Essay on Shark

 Essay on Shark

Essay on Shark: Sharks are one of the ancient species on Earth. Scientists believe that sharks existed more than 400 million years ago - long before the dinosaurs.  More than 500 shark species are found on the earth. River sharks are found in some rivers in Australia, South Asia as well as New Guinea. In Japan and Australia, sharks are common seafood.

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Introduction

Sharks are one kind of fish, which fall into a subclass, called Elasmobranchii. Sharks are the top predators of the oceans. Scientists believe that sharks existed more than 400 million years ago - long before the dinosaurs. Until the 16th century, sailors called sharks "sea dogs”. More than 500 shark species are found on the earth. Different species of sharks have different sizes. The small dwarf lanternshark is only 17 cm in length, the smallest shark in the world. Whereas the world's largest shark is the whale shark, length is 40 feet to 55ft. The sharks who are at the top of the food chain or apex predators are the Great White Shark, Tiger Shark, Hammerhead Shark, Mako Shark, etc. 

Description and Behavior of the Shark

Sharks belong to a subclass Elasmobranchii. Their skeleton is not made of bones, but rather it is made of flexible and durable tissue called cartilage, which helps to reduce the weight of their skeleton. Sharks have no rib cages. Since there are over 500 species of sharks, they vary in size. Some species of sharks have spots or stripes on their skin such as Zebra sharks, Tiger sharks, which help them to camouflage. These markings also make it difficult for their prey to locate them.

The tail fins of a shark, also known as the caudal fins. The top half of their tail fins are much longer than the lower half and this type of shape helps them to slow cruising and sudden bursts of speed or twist and turn. Shark’s eight fins are: two pectoral fins, two pelvic fins, a first and second dorsal fin, a caudal fin, and an anal fin which help them with swimming, steering, stability, thrust, lift, and propulsion as well as communiction.

As all species of sharks are carnivorous, they have powerful jaws with sharp teeth. Different species of sharks eat different types of food so they have different types of teeth like needle-like teeth, dense flattened teeth, pointed lower with triangular upper, and non-functional teeth. Bull shark's jaws are in 7 series with 50 rows of teeth. Most sharks can have up to 300 teeth, but they lose at least one tooth every week, however, new teeth grow within a day. Some sharks lose 30,000 to 50,000 teeth in their lifetime.

Shark liver is large and is full of oil. Their liver and cartilage help them swim. The shark's 5 to 7 gill slits are lined up on either side of their head. Spiracles are modified slits that play a vital role in respiration. When the shark moves, water passes through the mouth and gills in a process called "ram ventilation." Essay on Water Pollution

Shark has a “J-shaped” stomach and a short-length intestine. They take a long time to digest their food. When unwanted items are unable to pass out of the stomach, the shark vomits to expel unwanted items from its mouth.

Sharks have excellent eyesight which is about 10 times better than humans but they are color blind. Sharks have a layer of mirrored crystals, called tapetum lucidum which lie behind the retinas. This layer or tapetum lucidum helps them to see in turbid water and in very low light. Some species of sharks have a transparent or translucent third eyelid called the nictitating membrane, which helps them to protect their eyes as well as moisten them.

Sharks have an excellent olfactory system and sense of smell which is absolutely necessary for their survival. They also have a very good sense of hearing and are able to hear prey from many miles away.

Sharks have a swimming speed of about 8 km per hour, but their speed can reach over 19 km/h when attacking or feeding. 

Different shark species have different lifespans. The Greenland shark can live 250 to 500 years whereas the Blue sharks live only 15 to 16 years.

Diet of Shark

As sharks are carnivorous, they consume large to small fish, marine mammals, squid, crustaceans,  shrimp, seals, turtles, octopus, dolphins, sea lions as well as plankton, etc. Sharks attack in packs when they hunt large prey such as dolphins. 

Only four species of sharks such as Bull sharks, Great white sharks, Oceanic whitetip sharks, and Tiger sharks are dangerous to humans.

Habitat of Shark

Sharks live in seas and oceans but some species like the Bull shark and the River shark can live in seawater as well as freshwater. Sharks live at a depth of 7000 feet of seawater but some species may survive deeper. Sharks are found in the coral reefs where they get plenty of food such as crab, lobster, fish, etc. They are also found in sandy plains, estuaries, as well as shallow coastal water.

Some species of sharks like Horn Shark, Catshark, etc can live in aquariums for a period of one year or more. 

Conclusion

Sharks are killed by the people for their meat and fins. In Japan and Australia, sharks are common seafood. In South India, baby sharks are cooked which is called “sora puttu”. Sharks are captured for their fins which are used for making “fin soup”. 

Habitat loss, coastal development, pollution, shark culling, and many more are threats to sharks.

The International Union for Conservation of Nature has listed 25 species of sharks as critically endangered.

Governments of some countries introduced some laws to protect the sharks. In 1991, South Africa first declared the Great White Shark a legally protected species.

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Essay on Shark 250 Words

Shark is a fish, lives in open oceans as well as freshwater. The earliest types of sharks are 450 million years ago, towards the end of the Ordovician era. Their body is not made of bones but of cartilage.

Sharks have 5 pairs of gill slits behind their head which help them to filter oxygen from the water. More than 500 shark species are found on the earth. Sharks have numerous sharp teeth in their powerful jaws. They have a tooth replacement system through which sharks quickly replace shed teeth.

Sharks prefer to eat fish, crab, plankton, turtle, dolphin, and other sea creatures. 

Sharks are found in every sea or ocean but some species are kept in aquariums as captive such as zebra sharks, leopard sharks, etc.

Sharks have excellent eyesight and hearing which helps them to catch their prey. 

 Sharks are apex predators or top predators so they play a crucial role in maintaining the ecosystem.

 The world’s largest Whale shark is about 60 feet in length and lives in Australia, South Africa, the Galapagos Islands, Belize, etc. The world's smallest shark, the Dwarf Lantern, is only 6 to 7 inches long and lives in the Caribbean Sea, the Hawaiian Islands, eastern Mexico, western Florida, etc.

Currently, about 75 percent of shark species are threatened by poaching, capture, and hunting for their fins, skin, and meat. We need to put an end to such things and encourage others to do the same for this reason “Shark Awareness Day” is celebrated every year on 14th July.

10 Lines on Shark

1. Sharks are one of the ancient species on Earth.

2. Sharks were hovering over the oceans about 420 million years ago.

3. Sharks have small pores called the ampullae of Lorenzini, located near their nostrils and beneath their snout, which help them to catch their prey by detecting the electrical fields.

4. hammerhead sharks have impressive binocular vision and can see 360 degrees.

5. River sharks are found in some rivers in Australia, South Asia as well as New Guinea.

6. The biting power of a great white shark is four times more powerful than that of a lion or a tiger.

7. Blue Sharks give birth to 135 to 138 puppies in a single litter.

8. Sharks have a huge olfactory bulb that connects to their nostrils which helps them locate prey.

9.  Sharks have the ability to hear their prey up to 3,000 feet away.

10. About 37% of the world's sharks and rays are considered threatened by 2021.