FREE ESSAY ON DIFFERENT TYPES OF SHARKS

DIFFERENT TYPES OF SHARKS

Different Types of Sharks 
INTRODUCTION Although sharks belong to the class Chondrichtyes, there are many different
types. Sharks arose about 350 million years ago and have remained virtually unchanged for
the past 70 million years and still comprise a dominant group. It is thought that sharks
almost certainly evolved from placoderms, a group of primitive jawed fishes. It took a
long series of successful and unsuccessful mutations with fin, jaw positions etc to give
us all the different designs of sharks around today. When asked to draw a shark, most
people would draw a shape along the lines of the whaler shark family, tigers or a
mackeral shark such as a porbeagle. However many people do not realize the sheer
diversity in the shape of sharks, or that rays are really sharks. Seldom does such an
animal inspire such a variety of emotions reflecting a mixture of fascination, awe and
fear. Sharks have occasionally exacted a terrible price from humans who have trespassed
on their territory. No better understood than the ocean that they inhabit, these
creatures should be regarded in the same way as lions, tigers, and bears: as dangerous,
predatory but nonetheless magnificent animals. Different Types of Sharks Living sharks
are divided into eight major orders, each easily recognizable by certain external
characteristics. Each order contains one or more smaller groups, or families. In all
there are 30 families of sharks and they contain the 350 or more different kinds or
species of sharks. The eight major orders of sharks include the Squantiformes,
Pristiophormes, Squaliformes, Hexanchiformes, Carcharhiniformes, Lamniformes,
Orectolobiformes, and the Heterodotiformes. The orders have distinguishing
characteristics that fit in each. The Squantiformes normally have flat bodies that are
ray-like with mottled dorsal surfaces. These sharks have a short terminal mouth, which is
armed with small impaling teeth. They also have a caudal fin, which has a lower lobe that
is longer than the upper lobe. Their pectoral fins extend forward over the ventrally
directed gills. The Pristiophormes have more of an elongated snout, which is saw-like and
edged with slender, needle-sharp lateral teeth. They have two dorsal fins and no anal
fin. They use short transverse mouths and small cuspidate holding teeth in both jaws.
Squaliformes have no anal fin as well, but their snout is not elongated, but is somewhat
long. Many have powerful cutting teeth in both jaws. In some species these razor sharp
teeth are in the lower jaw only and the upper teeth serve to hold the food.
Hexanchiformes have six or seven gill slits. They are sharks with a single spineless
dorsal fin, and an anal fin. The typical Carcharhiniforme has an elongated snout, a long
mouth that reaches behind the eyes, an anal fin and two spineless dorsal fins. The eyes
have movable, nictitating lower eyelids worked by unique muscles. Teeth vary from small
and cuspidate or flattened to large and bladelike. Carcharhiniformes have no enlarged
rear crushing teeth. Along with this they have a spiral scroll intestinal valve. A
Lamniforme shark has an elongated snout. Most have long mouths that reach behind the
eyes, an anal fin and two spineless dorsal fins. They also have a ring intestinal valve.
The Orectolobiformes have pig-like snouts and short mouths that in most species are
connected to the nostrils by grooves. There is an anal fin but no fin spines on the two
dorsal fins. They have uniquely formed barbells at the inside edges of the nostrils.
Heterodotiformes are the only living shark that combines fin spines on their two dorsal
fins and anal fin. They only have five-gill slits. In each order there are specific types
of sharks. Each shark belongs to a family with different species. The Angel shark
(Squantiforme) is just one of the many. It has a single family of about thirteen species.
They are all ovoviviparous livebearers and most do not exceed 1.5 meters. Saw sharks
(Pristiophoriformes) are harmless bottom sharks. They are also a single family but with
five species. They are also ovoviviparous livebearers. Four sharks that belong to the
order Sqauliforme are the Bramble, Dogfish, and Rough sharks. They have three families
with eighty-two species. They too, are ovoviviparous livebearers. They have more
cylindrical bodies. Frilled sharks, Six, and Seven gill sharks (Hexanchiformes) have two
families and five species. Once again they are also ovoviviparous livebearers. Usually,
these guys are found in deep waters. The Catsharks, Finback Catshark, False Catshark,
Barbelled Houndshark, Weasel, Houndshark, Hammerhead, and Requiem sharks
(Carcharhiniformes) have one hundred and ninety-seven known species. Most of these sharks
are known to be dangerous. They are both oviparous and ovoviviparous livebearers. This is
not the type of shark you would like to have grace you presence. From the order of
Landformes is the Sand, Basking, Goblin, Crocodile, Megamouth, Thresher, and Mackerel
sharks. They come complete with seven families and fifteen or sixteen species. All of
them are ovoviviparous livebearers. These sharks are found in all seas except Arctic and
Antarctic. The last group of sharks would be the Collared Carpet sharks, Blind,
Wobbegongs, Zebra, Longtailed Carpet Sharks, Whale, and Nurse sharks. They all belong to
the order Orectolobiformes and have seven families and thirty-three species. These sharks
prefer the warmer water and are both ovoviviparous and oviparous livebearers. Obviously
these sharks come in many different sizes and some are more dangerous than others. At
least eighteen species in four families and nine genera have been implicated in attacks
on humans. Obviously a small shark such as the Pygmy is harmless, but they still must be
treated as a predator especially the bigger ones. The smallest of all sharks is the Pygmy
Ribbontail Catshark, which is about 0.24 meters. Next in line from smallest to largest
would be the Port Jackson Shark, which is about 1.65 meters. After them would be the
Ornate Wobbegong (2.88m) and then the Bull shark (3.4m). The average sizes go drastically
up from there to the Great White shark, which is incredibly larger, its about 6.4 meters.
