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Comparing Humans and Crocodiles

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Ian Cullings

on 5 June 2013

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Transcript of Comparing Humans and Crocodiles

Comparing Humans and Crocodiles By Ian Cullings Humans Crocodiles Gas Exchange The respiratory system, which carries out all of the gas exchange in humans, consists of the nose, pharynx, larynx, trachea, bronchi, and lungs Air is pulled into the nose or mouth first, and is pulled down the Pharynx (or throat), which is a long tube which connects to the larynx The larynx contains your vocal cords, which allow you to make noises, and is also a passageway from the pharynx to the trachea Then air continues down the trachea, or windpipe, and down one of two tubes called bronchi. A piece of cartilage known as the epiglottis covers the entrance to the trachea when you swallow food or water so it does not go to your lungs and damage them These bronchi divide into smaller and smaller bronchi, known as bronchioles, and air passes through each of these millions of tiny tubes Finally each of the bronchioles reach a alveoli, a tiny air sac usually found in clusters. Each lung contains about 350 million The oxygen dissolves in the moisture in the alveoli, and diffuses through the capillaries into the bloodstream. Hemoglobin carries oxygen through the bloodstream for efficiency, so each blood cell can carry over 60 times more than it could without hemoglobin Each of the lungs is a sealed sac, with a large muscle at the bottom known as the diaphragm at the bottom When you breath in, the diaphragm contracts to increase the area of the chest cavity, which creates a partial vacuum, allowing air to fill the lungs from the mouth When you breath out, the diaphragm pushes up into your lungs, forcing the air from your lungs. When you need more force, other muscles surrounding the lungs can also push into it Crocodiles have a trachea which connects air taken in by the mouth or nostrils to their lungs. However, crocodiles have a palate which seperates their breathing and eating tubes, allowing them to breath while eating Another rigid palatal flap prevents water from flowing down their gullets, allowing them to swim with their mouths open Crocodiles lungs also have alveoli, as with humans. When a crocodile breaths in, a process known as inspiration moves the liver and other organs beneath the lungs away from the lungs, towards the tail to allow air to enter the lungs with the vacuum created The opposite process, known as expiration, consists of the liver and other organs moves towards the lungs, forcing the air out of the lungs A unique muscle attached to the liver and viscera known as the diaphragmaticus aids in inspiration and expiration. Similarities and Differences Gas Exchange Both crocodiles and humans take in air through their mouth and nostrils, which continues down their trachea and esophagus and into their lungs. They also both have alveoli in their lungs, which allow the oxygen taken in to be moved through the bloodstream However, in humans, the diaphragm contracts to allow oxygen to enter and leave the lungs, while in crocodiles many of their internal organs are pressed into and out of the lungs to do this very task. Also, crocodiles have a palatal flap covering their esophagus and trachea, which although it is a different organ, is very similar to the epiglottis in humans, only adapted for swimming. Transport The human circulatory system contains the heart, blood vessels, and the blood which flows throughout them The heart is almost completely muscle, and enclosed a a sac of tissue known as pericardium The walls of the heart "sandwich" a thick muscle known as myocardium, whih pumps blood throughout the body The heart contracts about 72 times per minute, pumping 70 milliliters The divider between the right and left walls of the heart is known as the septum, which prevents the oxygenated blood from mixing with the blood lacking oxygen The heart has two atria (the upper chambers) and two ventricles (the lower chambers) Blood enters for the left and right atria, and when the heart contracts, the blood flows to the ventricles Flaps of tissue called valves allow blood to flow to the ventricles, but close after blood flows in to prevent it from flowing back The pace of your heart is set by one of to fibers (one for atria and one for ventricles) which, when stimulated cause the other muscles in your heart to be stimulated, setting your heartbeat (or the rate at which your heart contracts). Your heart beats faster or slower depending on your need for oxygen Once blood leaves the heart, it passes to the aorta, a large blood vessel. From their, it flows to your arteries, capillaries, and veins Capillaries are the smallest blood vessels, and they bring the oxygen to each cell and remove the waste products to be