Frogs

The two organisms discussed I this report are humans and Frogs. The Taxonomy of an organism includes kingdom, phylum, class, order, family, genus, and species. Humans are classified by the kingdom animalia, phylum chordate, class mammalia, order primates, family hominidae, genus homo, and species homo sapiens. Frogs are classified as kingdom animalia, phylum chordate, and genus and species Rana pipens. A frogs habitat is usually spent on land for most of its adult life. However frogs reproduction and development must take place in water or in a moist place. Some adaptations frogs have that aid in their survival are having thin skin that contains mucus-secreting glands. Also they have two pairs of limbs, which can be used for swimming, jumping or walking.

The anatomy of a frog is very similar to the anatomy of humans. Both humans and frogs have the same kinds of organs and systems of organs. Digestion in a frog begins in the mouth. Although the frog has teeth, they are basically useless. The frogs tongue however is very important. Most of the time the tongue is folded back toward the throat. From here the frog is able to flick out the tongue very fast to catch its prey. The tongue is also very sticky. From the frogs mouth food passes into the stomach by the esophagus. From there the food moves into the small intestine. This is where most of the digestion takes place. There are large digestive glands, the liver and the pancreas, which are attached by ducts. Liquid wastes from the kidneys go through the ureters to the urinary bladder. Solid wastes from the large intestine go into the cloaca. Both the liquid and solid wastes leave the body through the cloaca. The digestive system in humans is much more complicated. In humans digestion beings in the mouth. Once food enters the mouth chewing and saliva starts to break it up and make it easier to swallow. Then the food goes down through the esophagus to the stomach. While in the stomach, contractions of the muscular wall continue to break down food mechanically. Chemical digestion continues when acid and enzymes are secreted into the stomach cavity. Then the food passes through the small intestine. Here enzymes from the pancreas complete the chemical part of digestion. Fat is digested with bile. Bile is made in the liver and stored in the gall bladder. Whatever is left of the food, mostly liquid, enters the large intestine. Here most of the fluid is absorbed. Whatever is not absorbed is passed out of the body through the anus.

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The frog, unlike a human, has only a three chambered heart. The frog only has one lower chamber while a human has two, the right and left ventricle. The frog has one muscular ventricle and two thin-walled atria. Blood that leaved the ventricle enters a large blood vessel that branches into two atrias. These then divide into many smaller arteries, which then are divided into capillaries. Veins are used to return blood from the capillaries to the heart. The right and left pulmonary veins carry blood from the lungs to the left atrium. As the frog breaths using air with its lungs the blood is oxygenated. Blood from all the other parts of the body is brought back through three large veins into a thin-walled sac. Blood form the sac enters the right atrium. The right and left atria then empty blood into the ventricle. So therefore blood that is pumped out by the ventricle is a mixture of oxygenated blood that is from the left atrium and deoxygenated blood that is from the right atrium. Circulation in humans is a bit different. Humans have a four chambered heart. The two upper, think-walled chambers are the atria. The two lower, thick-walled chambers are the ventricles. The circulatory system consists of two major pathways. Pulmonary circulation, which is the first pathway, carries blood between the heart and the lungs. Systemic circulation, which is the second pathway, carries blood between the heart and the rest of the body. Pulmonary circulation removes carbon dioxide from the blood and adds oxygen. The only arteries that are able to carry oxygen-poor blood are the pulmonary arteries. Systemic circulation supplies blood to the liver. Capillaries and veins carrying nutrient-rich blood from the digestive organs come together to form the portal vein, leading to the liver. Blood from the liver reenters the systemic circulation through the inferior vena cava. Coronary circulation is a branch of systemic circulation. Coronary circulation supplies blood to the muscle of the heart. The coronary arteries come down both sides of the heart, which branches of going into the heart muscle. Capillaries are then formed when the arteries divide. Most blood is then drained in to the right atrium. Hepatic-Portal Circulation is also a branch of systemic circulation. Hepatic-Portal Circulation carries blood from the digestive track to the liver. This circulation helps to maintain the balance of glucose in the blood. Another type of circulation is Renal Circulation. Renal circulation is a branch of systemic circulation that carries blood to and from the kidneys. As you can see circulation in the human is much more complex than the circulation in the frog.

The Excretory system of the frog is rather simple. Carbon dioxide that is produced by the frog is excreted through its skin. The kidneys excrete other metabolic wastes that are produced by the frog. Urine is formed from wastes that are filtered from the blood. The urine from each kidney is carried by the ureters to the bladder, which is stored there temporarily. From the bladder, the urine passes into the cloaca and out of the body. In the human, excretion takes place in the large intestine. One of the main functions of the large intestine is the reabsorption of water from food. The reabsorption into the capillaries of the large intestine helps the body conserve water. The large intestine also absorbs vitamins that are produced by bacteria that normally live in the large intestine. The large intestine is also in charge of the elimination or excretion of undigested and indigestible materials from the digestive track. As this material, which consists of cellulose, bacteria, bile, and mucus, travels through the intestine it becomes feces. The rectum is where the fecal matter is stored. It is periodically eliminated through the anus.

