What is a Shark? How Do I Identify a Shark?

You have probably heard a lot about sharks but, instead of convincing you, most of them confused you on what a shark really is. Sharks are not always what people portray them to be. In fact, they are sweet creatures if you get to know them. That’s why we would fill you in with all the fascinating things about sharks in this article.

So, what is a shark? Sharks are species of fish. They belong to the class of fish “Chondrichthyes” (Cartilaginous fish) and the subclass “Elasmobranchii.” This class also includes skates and rays. Species that fall into this subclass have a cartilaginous skeleton and not bones. The fish species in this subclass have five to seven gills on each side of their heads that they use in filtering oxygen from the water.

With the varying species of sharks in the ocean, you may find it difficult to identify certain species. But, don’t worry sharks have some characteristics they share by which you can easily identify them. Of course, these are what made them sharks in the first place!

How Do I Know Sharks?


Sharks have varying colors ranging from gray to cream, slate, yellow, brown, or blue. They usually have patterns or spots all over their back. These features depend upon their species.

Most sharks have the same features apart from hammerheads whose head looks like a double edge hammer. Another exception is wobbegongs that have skin flaps and skin coloration that matches the seafloor.


Sharks inhabit seas and oceans globally, most especially in warm waters because they prefer it. Some sharks are pelagic, meaning they live in the open ocean. Examples are the basking shark, the great white shark, etc.

Some are benthic sharks, meaning they live on the ocean floor. Examples are angel sharks, wobbegongs, and horn sharks, while others prefer to stay deep in the middle of the water.

Shark’s Anatomy


Sharks do not have bones. Their skeleton is made up of connective tissues and cartilages that allow flexibility and durability. Cartilage is about the average normal density of bone. Thus, the absence of bones in their skeleton reduces the skeleton’s weight and saves energy.

Fun fact: Because of the absence of ribcages in sharks, they can crush under their own weight when on land.


Like that of rays and skates, the jaws of sharks do not attach to their skull. Instead, their jaws have small layers of hexagonal plates known as “tesserae.”

Tesserae is a block of calcium salts that gives the jaw the same strengths found in other animals’ bony tissue.

The majority of sharks only have one layer of tesserae. But large specimens like the great white sharks have about two or three layers, unique to their body size.


Sharks have elongated fins that are guided by ceratotrichia, which is an unsegmented ray. Generally, sharks have eight fins.


The essence of tails in sharks is to provide thrust and acceleration. Therefore, the acceleration rate solely depends on the shape of the tail. Sharks have heterocercal caudal fin whose dorsal part is visibly larger than the ventral region.

The reason why this happens is that their vertebral column leans more towards the dorsal region. This gives them more flexibility to move.


Unlike most animals, sharks’ teeth are fixed directly in the gum instead of the jaw. As a result, they shed teeth throughout their lifetime. This is why most shark’s fossils are teeth.

Their replacement teeth usually grow in the jaw and then move forward when replacing the old teeth.

Sharks lose up to about 30000 teeth throughout their lifetime. The rate of changing teeth varies per species, but it mostly happens averagely once in 8 to 10 days.

Generally, sharks replace their teeth one at a time. However, the cookiecutter shark is an exception as it replaces its entire teeth row all at once.

The shape of sharks’ teeth depends on their diet. Hence, sharks that feed on crustaceans and mollusks tend to have dense flattened teeth, while the species that prey on fish have needle-like teeth.

And, others that feed on larger prey, like mammals, have triangular upper teeth for cutting and pointed lower teeth for holding their prey.

Dermal denticles

Sharks’ dermal corsets are complex and contain flexible collagenous fibers positioned as a helical network enveloping their body. This dermal corset works as a support for their swimming muscle, thereby conserving energy while aiding seamless movement.


Sharks are social. Most sharks like to form large groups, while others prefer to be solitary. The reason why some want to move in groups is still unclear because sharks do not need protection from predators. Although, it is possible that they enjoy the company of their peers.