brought to the kidneys for waste disposal The veins return the blood to the heart after it has be deoxygenated Digestion Digestion begins with the mouth, where food is broken down by the teeth and saliva is added by the salivary glands Saliva contains an enzyme known as amalayse, which break down starches in food Food then continues down the throat and esophagus, where it is pushes down into the stomach by contractions known as peristalsis Food passes through the cardiac sphincter to leave the esophagus into the stomach, which closes afterward to prevent the contetns of the stomach from damaging the esophagus Inside the stomach, hydrochloric acid and other enzymes are secreted from the walls, which are protected from it by a thick layer of mucus The acid activates a enzyme known as pepsin which is secreted from the walls, which allows protein to be broken down. After digestion occurs, the remaining liquid is known as chyme. It is pushed through the pyloric valve into the small intestine from the stomach In the small intestine, the chyme is mixed with digestive fluids and enzymes made by the liver, pancreas, and the linign of the start of the small intestine, known as the duodendium The chyme is broken down more by these enzymes and continues down to the second section of the small intestine Many of the nutrients are absorbed by villi, tiny, hairlike projections on the walls of the small intestine Once almost all of the nutrients have been absorbed by the small intestine, the remainder is pushed to the large intestine The main purpose of the large intestine is to remove the water from the undigested material Water is absorbed by the walls of the large intestine and used in other parts of the body Bacterial colonies grow on the undigested material, which provide useful vitamins for the body and aid in the digestive process Waste Removal The skin, lungs, and kidneys are all part of the excretory system The kidneys, are about 2-3 inches wide, and have a tube known as the ureter leaving each of them which carry urine to the urinary bladder, and organ where urine is stored before being excreted Waste filled blood flows to the kidneys and is cleaned inside. The clean blood is sent back into the bloodstream to be used again. Another important part of the excretory system is the anus, which is where the remainder of the food that cannot be digested exits body after the large intestine There are about one million nephrons inside each kidney, tiny units with remove the wastes from the blood.
Each nephron contains a tiny blood vessel known as a glomerulus and a tiny urine collecting tube called a tubule The glomerulus acts as a filtering unit, passing wastes though to the tubule and keeping normal proteins and cells in the bloodstream Water Balance The kidneys also maintain the water balance of the body. they do this in the bowman's capsules. When filtration occurs, the water in the bloodstream becomes part of the filtrate. Then, when reabsorption occurs, the filtered substances leave through the renal tube, and the water follows due to osmosis. When you drink water, the kidneys decrease water reabsorption, causing less water to be returned by the kidneys and more to be sent to the urinary bladder. If not for this process, your cells would swell and burst from the effects of osmosis If you digest more salt, the kidneys cause less salt to be reabsorbed into the bloodstream, and the excess salt in excreted as urine Reproduction Reproduction begins in humans with puberty, a period of rapid growth and sexual maturity, along with the production of testosterone in males and estrogen in females. In males, sperm (the male gamete) is produced. The consist of a head containing a nucleus (with the information to help create a offspring) and a mitochondrial powered tail allowing it to swim to the female gamete The female gamete is known as an egg and is produced in the ovaries. Once roughly every 28 days, a eg is released from the ovaries down the fallopian tubes. During sexual reproduction, sperm are released into the woman's vagina, and swim up the fallopian tubes to hopefully meet an egg cell. With millions of sperm cells released, their is a good chance one will find the egg cell. Once a sperm finds an egg cell, the nuclei merge to become one cell This cell finds its way to the uterus, where the fetus begins to develop by mitosis. Over time, the embryo forms, fueled by nutrients taken in by the mother After the 9 month gestation period, the baby is ready to be born. Muscles in the uterus wall are stimulated by hormonal release. Contractions occur known as labor and the amniotic sac breaks, and contractions force the child out of the vagina. From there, the child develops on its own Transport Crocodiles have a four chambered heart simliar to humans and birds, with two atria and two ventricles, however, they can completely shut off a ventricle to save oxygen and allow them to