1. In humans, the heart has four chambers: two upper chambers (the atria) and two lower ones (the ventricles). The right atrium and right ventricle together make up the "right heart," and the left atrium and left ventricle make up the "left heart." A wall of muscle called the septum separates the two sides of the heart.The heart functions by pumping blood both to the lungs and to the systems of the body. To prevent blood from flowing backwards or regurgitating back into the heart, a system of one-way valves are present in the heart. The heart valves can be broken down into two types: atrioventricular and semilunar valves.

2. One can say that the reptile heart has three chambers, two atria and one, partially divided,ventricle. Or one may argue that reptiles have four chambered hearts with two atria and two ventricles, but the wall between theventricles is incomplete. In fact, both of these interpretations are correct. Though, as a result of the incomplete partition between the two ventricles, there is some mixing of oxygenated and deoxygenated blood, this is minimized by the timing of the contractions. 3. The crocodile is the lone exception among reptiles in terms of heart structure. In the crocodile heart the partition between the right and the left ventricle has been completed and resembles the four-chambered heart of birds and mammals. Nevertheless a peculiar difference from the four chambered hearts does exist. Specifically, the right ventricle pumps blood into not one but two separate vessels: the pulmonary artery and the, socalled, right systemic artery. Such an arrangement allows the crocodile to effectively switch between normal and low oxygen (apnea) conditions by closing the 4. The heart of fish are the simplest vertebrate hearts. They are made up of two main chambers: a thin walled atrium, and a more muscular ventricle. The atrium pumps the blood into the ventricle, which in turn pumps the blood into the conus, an elastic compartment which does not pump, but has the ability to stretch and squeeze. From the conus the blood travels straight to the gills where it is enriched with oxygen. The oxygenated blood then flows through the body and returns to the atrium.The fish therefore has a singlecurcuit circulation through which blood is driven by a simple twochambered heart. 5. HUMANREPTILESFISHFour chamber -Two atrium -Two ventricleThree chamber (except for crocodile) -Two atrium -One ventricleTwo chamber -One atrium -One ventricleDouble circulatory systemDouble circulatory systemOne circulatory systemComplete ventricular septumIncomplete ventricular septumNo septumSinus venosus exists distinctly only in the embryonic heartConsist of sinus venosusConsist of Sinus venosus 6. Reptile (except for crocodile) has three chamber heart compare to human, which is consist of four chamber of heart Reptiles (except for crocodile) has only one ventricle while human heart consist of two ventricle. Reptiles has incomplete ventricular septum while human has complete ventricular septum Reptiles has mixing of oxygenated blood and deoxygenated blood due to incomplete septum, while human has seperate of oxygenated blood and deoxygenated blood. Reptiles consist of sinus venosus while human, sinus venosus exists distinctly only in the embryonic heart 7. Fish has two chamber of heart while reptiles has three chamber of heart (except for crocodile) and four chamber of heart for crocodile reptile Fish has only one atrium while reptiles has two atrium Fish has only one ventricle while crocodile reptile has two ventricle Fish has one criculatory system while reptile has double circulatory system Fish do not has septum while reptiles has incomplete ventricular seeptum 8. Human heart consist of four chamber while fish heart only consist of two chamber Human heart has two atrium while fish heart has one atrium Human heart has two ventricle while fish heart has one ventricle Human has double circulatory system while fish has one circulatory system Human has complete ventricular septum while fish do not has any septum Human only has sinus venosus during embryo period only while fish indeed have a sinus venosus 9. An organ that pumps blood throughout the body via the circulatory system. Consist of chamber; atrium and ventricle. Consist of circulatory system. Consist of blood vessel Consist of valve Contracts and expands Involved of oxygenated blood and deoxygenated blood 10. Crocodile is a type of reptiles. Crocodile has 4 chamber of heart. Two of them known as atria and other two chamber known as ventricle. This characteristic actually same with humans heart Both human and reptiles heart has double circulatory system. Both consist of septum 11. Both has only one ventricle (reptiles except for crocodile) Both has sinus venosus