Sharks Essay, Research Paper

SHARKS

Sharks are one of the most feared carnivores in the sea. There are 365 species of of sharks in the sea as we know today. All sharks are carnivores. Most of them eat live fish, including other sharks. A shark’s most common natural enemy is an another shark. Most sharks eat their prey whole, or they tear off large chunks of the bodies. Some sharks crush their prey. Others take out small pieces off flesh from large fish. Sharks also feed on dead or dying animals. Sharks have the reputation of attacking human beings. But less than 100 shark attacks a year are reported throughout the world. Sharks are most common in warm seas and oceans. Whale sharks, are the largest shark known to man. Sharks are classified in the order Selachii, which belongs to a larger class of fish called Elasmobranchi. The earliest shark-like vertebrate fossils are from the Devonian Period of the Paleozoic Era.

Some kinds of sharks live in the depths of the ocean. The smallest streamlined, black and white shark of the genus Squaliolus can grow to be up to 6 inches long and the female can grow to be up to 8 inches. They can grow up to 40 feet long. They are also known to weigh over 15 tons. The smallest sharks known at a full stage of growth may measure about 6 inches long and weigh about 1 ounce.

Sharks live in many places throughout the ocean. Some sharks are known to be found near the surface of the water because the temperature of the water is warmer. Yet, some sharks are known to dwell on the bottom of the ocean. These sharks are sometimes referred to as bottom dwellers. A few species of sharks enter rivers and lakes where they can move to the seas and oceans easily.

Sharks have a boneless skeleton made of a substance called cartilage. Most species of sharks have a rounded body, shaped somewhat like a torpedo. This type of flexible body makes their swimming in oceans and strong currents much easier. Their bodies are also shaped somewhat like a torpedo to give them a more streamlined affect in the in water. Yet, some types of sharks, the ocean dwellers have a flat body similar to that of skates and rays. Sharks can travel with great bursts of speed especially when attacking their prey or when excited. The fastest-swimming sharks have a moon-shaped tail that provides extra power and durability for swimming.

Sharks don’t have a swim bladder. This is what helps regulate depth control. Sharks do not have this organ. Yet, they do have a oil organ that also acts as a gas bladder. This oil is less dense than water and acts as a gas bladder.

A shark has multiple rows of teeth. The mouth of sharks is in the front of the head. In some species, sharks teeth are replaced as much as once a week. Some sharks have teeth used to crush and grind. These are some what like what humans have. They also have sharp teeth. These can be compared to incisors that humans have. These types of teeth are very important to sharks because they are carnivores and depend on their teeth in order to eat their prey. A sharks body in covered by scales which cover their bodies. These scales make the skin of a shark very rough and strong.

Sharks have a very different breathing system than most animals that live in or on this earth. Sharks also receive oxygen from the water through gills, yet, unlike fish, sharks do not have a gill cover. This makes a sharks breathing system very unique. Instead of a gill cover, sharks have from five to seven slits in the skin on each side of the head. Water passes through of these slits after the shark’s gills remove the oxygen. Most sharks cannot pump water over their gills, as do the majority of fish.

Sharks have special senses that allow them to compete for prey. They have excellent hearing, yet, can not hear many low pitched sounds. Sharks can find their prey the sounds that they make. Some scientists believe that the shark’s lateral line through out their back bone detects the lowest-pitched sounds. Sharks have sensitive eyes that can see extremely well in dim light such as most cats. Sharks also are believed to have small amount of color vision. Yet, sharks may not be able to see many details clearly.

Fertilization is internal in all sharks, and the males have slight changes of the pelvic fins known as claspers. They act as internal organs which are located in humans. Many species give birth to 60 or more pups in a litter, but most have far fewer. Each egg is enclosed a leathery capsule which at first is fully closed but soon allows a little sea flow in to the embryo. The parents do not take care of the young and in some cases may even eat them.

Shark eggs, unlike those of most fish, are fertilized inside the female’s body. The male shark has two organs called claspers, which release sperm into the female, where it fertilizes the eggs. Among most species of sharks, the eggs hatch inside the female, and the pups are born alive. At least 40 species lay their eggs outside their bodies.

Sharks belong to a group of fish known as Elasmobranchs. Rays and skates also belong to this group. The scientists frequently identify new species of sharks. But sometimes they find that two sharks that had been considered different species are actually the same.

-Thresher sharks are long-tailed fish that swim along the surface. They grow to a length of about 20 feet. The Thresher uses its long tail to gather into. Thresher sharks are called named that because of the way that they kill their prey. Which is scaring them then easily taking advantage of them.

-Basking sharks are the largest species of sharks known to man. They are measured to be 30 feet long and live in all types of water. This type of shark is known as omnivores because they only eat small animal and plant life called plankton. These sharks usually swim on the surface of the ocean.

-Hammerhead sharks, are a strange and odd type of shark, yet, are one of the strangest-looking sharks known to man. They have a flat head, which somewhat resembles hammer. They hammer head shark usually ranges from 20 feet to 22 feet long. Hammerheads live in shallow water and warm types of water.

-Bull sharks are another large type of sharks which can live in fresh water. They often enter rivers that empty into the sea. Bull sharks are known to attack many people on and offshore. If the movie “Jaws” were real; he would probably be a Bull Shark.

-Great White sharks are easily one of the most dangerous sharks known to man. They measure up to 21 feet long and live in cold water. Great White sharks are powerful and take advantage of such animals as seals and lions as well as other large fish.

-Mako sharks are one of the most powerful sharks known to man. A mako fights by leaping into the air. Most makos live in tropical and warm water. They may reach a length of 12 feet at full growth. Makos eat many small fish such as bluefish, herring, mackerel, and swordfish. There are carnivores. Makos have a reputation for attacking many small boat and being very aggressive.

Strange Facts

1. Sharks live all over the world, from warm, tropical lagoons to polar seas. Some even inhabit freshwater lakes and rivers.

2. Sharks are fishes. Like other fishes, sharks are cold-blooded, have fins, live in the water, and breathe with gills. A shark’s skeleton is made of cartilage.

3. A shark’s body shape reduces drag and requires minimum energy to swim.

4. Sharks eat far less than most people imagine. Cold-blooded animals have a much lower metabolism than warm-blooded animals. A shark eats about 1% to 10% of its total body weight each week. Studies on sharks in the wild show similar food intake.

5. Only 32 shark species have ever been known to attack people. Like other wild animals, most sharks would rather avoid you. Sharks that have attacked, probably mistook people for food or may have attacked to protect their territory.

Bibliography

Refrences

All About Sharks 3-15

Http://www.aj.com/main/metaanswer.asp?metaEngine=directhit&origin

Encyclopedia Americana- School’s Version 3-30

SHARKS!- 2-18 A Web Site with many new facts and information.

Http://www.sharks.com/info

McMillian’s Animal Kingdom 3-26

P.145-149

Discover Channel Online

www.discoveryonline.com/sharkcam