Matthew Alvarez

May 19, 2013

1st period

Comparative Anatomy

In the animals that we dissect have very similar organs that are somewhat similar but are sometimes used for different purposes. The animals that we dissect are a frog, crayfish, earthworm, and a rat. In this essay, try to differentiate the differences between them.

Frog



Skeletal System: The frog bone structure is almost like most bone structure but has it's difference. In the skeleton of the frog that I saw, it had no ribs. This could be a evolutionary adaptation because it might have not needed it for certain purpose. The frog has a endoskeleton which means that it is on the inside. This is helpful for the frog because it has mucous which is like mucus. It has a hollow flat skull, so this is an advantage because it can help it see better than others like us. The frog has no fibula, but it does have a tibiofibula which can help it jump farther unlike us human beings. It gets more push off with this bone. 

Muscular System:The frog has ligaments and muscles that are attached to the bone which gives it a more range of motion. Their lags and abdomen are the strongest muscle in their body because those are the muscles that the frog uses the most. It uses the muscles in it's leg for when it jumps in the air.The muscle in it's abdomen are used when it lands and doesn't land back on it's leg but on it's stomach.
Digestive System:The frog is more of a carnivorous diet which means that it has both plants and animals. The frog has a bigger than average liver because of all the bad things that it digest. The frog has a duodenum which is the first part of the small intestine which is where most of the breakdown of food is at because of the enzymes it has in it. The ileum is the last part of the small intestine which absorbs vitamin B and bile salt. The cloaca is the opening to all of the organs inside of the body which help get rid of waste that is unwanted in the body. The frog's digestive system is more complex than it is simple because of the way it goes through the body and how it is broken down and turned into nutrients. This is better for the frog because it lets it get more nutrient than if it had a simpler digestive system.
Respiratory System: The respiratory system of the frog is somewhat similar to us humans but it also has its differences. There are three main components in the frog's respiratory system: the skin, mouth, and lungs. The skin is used for cutaneous respiration which just means that air can get through the skin. The mouth is used for buccal respiration which is more commonly known as the part when the expands its chest. The lungs are used for pulmonary respiration which is exactly what our lungs do.
Circulatory System: The circulatory system is different in many ways compared to our system. In our body, we have a four-chamber heart but a frog has a three-chamber heart. The reason why they have one less chamber than us is because they can get some oxygen through their skin which is something that we can't do. They have a closed circulatory system because they have blood vessels. The vessels are similar to us because the blood is delivered to muscles and other body parts.

Earthworm

Skeletal System:The earthworm is quite different from the frog. instead of having a endoskeleton like the frog, it has a skeletal system called a hydrostatic skeletal system. A hydrostatic skeleton is parts of the body where it is filled with fluid with muscle around it, and the pressure of the fluid moving from one place to another help it move. This can also help support it body because o the pressure that it has. 
Muscular System:The muscular system of the earthworm is very different from the other three animals. It has two main and key muscle, which are the circular and longitudinal muscles. The circular muscle goes around the perimeter of the earthworm and the longitudinal goes up and down the earthworm. These muscle are the ones that push the fluid around the body in order for it to move. it also has bristle; which scientifically are called satae, are on the bottom of the worm which also helps it move forward. It has very few muscles in it's body which makes it much less complicated than the other animals. 
Digestive System:In a earthworm has a crop which is like a stomach to the earthworm. It is the part that stores food before it gets to the rest of the digestive system. The gizzard is a part of the earthworm that chews up it's food. This is a substitution to teeth since it doesn't have any teeth. The typholosole is a part of the intestine that make the surface area of the intestine bigger to digest more soil than average.This is advantage because it doesn't need as much energy as much as we need. Some disadvantages are that if one of the organs fails, the whole system shuts down.
Respiratory System: The respiratory system is very simple compared to our respiratory system. The only way the earthworm gets the oxygen that it needs is through it's skin. The way that it does it that the oxygen goes in through the skin by diffusion. Then, the carbon dioxide is passed through the skin into the air by diffusion. 
Circulatory System: The earthworm is almost entirely different from us and the frog because of the way their circulatory system is set up completely different from ours. They have five different hearts that have one chamber each. Also, they have only one blood vessel that goes throughout their entire body. Although their five heart are all linked together an also with the blood vessel, it has different functions in how it is passed through. They are able to get their oxygen through their skin like the frog but this is the only way they get their oxygen. They have a closed circulatory system just like us and the frog.

