Sharks 101 | National Geographic

Summary

Sharks, ancient and awe-inspiring, dominate the oceans with their incredible speed, grace, and strength. From the giant whale shark to the prehistoric megalodon, these creatures have evolved remarkable traits, like endless teeth replacement and specialized hydrodynamic skin. While some sharks give birth to live young, others lay eggs, with some species exhibiting brutal competition in the womb. Sadly, overfishing, particularly for the shark fin trade, threatens their survival, with populations declining drastically. Efforts are underway to protect these apex predators, aiming to ensure their continued existence and the health of marine ecosystems.

Takeaways

• 😀 The whale shark is the largest living fish, growing up to 40 feet long and weighing 15 tons, with a mouth spanning 4 feet wide.
• 😀 The megalodon, an ancient predator that lived over 20 million years ago, could grow up to 80 feet and weigh around 70 tons, making it the largest fish to ever exist.
• 😀 Sharks continuously shed and replace their teeth throughout their lives, with some species shedding up to 30,000 teeth.
• 😀 Most sharks have multiple rows of teeth, with the great white shark containing up to seven rows and 300 teeth at once.
• 😀 The cookiecutter shark loses all of its lower jaw teeth at once, unlike other sharks that lose them individually.
• 😀 Mako sharks are the fastest known sharks, reaching speeds of up to 46 miles per hour due to their hydrodynamic body design.
• 😀 Shark skin is covered in dermal denticles—flat, v-shaped scales that reduce friction and help sharks move efficiently through water.
• 😀 Sharks have skeletons made of cartilage, making them lighter and more agile in the water compared to animals with bone skeletons.
• 😀 Sharks reproduce in unique ways: some lay eggs, while others give birth to live young. The sand tiger shark pups engage in sibling competition before birth.
• 😀 The shark fin trade is responsible for the deaths of approximately 100 million sharks annually, contributing to the decline of shark populations by up to 70%.

Q & A

What is the largest living fish in the world?

The largest living fish is the whale shark, which typically grows to about 40 feet long and weighs around 15 tons.

How does the size of a whale shark compare to that of the megalodon?

While whale sharks are massive, they pale in comparison to the megalodon, which could reach lengths of up to 80 feet and weigh around 70 tons, making it the largest fish to have ever existed.

What makes the megalodon different from modern whale sharks?

Unlike whale sharks, which are filter feeders, the megalodon was a carnivorous predator that consumed anything that fit into its nearly 10-foot-wide mouth.

How many teeth can sharks shed throughout their lives?

Sharks can shed over 30,000 teeth throughout their lives, unlike humans who have a set number of teeth.

What unique feature do sharks have in their teeth compared to humans?

Sharks have multiple rows of teeth in their jaws, with some species having up to seven rows that can hold as many as 300 teeth at any one time.

Which shark species is known for replacing its teeth in a unique manner?

The cookiecutter shark is known for losing and replacing all its teeth in its lower jaw at once, unlike other sharks that lose teeth individually.

What is the fastest shark and how fast can it swim?

The fastest known shark is the mako shark, capable of reaching speeds of up to 46 miles per hour.

How does the design of a shark's body contribute to its speed?

Sharks have a torpedo-shaped body and flat, v-shaped scales called dermal denticles that reduce friction and help them swim quickly and quietly through the water.

Do sharks have skeletons made of bone?

No, sharks have skeletons made of cartilage, which is much lighter than bone, reducing their overall body weight.

What are the differences between egg-laying and live-bearing sharks?

Egg-laying sharks produce a few large eggs that develop in external wombs, while most sharks give birth to live young, with gestation periods of around one year.