Sharks, LittleJerry, CC BY-SA 4.0 , via Wikimedia Commons

Shark: Everything You Need to Know About Selachimorpha


Sharks have long captivated our curiosity and fears, thanks to their significant role in marine ecosystems, ancient evolutionary lineage, and their portrayal in popular media. This article provides an overview of shark biology, ecology, behaviour, and conservation, highlighting the importance of a deeper understanding of these apex predators.

What are Sharks

Sharks (Selachimorpha) are a group of cartilaginous fish that have played a significant role in marine ecosystems for over 420 million years. With more than 500 species of sharks inhabiting a wide range of aquatic environments, their diversity and evolutionary success are truly remarkable. This article aims to provide an in-depth understanding of shark biology, ecology, behaviour, and conservation, unravelling these fascinating creatures’ mysteries.

Biology and Evolution

Sharks belong to the class Chondrichthyes, which also includes rays and chimeras. They are characterized by their cartilaginous skeletons, as opposed to the bony skeletons of other fish. This lighter, more flexible skeleton allows for greater maneuverability and speed in the water. Sharks have evolved several unique characteristics that contribute to their success as predators, including their streamlined body shape, numerous sharp teeth that are constantly replaced, and various sensory adaptations.

Sensory Adaptations

Sharks possess sophisticated sensory systems that allow them to detect and respond to their environment. Their keen sense of smell is well-known, with some species able to see as little as one part per billion of blood in the water. Additionally, sharks have excellent eyesight in low-light conditions, with specialized cells called rod cells enabling them to see in the dark.

Another remarkable adaptation is the lateral line, a series of neuromasts that run along the length of the shark’s body. These sensory organs can detect minute pressure changes in the surrounding water, allowing sharks to sense the movement and location of prey, even at a distance. Sharks also possess electroreception, a specialized system that enables them to detect electrical fields generated by the muscle contractions of prey. This ability, known as the ampullae of Lorenzini, provides sharks with an additional tool for locating and capturing prey.

What Do Sharks Eat?

Sharks are carnivorous and occupy various levels of the food chain, depending on the species. Their diets range from plankton (whale sharks) to large marine mammals (great white sharks). Many sharks are opportunistic feeders, consuming whatever prey is available in their habitat. Shark feeding strategies vary as well, with some species, like the nurse shark employing suction to draw in prey, while others, like the great white shark, use powerful bites to subdue their quarry.


Shark reproduction can be classified into three primary modes:

  • Oviparity (egg-laying)
  • Ovoviviparity (live-bearing with a yolk sac placenta)
  • Viviparity (live-bearing with a placental connection)

The gestation period varies between species, ranging from a few months to two years. Some species, such as the sand tiger shark, practice intrauterine cannibalism, in which the developing embryos consume their siblings before birth.

Behaviour and Social Structure

Shark behaviour is diverse and complex, influenced by factors such as species, habitat, and availability of prey. While some species are solitary, others, like the scalloped hammerhead, form large schools. Migratory patterns are also observed in certain species, such as the great white shark, which travels long distances to access seasonal food sources.

Shark Conservation and Human Interaction

As apex predators, sharks play a crucial role in maintaining the balance of marine ecosystems, and their decline can have cascading effects throughout the food chain. Shark populations worldwide have been negatively impacted by human activities, including overfishing, habitat destruction, and the shark fin trade. It is estimated that up to 100 million sharks are killed yearly, primarily for their fins, which are used in shark fin soup – a luxury dish in some cultures.

Conservation efforts are underway to protect shark populations and their habitats. Several countries have implemented shark finning bans, while some areas have established shark sanctuaries to safeguard critical habitats. Public awareness campaigns also aim to dispel misconceptions about sharks and promote a better understanding of their ecological importance.

Shark Research

Ongoing research is necessary to improve our understanding of sharks and better inform conservation strategies. Key areas of study include shark behaviour, ecology, and genetics. Researchers utilize various methods to study these elusive creatures, such as tracking devices, underwater cameras, and genetic analysis. These efforts contribute to a growing body of knowledge that can help guide future management and conservation initiatives.


Sharks are diverse and fascinating creatures that have captivated our imagination for centuries. Their unique adaptations, complex behaviours, and ecological significance make them essential to our ocean ecosystems. As we continue to uncover the mysteries of these ancient predators, we must also recognize our responsibility to protect them and the habitats they rely on for survival. By fostering a greater appreciation and understanding of sharks, we can help ensure their continued existence for generations.

Frequently Asked Questions

Are Sharks Mammals?

No, sharks are not mammals. They are a type of fish belonging to the class Chondrichthyes.

Do sharks have bones?

No, sharks do not have bones. They have a cartilaginous skeleton, which is lighter and more flexible than a bony skeleton.

Do sharks sleep?

Sharks do not sleep in the same way humans do. They have periods of rest and reduced activity, but they must keep swimming to maintain oxygen flow over their gills.

Are sharks fish?

Yes, sharks are a type of fish belonging to the class Chondrichthyes.

Do sharks lay eggs?

Some shark species lay eggs (oviparous), while others give birth to live young (viviparous or ovoviviparous).

How many teeth do sharks have?

The number of teeth in a shark’s mouth varies by species, but most have multiple rows of teeth that can number thousands over their lifetime.

Do sharks have tongues?

Sharks have a small, flat structure called a basihyal, which is not an actual tongue and has limited function.