Crayfish

Skeletal System:The crayfish is also different from the frog and the earthworm because it has a exoskeleton. A exoskeleton is when the skeleton is on the outside of the body protecting all of it's inside. this is one of the big things that is an advantage to have your skeleton on the outside, so that it can protect itself from any outside harm. It's ligaments and muscles are attached to their bone just like how us humans are. A disadvantage of  the skeleton is that it can molt.When an organisms molt, it can vulnerable to anything that could be harmful to them. The reason is that it is exposing it's flesh and this could let organelles hurt the animal.
Muscular System:The crayfish special muscles called telson and urapod  which helps make it swim backwards. This can be helpful because it can move quickly while looking at it's prey who is behind it. The cray fish has muscles everywhere and a whole lot around it's abdomen which all have a key role in it's body.
Digestive System: The crayfish has digestive glands which produces digestive enzymes that break down the food into smaller particles in order to get more nutrients from the food. The system is not as complex as our but it still has some similar parts like the mouth esophagus and a stomach. Something that is different on them and it not in us is that they have digestive glands and we don't. What the digestive glands do is that they break down the food that they eat which is kind of like the fluid that we have in our body that breaks down our food.
Respiratory System: The Respiratory system of the crayfish is like most of the other ocean animals. It has gills which take in the water and take the oxygen inside of it and delivers it to the blood and the water is then circulated through the bronchial chamber.
Circulatory System: The crayfish is the only underwater creature that we dissected so this was the only animal that had gills. The crayfish is the only creature on this article that has a open circulatory system because all of the other animals have blood vessels. The crayfish does have a heart but the only reason they have a heart is to keep the pressure of the blood. The gills on the crayfish look like they are feathered because this give the gills more surface area,which means that it can collect more oxygen than having a solid gill.

Rat

Skeletal System:The rat has the same skeletal system like the frog but has its differences. It is a endoskeleton creature, (yes I'm saying creature because it is disgusting) so it's skeleton is on the inside of the body. It has a tail that is used for balance but it is not always a rat's friend because it can get caught in places and that is never good for any animal. It's spine is very flexible which can help move much faster and fit through places that our fat bodies couldn't fit through if it was proportioned to our size.
Muscular System: The rat's muscles mostly work in groups which is much different from us. They have a group of muscle by it's shoulder which is something that us humans don't have. The rat is very flexible which helps it move through tight places, and also has a lesser chance of being injured, which is one of the advantages of being very flexible. A disadvantage of their muscular system is that their muscles can tear or rip like our muscle. They don't have a hospital for a rat like us humans so they won't be able to know if its ripped or not but just feel the pain of it.
Digestive System:The rat has a colon which is the last part of the digestive system before the anus,which pulls salt and water from solid wastes that eventually becomes feces. The rat also has a caecum which is the part the takes away the fiber from the digested food. The duodenum which is also in the frog is the top part of the small intestine the uses digestive enzymes to break down food more. A advantage of their digestive system is much like ours and the frogs, being that it can get more nutrients from the food that it eats compared to the earthworm. A disadvantage its that there are more organs than an earthworm that can be damaged which can mess up the entire system in the way it functions. The liver is somewhat big but not as big as the frog. It still needs to be big because of the food that the rat eats and what it can do to harm the rat.

Respiratory System: The rat's respiratory system is much like ours with what it uses to get oxygen, deliver it, and how to turn it to carbon dioxide. The nostrils is a way the the rat can get oxygen into its body, another way that it gets oxygen into its body is also through its mouth. The trachea is a way that the oxygen that it inhaled can get to its lungs. The diaphragm is a way that the air inside of its body can be pushed out and can be brought in. This is another part of our respiratory system that is similar to the rat also with the trachea and nostrils. Another similar organ is the lungs which gives the air needed in the blood stream can get to the blood stream. Out of all of the four animals, the rat is the one that is almost identical to ours. 
Circulatory System: The rat is pretty much identical to us in how the circulatory system is set up. It has a  four-chamber heart that acts and does what our four-chamber heart does. This animal is also a closed circulatory system because it also has blood vessels. It has a nose and a mouth that it can breathe out of because it cannot breathe through it's skin like the earthworm or frog.