Essay/Term paper: Sharks

Essay, term paper, research paper:  Science

Sharks


"It"s tail swayed slowly from side to side, pushing the hunters body
through the murky water. All signs of motion were non-existant, except for the
rhythmic movement of the water over the five gill slits on either side of it"s
head. Slowly gaining speed, the shady figures unmoving eyes fixed on it"s
target, a lost harbor seal pup. As the distance between the predator and it"s
prey grew closer, the jaws of the massive fish drew forward, exposing nearly
eight rows of razor sharp teeth. Strings of it"s previous meal hung in rows
from between it"s teeth. Sensing danger, the harbor seal frantically tried to
find a place to seek refuge, but it was too late. The jaws of the shark closed
around the seal with an astounding 14,000 pounds of pressure, cutting the seal
in half. The Great White shark claims another victim.1"
Any one who"s seen the famous movie series "Jaws" may look at the Great
White Shark in a similar manner. Perhaps it"s the way that Hollywood uses a mix
of fact and fiction in the series. This may have frightened many people into
hating the Great White for it"s ferocity. It might have also been the size of
the shark in the movie that"s kept thousands of people off the beaches and out
of the water. Better yet, it could have been the overall storyline: A Great
White shark with an eating disorder and a taste for human flesh. Perhaps that"s
what is keeping vacationers from grabbing their trousers and snorkels.
Over all, there have been 1026 attacks on humans by sharks in the last
ten years. Only 294 of these attacks have been linked to Great White sharks.
That"s roughly the number of people who drown each year in swimming accidents.
Of these 294 attacks, less than eighteen percent were fatal. Out of the
eighteen fatal incidents more than seventy percent was contributed to loss of
blood. This means that the shark didn"t kill the victim. The shark bit the
victim and then released them (also known as the taste test). The shark samples
the victim by nibbling on an appendage or two often resulting in a severed
artery or other major blood vessel. Therefore, the Great White should be
considered a mantaster not a maneater.
This intrigued scientists considering the size of the sharks brain. The
Great Whites brain is about one half the size of a dogs. Over seventy percent
of the brain is used for tracking prey. The other thirty percent is used for
body functions. Studies show that the sharks main purpose is to eat. People
think that the sharks main purpose is to kill. This is incorrect, sharks only
eat when they are hungry. Impulses from the brain are sent to the jaws and the
stomach telling the shark that it is time to hunt for food.
"Why do sharks not follow a basic attack pattern on a human? In a human
attack, the primary strike is usually the only contact, as though the shark
finds us(humans) to be unpalatable. There is a theory on this as well,
involving the differences in our anatomy and the pinnipeds(seals, sea lions).
We are mostly muscle where the pinniped body has a great deal of fat. It is
theorized that the shark somehow senses this and abandons us as a potential meal
because our bodies are not as energy-rich as the pinnipeds. Of course, this is
often enough to kill us - or at least, really screw up our day!"

Cold Hard Facts

The Great White shark has remained unchanged for 250 million years. It"
s greek name is Carcharodon carcharias. This is derived from carcharos meaning "
ragged" and odon meaning "tooth". There isn"t a defined size range for the
Great White but most experts agree that the length of the shark is usually
between 12 and 16 feet with the maximum figure being about19 to 21 feet. (The 21
foot is an actual record from 1948. The largest ever recorded!) If the Great
White is that big try to imagine the size of those massive jaws and teeth, Not
to mention the enoromous power behind those jaws.. These huge eating machines
used to be even bigger! The Great White was once known as Carcharodon megalodon.
The only difference in between the Great White and this previous model is size.
The Carcharodon megalodon was MASSIVE compared to the modern day Great White.
Averaging forty to forty-five feet in length, it is theorized that this giant of
the deep could swallow a city bus whole. There are many scientists who theorize
that there may still be some of these giants down there... down deep enough
where the bodies would never wash up on shore.
The Great Whites teeth are serrated like a bread knife. Averaging about
one to two inches in length and about one-half to one inch in width. These
teeth are so ragged and so sharp, old native spears have been found with these
teeth on the end of them. Scientists think the natives used these spears as
saws!
The most mysterious aspect about the Great White is it"s life span. No
one in history has recorded the life span of one individual shark. There was
one shark though, that was tagged and observed returning every two weeks or so
to feed. This observation went on for some eighteen years!! Is this shark
young? Is it old? No one can say for sure.
Of all the animals with a good sense of smell, the Great White tops
them all. One Great White can sniff out one drop of blood more than a mile
away. This is after the drop of blood has been diluted by billions of gallons
of water. All of this is possible because of fluid filled sacs on both sides of
the fish called lamellae. These sacs run the length of the fish. The walls of
the tubing is so sensitive, vibrations as far away as eight miles can be felt.
Many people think that if they don"t have any cuts, lacerations, or abrasions,
they"ll be safe in the water. WRONG. The sharks nose has twenty to thirty
little black "freckles". These freckles can not only pick up the scent of blood,
it can also detect electrical fields as tiny as .005 microvolt. That"s the same
as some one feeling the electrical jolt of a D-sized battery through a 1,000
mile long copper wire(that"s not very big). Every living thing and most non-
living things put out a small electrical field when in the water. The main
reason sharks attack the bleeding victim first is because the blood in the water
releases more ions, thus magnifying the electrical field as well as the scent.
The Great White can swim at incredible speeds, sometimes as fast as
thirty-five knots(roughly 25 miles per hour). No human alive could stand a
chance at out swimming a Great White shark. The fastest human swimming record
is held at a little over two miles per hour.
Great Whites have enormous appetites. In one meal, a Great White can
eat almost eight hundred pounds of seal meat. Because of the amount of meat the
shark consumes in this meal they can go without eating anything else for nearly
a month. The Great White"s diet consists of mainly lingcod, salmon, tuna, squid,
other sharks, cetaceans (dolphins and whales), and pinnipeds. They also show a
preference for carcasses, especially large whales. With some research done off
the South Farallon Islands, located off the coast off San Francisco, states that
most of the shark attacks take place at the same time. This is supported by the
fact that Great Whites eyes are really sensitive to daylight viewing. The time
of day for the attacks is the same because the seals are forced each day to go
into the water because of the tides.

