The function of the heart is extremely fascinating, but what is also fascinating is how many different shapes it has taken throughout evolution to get us to our human heart of 4 chambers. For my project, I did a clay model of the 4, very, basic steps that the heart has taken over the last 520 million years. The most basic structure of a circulatory system comes from fish and invertebrates, some of which don’t even have blood, but simply fluid that circulates to move nutrients. Those that do have blood flow through the body through one single pump. What was discovered, as the complexity and size of an animal grew, so did the nature of the circulatory organ. Amphibians came with a simple two-chambered heart, one deoxygenated blood and one for oxygenated blood. These two don’t yet have a formal atrium or ventricle. Reptiles came next, they developed what is considered a 2 and ½ chamber, where we see the beginnings of a separation between the atriums, and ventricles and a more complex transport line for blood flowing into and out of the oxygenated and deoxygenated halves. Our four-chambered heart, which is by no means the only model (look at an octopus) came as a way for very large and complex creatures to manage blood pressure throughout the whole system. 4 chambers, plus arteries and veins to transport the blood, which is rich in nutrients for the whole body.