Agnatha Nervous System Research Paper

Sharks are aquatic creatures and very important to the living with lots of information humans may not understand. To start off, femeles give birth to 7-9 sharks per litter that are 3-4 feet at birth. Next humans believe all sharks are monsters but out of 400 species only 4 sharks have been claimed to attack on humans. Lastly sharks attack for 2 main reasons one reason is for defense and predation. They attack in defense when humans are in or around their territory they attack in predation mistaking people for seals. In conclusion sharks are creatures that humans are still learning about and try to understand them better.

Sharks have been in our oceans for almost 450 million years. Those millions of years of evolution have allowed many different shark species to develop abilities, and to become perfect predators.

Sharks grow slowly and reproduce at a low rate. Their natural rate of replenishment is low, because they reproduce late in life and produce few offspring (Sims and Reid, 2002). If too many of a certain shark species is killed in a certain area, it is possible that that species may never recover. For example, the number of dusky sharks and sandbar sharks off the eastern United States decreased by more than 80% between 1985 and 1995. The sand tiger shark and the great white shark are threatened world-wide. Despite reproduction, little is known about the status, behavior patterns, and their migration patterns of most

Shark mating rituals vary from the size of the shark and its specie. In smaller, more flexible species, the male coils around the female, while the male of the larger specie orients himself parallel and head-to-head with the female (Woums & Demski 1993). Some species mating rituals also consists of males biting females on the pectoral fins or the middle of the back to hold on to them (Woums & Demski 1993). The female will often bear scars or marks, after the ordeal. Due to the fact that sharks are cold blooded animals, there is no precise gestation time. The development of the embryo will depend solely on the temperature of the water, however, the gestation period can last anywhere from 2 months to 2 years (Woums & Demski 1993). Within shark species there are two methods of reproduction. In some cases a female shark will lay eggs in a coastal nursery where the presence of other sharks are absent. And in other cases, usually in the larger sharks, females give birth to live offspring (Wourms & Demski 1993). In which case the young are born fully developed, and once they are born they shoot away fast or they risk being eaten.

They also prey on smaller fish such as skates, eels, herring, and cod. On occasion remains of larger mammals such as seals, moose, polar bears, and reindeer have been found in their stomachs. Its even speculated that these sharks ambush seals, with their ice holes being like beacons. Female Greenland sharks are ovoviviparous, meaning that they retain the developing embryo inside of their bodies to hatch instead of depositing it into the mud. While the gestation period is unknown there are usually 10 pups per litter that are about 90 centimeters

Humans are just like sharks. Humans eat meat they have live babies and sharks make mistakes just like humans. Sharks are very interesting creatures but people don’t give them a chance because people make them sound like they are terrible beasts. Many people are more likely to get killed by a car crash then by a shark. If people keep killing sharks for fins there will be no more sharks.

This article talks about what sharks does in order to survive and what are they capable of doing. According to the article, sharks do not sleep; but rather, they have rest periods throughout their day. Sharks are capable of hearing anything below 1000 Hertz and can also swim up to 20 mph. Sharks skeleton is made up of cartilage rather than bone. According to the article, cartilages are lighter than bones. What keep them from floating are their large livers. Sharks can gather and keep the air into their stomach to keep them from floating.

The author of Your Inner Fish, Neil Shubin, discovered a “missing link”, a fossil he called Tiktaalik. Tiktaalik shows features that connect the evolutionary gap between fishes and land-living animals. Shubin demonstrates in the first four chapters how different branches of science prove that many organs within numerous creatures, ancient or living, are deeply related. For the following chapters he discusses the resemblances between the designs of bodies, skulls, hands, eyes and ears belonging to most of the beings of the animal kingdom.

In the article, “How a Seahorse Dad is like a Pregnant Woman” by Sarah Zielinski, may sound comical, but much to my surprise, has some biological information that is worth reading. Unlike human, beings male seahorses carry the babies, instead of the women. A male seahorse carries the eggs of his mate in a pouch. Inside the male is where the eggs become fertile and start the growing process. The pouch, or the homes of the eggs are inside the male, around the stomach region. The male’s pouch is very adaptable. When the male is not pregnant the pouch is not sealed off, but when there are eggs in the pouch it becomes sealed, isolated from anything else. When eggs occupy the pouch it adapts its size and the nutrients it realizes according to the

Shark attacks are rare, and most are not even fatal. In fact, there are only 70 to 100 shark attacks on average around the world. You are more likely to die from fireworks, drowning, a car accident, or a heart attack than you are a shark bite. Better medical care and faster response times means that if you are bit by a shark there is a high chance that you will survive. Most sharks take one bite as a test, to find out if you are edible or not. If you are not, the shark simply swims away to find a tasty seal or fish to eat instead. (FLMNH Ichthyology Department, 2005).

Bull sharks swim upstream into lakes and other fresh water bodies to have offspring this is an advantage for them because no other shark can live in fresh water and not many predatory fish live in fresh water so their young can live there until they are big enough the defend themselves against other predators. The Bull shark can survive in both salt and fresh water because they take in salt water and hold it in a gland so that when they go into fresh water they have enough salinity to stabilize them until they head back into salt

The following section was entitled “What Does Developement Tell Us,” and in it, Jeffery described the developmental phases of Astyanax because “evolutionary changes proceed through alterations in development.” By describing the different phases, Jeffery was able to point out the places where the development of the eyes in cavefish morphologies is different from the surface-dwelling fish. The first phase of eye development in both forms of the Astyanax is the appearance of optic vesicles, and with this appearance and other simultaneous mechanisms, the eye primordia, consisting of the lens vesicle, an optic cup with an inner retinal layer and an outer retinal pigment epithelium layer, and optic stalk, forms. I found it extremely important

Do you ever wonder what the scariest animal is? There are many different animals, but the most feared is the shark. They are the most unique creatures in the ocean. They have hundreds of teeth in their mouth which make them seem scary. When sharks lose their teeth, there is always another tooth to replace it. Sharks have been around for more than 75,000,000 years. They are located all over the world. There are more than 300 species of sharks. These creatures have many talents and are very intelligent. I am not afraid of sharks because they are helpful to the environment, they can spit garbage out, and sharks are protective of their homes just like we are.

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

The organs of our body are controlled by many systems in order to function correctly and efficiently in order to survive within the environment we live in. These include the heart, stomach and intestines and other vital organs and body systems. All of the systems in our body are regulated by a part of the nervous system called the autonomic nervous system (ANS). The ANS is part of the peripheral nervous system and it controls many organs and muscles within the body. Rather bizarrely we are unable to determine or feel its presence in our bodies as it is working involuntary, as a reflexive manner. A common example of this involuntary action is best understood when