"The attack stratergies of the Great White were different on each
species of the prey. The Seal is usually attacked on the surface of the water,
by the shark rising from below. A large flowing blood stain at the surface
indicates that the Great White carries the seal underwater before removing a
bite then releasing the carcass, that floats to the surface.The shark almost
always aims for the head, since the seal has alot of blood vessels in that
area.3"

The seals death is brought on by loss of blood or decapitation. The Sea Lion a
diferent type of attack method is used. The first attack is usually the most
brutal. The shark attacks while the sea lion is on the surface, the strike
propels the shark out of the water while the sea lion is still held in the
beasts powerful jaws. It is then released to float to the surface to bleed to
death, then the shark returns later to feed on the carcass.
Great Whites are considered fish, but that doesn"t make them entirely
like other fish. To start off, their skeleton is made completely of cartilage.
This is the reason that no shark bones have been found. Cartilage is a soft,
flexible material that is light weight and floats in water(You can find it in
your nose if you move it from side to side). The cartilage plays an important
role in a sharks survival and buoyancy. Sharks have no gill muscles so they
must continue to swim in order to breathe. They even swim when they are asleep!
One exception is the Nurse shark. This shark has gill muscles and spends most
of it"s time on the bottom of the ocean waiting for food to scuttle by. When a
fish must swim to survive, it"s skeleton should be lightweight so the water
pressure doesn"t push the fish down towards the bottom. Sharks also hunt. The
cartilage helps relieve the stress of the water resistance as the shark swims.
The sharks skeleton is hollow on the inside. Each bone is filled with a mixture
of air and fluid. The shark can regulate the amount of air in these bones by
secreting a fluid that makes the body of the fish heavier. In turn, the shark
slowly descends into the depths of the ocean. When the shark wants to come back
up, it drains the fluid into its urinary bladder. The gills filter the air from
the water and fill the bones with air once again. The shark becomes lighter and
can come up to the surface.
Any one with enough courage to actually get close enough to touch the
skin surface of a shark, they"ll notice that it"s very smooth if you rub it one
way, but if you rub it the wrong way, watch out! Thousands upon thousands of
sharp "spikes" cover the shark. These spikes are called denticles; sandpaper
rough along the side, but razor sharp on the tip. Scientists believe that the
denticles are used to cut the victim if it"s eyesight is failing or it"s dark.
Once the shark cuts the victim, the blood gives off a more accurate position on
the prey. The shark can then home in on the wounded animal and make it"s
initial strike.
Sharks are considered fish, but what differentiates sharks from the
ordinary guppie? One is shape. The normal fish is not as broad shaped in the
frontal area. Sharks have broad heads and oversized mouths evolved for eating.
Their tail fins are not identical in shape to each other. The upper fin is
bigger in size and shape than the lower fin. Another difference lies inside the
jaws. The fish has teeth used for grasping prey. The shark however has larger,
more broad teeth used for shredding and tearing meat. The third difference is,
of course, in the skeletal system. Sharks have the cartiliginous skeleton while
the everyday guppie has bones. Why? The answer lies in the size difference
between the two animals. In the ordinary fish, there is less surface area.
Less force is needed to move the fish in a forward direction. Because of the
sharks broad frontal area and immense size, a much greater force is needed to
move the shark. Having the light skeletal system reduces the weight
tremendously and less force is exerted. A less obvious difference is the extra
set of fins on the shark. The pelvic fins are located just below the dorsal fin
on either side of the shark. The fish does not have the extra set of fins. It
is determined that the extra fins are used to stabilize the shark during
migratory swimming and hunting.