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Download Evolution of the Circulatory System
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Evolution of the Circulatory System Open vs Closed System • Open Circulatory System • Exists in invertebrates • Insects, mollusks some crustaceans • Blood vessel pumps blood through peristalsis to large sinuses where organs are bathed in blood. • Only works in small organisms where cells are close to environment. Insects were huge during the carboniferous period! Open vs Closed Circulatory System • Closed System • Found in some invertebrates and higher order organisms • Blood pumped through closed system of arteries, veins and capillaries • Blood pumped directly to organs • Allows for regulation of blood flow • Increased pressure and speed of blood flow • Allows for larger organisms with cells farther from the environment Evolution of the heart • Hearts can be found in animals with 2, 3 and 4 chambers. 2 Chambered Heart • Found in fish • One atria and one ventricle • Blood pumped to gills to pick up O2 and then travels to organs and then back to heart. • Low blood pressure • Single Circulation 3 Chambered Heart • Found in reptiles and amphibians • 2 atria and 1 ventricle • 1 atria deoxygenated blood from body 1 atria oxygenated blood from lungs. • Single ventricle pumps blood out to both lungs and body. • Oxygenated and deoxygenated blood mixed In ventricle causing dilute O2 blood. 4 Chamber Heart • Birds and mammals • 2 atria and 2 ventricles • Oxygenated and deoxygenated blood kept separate. • Allows for increased blood pressure, thermal regulation and sustained muscle movement.