dive for longer periods of time The two ventricles in a crocodile's heart are completely separated, allowing for different pressures for blood returning the lungs or leaving to the rest of the body. Their heart completely separates oxygenated and deoxygenated blood The different pressures allow them to move blood quickly through their body without endangering their alveoli. The crocodile heart is thought to be the most efficient and complex heart known to science Crocodiles also have a special valve which allows the to cut off blood to the lungs, and the extra blood is shot from the left aorta to the right aorta Digestion Crocodiles have the most acidic stomach of any vertebrate, allowing them to digest bone, hooves, and horns Some swallow stones to aid in digestion and to act as ballast Crocodiles have developed sharp teeth to grab onto prey and tear, a large part of their hunting Their stomach resembles that of birds, with a gizzard, unlike other reptiles. A crocodile's stomach contains two chambers, one grinds up food while the other contains a digestive system which remove nutrients Crocodiles swallow their food whole if possible, other wise they tear their food into smaller chunks. Reproduction Crocodiles reproduce by laying eggs, like all other reptiles Mating takes place in the water Crocodiles do not have sex chromosomes, instead the gender depends upon the temperature of the eggs At 30 degrees Celsius they are males, at 31 they are both sexes, at 32 degrees they are males, and at 33 they are females. Incubation period is about 80 days Females can store sperm until conditions are right. Waste Removal Crocodiles lack a urinary bladder, instead they excrete it directly after it is removed from the bloodstream by the kidneys Crocodiles have three kidneys which are developed early in embryonic development Crocodiles excrete nitrogenous wastes in liquid form, with liquid between 40% and 70% ammonia Water Balance Saltwater crocodiles get their drinking water from their food, they cannot drink saltwater Salt glands in mouth excrete salt and potassium to maintain electrolyte and internal water balance while out of water, and become larger or smaller depending on the level of salt in the water Transport Crocodiles and humans have very similar hearts, each with four chambers. However, crocodiles can shut off one of their ventricles to save oxygen, unlike humans Both crocodiles and humans have different pressures in their hearts, so they can quickly pump blood without damaging the alveoli in the lungs Crocodiles have a special valve which humans do not, it allows them to completely cut off blood the their lungs to save oxygen when they are underwater Digestion Both humans and crocodiles have a stomach which connects to their mouth by their esophagus, where nutrients are digested However, a crocodiles stomach is divided into two, one which breaks down the food, and the other which takes in nutrients A crocodile also only has one intestine, which does the job of both the large and small intestines in humans A crocodiles stomach is much more acidic than a humans, due to the food it eats. Waste Removal Both humans and crocodiles filter nitrogenous wastes through their kidneys, however, crocodiles have three sets of kidneys while human have one While humans excrete wastes as urea, crocodiles excrete their nitrogenous wastes as uric acid. However, in humans urine is first sent to a urinary bladder, while in crocodiles it is excreted directly after being filtered from the bloodstream Water Balance In both humans and crocodiles kidneys take care of most of the water balance However, crocodiles have salt glands which help them balance the salt from the salt water Reproduction While both crocodiles and humans both reproduce heterosexually, crocodiles lay eggs while humans birth live offspring Also, humans have sex chromosomes while crocodiles do not. Blood flows into the nephron from the glomerus and, as it is under pressure, it filters through the capillaries and into the bowman's capsule. Glucose, salts, amino acids and some vitamins are filtered through, while the plasma remains because of its size.

The remaining waste is excreted as urea. Gas Exchange Works Cited "Nile Crocodile Fact Sheet." Nile Crocodile Fact Sheet. San Diego Zoo Global, 01 May 2010. Web. 15 May 2013. Hosking, Chris. "Freshwater Crocodile - Australian Museum." Freshwater Crocodile - Australian Museum. Australian Museum, 01 Nov. 2010. Web. 15 May 2013. "The Reptipage: Crocodylian Bodyplans." The Reptipage: Crocodylian Bodyplans. N.p., 07 Sept. 2012. Web. 15 May 2013. "reptile." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2013. Web. 30 May. 2013. <http://www.britannica.com/EBchecked/topic/498684/reptile>. Britton, Adam. "Crocodilian Biology Database - General Biology." Crocodilian Biology Database. Adam Britton, n.d. Web. 15 May 2013.
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