How long do sharks live?

Shark lifespans vary by species, ranging from 10-15 years for some small species to over 100 years for the Greenland shark.

How many people die from sharks a year?

On average, around ten people die from shark attacks each year.

How many shark attacks per year?

There are approximately 80-100 unprovoked shark attacks reported worldwide each year.

How big is a great white shark?

Great white sharks can grow up to 20 feet (6 meters) in length and weigh up to 2.5 tons (2,268 kg).

How do sharks mate?

Shark mating involves the male shark inserting one of its claspers (modified pelvic fins) into the female’s cloaca to transfer sperm.

How many sharks are killed a year?

It is estimated that up to 100 million sharks are killed yearly, primarily for their fins.

How many species of sharks are there?

There are over 500 known species of sharks.

What do great white sharks eat?

Great white sharks primarily eat seals, sea lions, fish, and other marine mammals.

Where do sharks live?

Sharks inhabit a wide range of aquatic environments, from shallow coastal waters to the deep sea and even freshwater systems.

How big is a whale shark?

Whale sharks can grow up to 40 feet (12 meters) in length and weigh up to 20.6 tons (18,700 kg).

How long have sharks been around?

Sharks have been around for over 420 million years.

What is a group of sharks called?

A group of sharks is called a shiver, school, or shoal.

What is the biggest shark?

The whale shark is the largest living shark species.

Are sharks fish or mammals?

Sharks are fish belonging to the class Chondrichthyes.

Are there sharks in the Mediterranean Sea?

Yes, there are several species of sharks found in the Mediterranean Sea.

Can sharks smell blood?

Yes, sharks have an acute sense of smell and can detect minute amounts of blood in the water.

Can you eat sharks?

Shark meat is consumed in some cultures, but many species are threatened by overfishing, and consuming shark meat can pose health risks due to high levels of mercury.

Why do sharks attack humans?

Shark attacks on humans are rare and usually a case of mistaken identity, as sharks may mistake a human for their natural prey, such as seals or fish. In most cases, sharks release the human once they realize the mistake.

Are great white sharks endangered?

Great white sharks are listed as “Vulnerable” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

Are hammerhead sharks dangerous?

Hammerhead sharks are generally not aggressive toward humans, but some larger species, like the great hammerhead, have been involved in a few attacks.

Are whale sharks dangerous?

Whale sharks are not dangerous to humans; they are filter feeders and pose no threat.

Do sharks eat dolphins?

Sharks may occasionally prey on dolphins, particularly young or injured individuals, but dolphins are not a primary food source for most shark species.

How fast can a shark swim?

Shark swimming speeds vary by species, with the shortfin mako shark being one of the fastest, capable of reaching speeds up to 45 mph (72 km/h).

How long do great white sharks live?

Great white sharks have a lifespan of around 30 years, although some individuals may live longer.

How many shark species are there?

There are over 500 known species of sharks.

Where do great white sharks live?

Great white sharks have a wide distribution, inhabiting temperate and subtropical coastal waters worldwide.

Are sharks blind?

Sharks are not blind; they have well-developed eyesight, particularly in low-light conditions.

Are there sharks in Lake Michigan?

There are no sharks in Lake Michigan or any of the Great Lakes, as they are freshwater systems.

Do orcas eat sharks?

Orcas have been known to prey on some shark species, including great white sharks.

Do sharks have scales?

Sharks have a unique type of scale called dermal denticles or placoid scales, which are tooth-like structures that cover their skin.

Do sharks make noise?

Sharks are generally silent, but some species can produce sounds by grinding their teeth or through body movement.

How many rows of teeth do sharks have?

Sharks typically have multiple rows of teeth, with the number of rows varying by species. Some sharks can have as many as 15 rows of teeth in each jaw.

What do sharks taste like?

Shark meat has a firm texture and a mild, slightly sweet flavour, often compared to swordfish or tuna.

What do tiger sharks eat?

Tiger sharks have a diverse diet, including fish, sea turtles, marine mammals, seabirds, and even inedible objects like trash.

Are bull sharks dangerous?

Bull sharks are considered one of the more aggressive shark species and have been involved in several attacks on humans.

Are sharks cold-blooded?

Sharks are considered cold-blooded or ectothermic, but some species, like the great white shark, can maintain a slightly higher body temperature than the surrounding water.

Are there sharks in the Great Lakes?

There are no sharks in the Great Lakes, as they are freshwater systems.

Can dolphins kill sharks?

Dolphins have been known to defend themselves and their pod members from shark attacks, using their speed and agility to ram sharks and potentially injure or kill them.

How big is a megalodon shark?

The extinct megalodon shark is estimated to have reached lengths of up to 60 feet (18 meters) and weighed 100 tons (90,718 kg).

What is the most aggressive shark?

The bull shark is often considered the most aggressive species due to its territorial nature and tendency to swim in shallow, coastal waters where humans may be present.

Are lemon sharks dangerous?

Lemon sharks are generally not dangerous to humans, as they are not aggressive and feed primarily on smaller fish and invertebrates. However, as with wild animals, caution should be exercised around them.

Are nurse sharks dangerous?

Nurse sharks are generally docile and not considered dangerous to humans, but they can bite if provoked or feel threatened.

Can sharks swim backwards?

Sharks cannot swim backwards because of their rigid pectoral fins and how their bodies are designed for forward propulsion. However, some species can use their fins to help them move slowly in reverse.

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