The two greatest sizes are the Basking shark (7.8m) and the Whale shark (13.7m). These
sharks listed here are definitely not all the sharks in the world, they were just meant
to give an average range of size for all sharks. Some of the most dangerous sharks range
from about 2 to 8 meters. The Hammerhead, Great White, Tiger, Blue, and the Bull shark
name a few. There are many types of sharks lurking around in today's ocean. In every one
is unique in its own way. Some are different by size, shape, eating habits, or even the
way they breed. Although with all these differences they are all very similar and that is
why the shark is one of the most amazing creatures of our time. Summary Although sharks
belong to the class Chondrichtyes, there are many different types. Sharks are divided
into 8 major orders. Each order contains 1 or more smaller group. There are 350 or more
different kinds of species of sharks. The 8 orders are named the Squantiformes,
Pristiophormes, Squaliformes, Hexanchiformes, Carcharhiniformes, Lamniformes,
Orectolobiformes, and the Heterodotiformes. These orders group sharks according to
certain distinguishing characteristics. The Angel shark, Saw shark, Frilled shark,
Hammerhead shark, Sand shark, Wobbegongs, and more all belong to a specific order due to
their characteristics. Each one of these sharks come in different shapes and sizes. Some
are more dangerous than others. The more dangerous sharks range from about 2 to 8 meters.
It is obvious that sharks are one of the most amazing creatures of our time. 
Among some of the most wasteful reasons to hunt in the world I'd have to say that besides
the killing of elephants for their tusks, this is on top of the list for one of the worst
reasons a blue shark is killed. And sadly enough the United States is one of the top
countries to blame. In Hawaii and Mexico shark finning is very common. The fishermen fish
the sharks take the fins, and throw it back into the water. The fins are mainly used for
fin soup as a status symbol for the Japanese. They eat it for fin soup. Since the fins
contain a high dose of ammonia smell and taste they must be processed quickly and tossed
back into the ocean, and a lot of times the fish is thrown back into the water alive.
Conservation's main cause for concern is the fact that the sharks have a very low
reproduction rate. They don't typically reproduce until the age of twenty-five, and even
then they only produce a few babies. At The rate these fishermen hunt them the sharks
will possibly become endangered in the next few years. This is one of the most cruelest
things I've ever heard, and not just the killing of them for the fins, but that fact that
they are thrown back into the water without fins. How is the shark supposed to survive
and even swim? That is so cruel. Maybe someone should cut off fishermen's legs and arms,
and watch them try to survive. It probably would probably hard for the fisherman to
survive, he'd be a physical vegetable. I hope the United States does something urgently
to control this growing problem before it gets out of hand. The people can do something
about it by obviously not buying shark products but also by writing letters and sending
petitions to congress, we could also spread the word in other ways in Japan and Hong
Kong. But I think if the US stopped the finning, other countries would probably follow
and sales would go down, giving the sharks a chance to live and breed in peace.
Bibliography 
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pp. Clark, E. 1981. Sharks, magnificent and misunderstood. National Geographic
160:138-186 (Aug. 1991) Compagno, L. J. V. 1984. FAO species catalogue. Vol. 4. Sharks of
the world. An annotated and illustrated catalogue of shark species known to date. Part 2.
Carcharhiniformes FAO Fish. Synop. (125) Vol. 4, Pt. 2: 251-655. Conniff R. 1993. From
jaws to laws - now the big bad shark needs protection from us. Smithsonian 24: 32-43
(Number 2, May1993). Burgess, R. F. 1970. The sharks. Doubleday & Company, Inc., Garden
City NY. 159 pp