Sharks also show a level of intelligence. The most social shark is the hammerhead shark. Sharks can also communicate with each other through body movements.

Can I Encounter a Shark Sleeping?

If you ask if sharks sleep like every other animal sleep, then no, they do not sleep, but they do engage in a period of rest especially during the day.

Some sharks are ram ventilators, which means they have to draw water through their mouth and force it out through their gills to stay alive while some possess what we call buccal pumping.

However, whichever method they chose to remain alive, sharks definitely have periods when all they do is just rest.

Sharks don’t have eyelids, so their eyes remain open all the time, and they can still detect movement from other creatures around them.

Sharks that can rest while remaining stationery includes nurse sharks, lemon shark, and wobbegong sharks.

While you can encounter sharks resting, this is not an opportunity to get too close to it or try something funny. This is because they are aware of their surrounding even when resting.

If I Bleed in the Water, Will I Attract Sharks?

Sharks’ olfactory system is far more sensitive than that of humans. Their nostrils located under their snout is mainly for smelling and not for breathing, which makes it very sensitive.

Sharks can detect the smell from a distance, including blood, but that doesn’t mean they want to rush to the place and attack like the common myth.

Will Sharks Attack Humans?

Though sharks have a bad reputation of being the vilest predator, and even got a role as the scary villain in movies like “Jaw”. Sharks do not attack humans on purpose. Humans are not part of their diet.

Out of over 400 species of sharks globally, only about six species have been involved in attacking humans. Generally, they only attack humans out of curiosity or mistook them for their prey.

Some also attack humans when they feel threatened but other than that; sharks do not hunt or attack humans on purpose.

What Can Sharks Eat?

Sharks’ diets vary. It all depends on the species, but one thing that is common to all is that they are all carnivores.

Sharks such as mako sharks, hammerhead sharks, tiger sharks, great white shark are fierce predators that feed on squids, fish, and some other marine mammals.

Some others, like angel sharks, horn shark, wobbegong, prefer to feed on shellfish like clams and crabs.

While others are filter feeders that like to feed on plankton and small animals in the water. Examples are megamouth, basking shark, and whale shark.

What Can Sharks Do?

There are many things shark can do, but the most interesting fact about them is that they can show intelligence. They can learn at a similar rate to birds and rats.

Can a Shark’s Skin Cut You?

Sharks skin are called dermal denticles, and the reason why they are called dermal denticles is that their skin looks like small skin teeth under a microscope. Shark’s skin can cut you if you accidentally bump into it, or it attacks you. Their skin is rough and as sandpaper feel, which is very sharp.

Are Sharks’ Meat Available for Food?

Yes, sharks can be eaten. Their meat is very legal in some countries like Japan, Korea, Australia, Sri Lanka, and the united states. Sharks have much meat due to their body weight.
Humans have been eaten sharks’ meat for centuries now before the latest research. So, before you consume a shark’s meat, you need to understand that sharks’ flesh contains mercury due to pollution in their environment.

Can Sharks See?

There have always been many myths surrounding sharks’ vision. Some believe that sharks can’t see reason they mistake humans for prey, or they can’t see because of their great sense of smell.

However, researchers found that most sharks can see clearly. Sharks can only see in monochromatic, which means they only see in black and white. So, in plain terms, sharks are color blind. But, that aside, sharks can see in low light and see a more focused image.

Do Sharks Eat Humans?

Sharks do not feed on humans. However, this doesn’t mean that they won’t bite humans.

The thing is that sharks do not bite humans to feed on them. That has never been their primary aim because humans’ meat doesn’t contain enough fat for them.

They attack humans when they feel threatened or mistake them for their prey. Most times, sharks bite once and retract.

Just a single bite from a shark can cause excessive bleeding that could lead to death. But they do not bite humans for food at all.


If you read this post to this point, I believe you have more than enough knowledge about sharks now that can last you a lifetime. Sharks are beautiful creatures, contrary to what you might have heard about them. They are a species of fish and a whole lot of other things.