The frogs nervous system consists of a brain, a spinal cord, and nerves. Some parts of the frogs nervous system are the same as those in the humans nervous system. Like humans, frogs have a central nervous system and a peripheral nervous system. The Frog has 10 cranial nerves that originate in the frog’s brain. Humans have 12. Also, the frog has only 10 pairs of spinal nerves. Humans have 30 pairs. In the frog the medulla regulates automatic functions such as digestion and respiration. The cerebellum controls body posture and co-ordination. The cerebrum is very small in the frog. In humans the cerebrum is very large. In the frog, nostrils are made up of two simple holes. There are complex valves, but no long nasal passages like in humans. The frogs sense of smell is made by olfactory lobes. The frogs eye is a fixed lens, so it cannot change its focus. Its eyelids do not move. To close its eye the frog brings the organ into its socket. A third eyelid or nictitating membrane may be drawn over the pulled in eyeball. The frog does not have an external ear. The eardrums and tympanic membranes are exposed. There is only one bone in the frogs middle ear. The human middle ear contains three bones. Semicircular canals help to maintain body balance in the frog, just like in humans. The nervous system, through very much like that of the frogs, is more complex. Like the frog, the humans nervous system consists of the brain, spinal cord, and nerves. Also like the frog, the human nervous system is divided into the central nervous system and the peripheral nervous system. The lower parts of the brain control basic functions such as breathing, heart rate, body temperature, hunger, and thirst. The major parts of the brain are the cerebrum, cerebellum, and the medulla. The cerebrum is the largest part of the human brain. This is much bigger than the frogs. The cerebrum is divided in half from front to back by a deep grove, which separates the cerebrum into the right and left cerebral hemispheres. The cerebellum controls all voluntary movements and some involuntary movements. The medulla is made mainly of nerve fibers that connect the spinal cord to other parts of the brain. This controls many of the involuntary activities including breathing, heartbeat, blood flow, and coughing. A reflex is an involuntary, automatic response to a given stimulus. There are a lot of body functions that are controlled by reflexes. Some examples of these are blinking, sneezing, coughing, breathing movements, heartbeat, and peristalsis. A reflex arc is the pathway over which the nerve impulses travel in a reflex. The eye is one of the human sense receptors. The white part of the eye is called the sclera. This helps to give the eye shape and projects the inner parts of the eye. Light enters the eye through the cornea. Unlike the eye of a frog, a human eye has a lens, which is able to focus the light on the back of the innermost layer, which is called the retina. The human ear has two sensory functions. One is hearing, and the other is helping to keep balance. The three parts of the ear are the outer ear, the middle ear, and the inner ear. The receptors for smell are the olfactory cells.

The respiratory system of the frog includes the lungs, the lining of the mouth, and the skin. All of these have moist, think surfaces and blood vessels. The frogs skin is composed of two layers, an outer epidermis and an inner epidermis. Blood vessels run throughout the frogs skin. Oxygen can pass through the skin, entering directly into the blood. When the frog is in water all its respiration takes place through the skin. Oxygen can be obtained right from the water. The frog doesnt just breath through its skin, it has paired lungs. Just like in humans air enters the body through two nostrils, passes through the windpipe, and is received by the lungs. The difference in the way the frog breathes from the way humans breath is that in humans breathing is aided by ribs, the diaphragm, and chest muscles. In the frog there are no ribs or diaphragm. And the chest muscles that the frog does have are not involved in breathing. In the human respiratory system takes in oxygen from air, and excretes carbon dioxide and water vapor. Air enters the nose and mouth and travels through the larynx and trachea. The trachea divides to enter each of the two lungs, and then divides more than 20 times to form a very large number of small air sacs. Oxygen from the air then enters the blood through capillaries in the walls of these air spaces, and the blood releases carbon dioxide into the air spaces to be exhaled.
The Human endocrine system consists of many endocrine glands. The anterior pituitary gland is a growth hormone. If it is over secreted its effects can include giantism in children. In adults effects include acromegaly. If it is under secreted its effects can include dwarfism. Another gland is the adrenal cortex gland. This gland is an aldosterone, cortisol hormone. If it is over secreted its effects can include Cushings disease. If this hormone is under excreted Addisons disease can result. Another gland is the Thyroid gland. The hormone secreted from this gland is thyroxin. Hyperthyroidism can result if this hormone is over secreted. If this hormone is under secreted cretinism can occur. Another gland is the pancreas. Insulin is the hormone that is secreted from this gland. Diabetic shock can occur if this hormone is over secreted. Diabetes can occur if insulin is under secreted.

The reproductive system in the frog is different in the male and the female. In the female, the ovaries are located along the back. There are a large numbers of eggs, which are produced by the ovaries that enter the oviducts, which are coiled tubes. The eggs are stored in the sacs at the base of the oviducts. They are stored there until they are released from the body through the cloaca. In the male, the testes are small, bean shaped, yellowish organs that are also just above the kidneys. Sperm is produced in the testes and then pass to the kidneys through microscopic tubules. From the kidneys, the sperm are carried by the ureters to the cloaca. The sperm are discharged from the male through the cloaca during mating. The human reproductive system is also different in the male and female. The male gonads are the testes, like in the frog. The testes make sperm. Sperm are the male gametes. The testes also make the male sex hormone testosterone. Fluid produced by the seminal vesicles, prostate gland, and Cowpers glands mix with sperm to form semen. Each testis made up of small, coiled tubes called the somniferous tubules. From there, the immature sperm pass through the epididymis, which is a storage area on the upper rear part of each testis. The vas deferens is a tube that leads upward from each testis into the lower part of the abdomen. The two vas deferens empty into the urethra. The female reproductive system is somewhat like that of the frogs. In the female reproductive system the ovaries produce the female sex hormones estrogen and progesterone. In the ovaries eggs mature in the follicles. Fertilization may occur when the follicle breaks and the egg is released into the oviduct.

Locomotion in the frog is similar to that of locomotion in humans. Frogs use jointed appendages. The frogs legs are extremely muscular are sometimes compared to human arms. Unlike the human, a frog only has four fingers, which are webbed together. They are webbed together because they often have to get around through the water. The webbed feature allows for easy swimming. A frog uses all four appendages to get around. Usually by hopping. A human only uses two, their legs.

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