bottom.
- The Pristiophoriformes are the Sawsharks – not to be confused with the Sawfish mentioned above! Sawsharks use their toothed snout to hack and slash at the fish they are eating. All species of sawsharks are in danger of extinction.
- The Squatiniformes look like rays. However, their gills are on the sides of their heads, like all other sharks. They are also called Angel Sharks.
- Heterodontiformes means “Different kinds of teeth”, and sure enough, these sharks have a variety of teeth so that they can grasp and crush shellfish.
- The Orectolobiformes are commonly called “Carpet Sharks” because their skin has nice patterns on it. The world’s largest fish, the Whale Shark, belongs in this group.
- The Carcharhiniformes are the most diverse group of sharks, with over 270 species. They have an extra set of eyelids to protect their eyes.
- The Lamniformes, also called Mackerel sharks, include the biggest cartilaginous fish ever, the Megalodon, as well as the most famous type of shark, the Great White Pointer. It also includes the harmless and very rare Megamouth Shark.
Are Sharks Really Dangerous?
Actually, people are more dangerous to sharks than the other way round. Did you know that more people are killed each year by dogs than by sharks? Here are some reasons why sharks are not as dangerous as people sometimes think.
- Many types of sharks just don’t eat people-sized food. For example, the world’s largest shark, the Whale Shark, gets all its food from plankton and tiny shrimps.
- Even sharks with a reputation for being dangerous are less dangerous than we think. For example, the Great White Shark, although it is the world’s largest predatory fish, has only killed 31 people in the Mediterranean in the past 200 years. In fact, we aren’t even healthy food for the Great White Shark – we aren’t good for its digestion.
- Even when a person is attacked, the victim’s friends can often help him or her escape.
- We are able to warn each other about sharks, and we’ve invented shark nets, shark cages and shark repellents to protect ourselves.
On the other hand, humans are very dangerous to sharks. Shark fishing is a booming industry, and many governments don’t watch carefully how many sharks are being caught.
- “Shark’s fin soup” is a delicacy in some cultures. Fishermen will catch a live shark, cut off its fin, and release the live shark back into the water, where it will die of suffocation or from being attacked by predators.
- Some people believe that shark cartilage has healing powers, although there’s no evidence at all that this is true.
Because of this, the number of sharks is dropping greatly in many places. We are catching too many sharks. They cannot stand it much longer.
What is the world’s largest shark?
The world’s biggest shark is in fact the world’s biggest fish – the Whale Shark. Although it’s so big, it’s very harmless – unless you are a tiny plankton or miniature squid! I eats only very small creatures, but grows up to 12 metres (about 40 feet) long, and weigh around 12000 kg, or 26000 pounds!
The world’s largest ever shark was the Megalodon or Megatooth Shark. It was similar to the famous Great White Pointer, but three times as big! At 18 metres (60 feet) long, its main food would have been Whales of various types.