Animal Circulation AP Biology Unit 6

Invertebrates with Gastrovascular Cavities Don ’ t have a true circulatory system Material exchange (gases, nutrients, wastes) with the environment occurs through diffusion Why is diffusion effective here? –The animals are only a few cell layers thick– materials don ’ t have to go across too many layers Example: Cnidarians

True Circulatory Systems 3 main components in a true circulatory system: 1.Circulatory fluid (blood) 2.Tubes to transport fluid (blood vessels) 3.Muscular pump (heart)

True Circulatory Systems Blood pressure keeps the circulatory fluid moving through the system (in addition to other forces) Blood pressure = force exerted on the walls of the blood vessels by the blood (caused primarily by the pumping of the heart)

True Circulatory Systems In general, higher metabolism means a more complex circulatory system An animal either has an open or a closed circulatory system

Open Circulatory Systems Blood and interstitial fluid are the same (hemolymph) Low blood pressure (less energy to circulate fluid) Simple system of tubes The heart helps pump hemolymph around Hemolymph will also be pushed back into the tubes as the animal moves around

Closed Circulatory System Blood is confined to tubes, so it is different from interstitial fluid Molecules diffuse between blood and interstitial fluid High blood pressure

Question… Why would higher blood pressure be beneficial? –Can get blood to areas that need it more efficiently –Allows the organism to be more active

Closed Circulatory System Complex system of tubes arteries = vessels that carry blood away from heart veins = vessels that carry blood to heart capillaries = tiny, porous vessels through which molecules diffuse in / out (throughout body)

General Circulatory Pathway Heart  artery  capillaries  vein  back to heart

Comparison of Vertebrate Circulation Gas exchange (CO 2 and O 2 ) with the environment across a variety of locations Blood pressure is highest in the blood vessel leaving the heart

Comparison of Vertebrate Circulation- Fish Blood in the heart is separated (oxygenated and de-oxygenated blood are not mixed together) Single circulation = blood goes to the heart once (continues on to the body without returning after the gills) 2 chambers in heart (1 atrium, 1 ventricle)

Comparison of Vertebrate Circulation- Amphibian Blood in the heart is mixed– deoxygenated and newly oxygenated blood mix together in ventricle Double circulation = blood is pumped two times from the heart– goes to the lungs, then comes back to get pumped to the rest of the body 3 chambers in heart (2 atria, 1 ventricle)

Comparison of Vertebrate Circulation- Reptile Blood in the heart is mixed-- deoxygenated and newly oxygenated blood mix together in partially separated ventricle Double circulation 3 ½ chambers in heart (2 atria, one partially separated ventricle) –Only crocodiles have fully separated ventricles

Reptile Circulation Reptiles also have a 2 nd aorta Benefit? –Can bypass the lungs when underwater (no point in sending blood to the lungs if there can ’ t get O 2 from them) –Blood continues to flow to the body tissues (so they can still get some O 2 )  higher activity

Comparison of Vertebrate Circulation- Mammal & Bird Blood is separated – held in separate chambers Double circulation 4 chambers in heart (2 atria, 2 ventricles)

Question… Why is having separated (compared to mixed blood) an advantage? –If blood is mixed, then deoxygenated blood that hasn ’ t gone to the lungs will also return to the body –Separated blood means that the blood returning to the body is all fully re-oxygenated

Pressure and Metabolism The inability to maintain pressure over a distance yields lower metabolism. –Pressure decreases as blood flows through tiny capillaries Which organism can have the highest metabolic rate? –Mammals and birds (in general)

Question… What is the benefit of having double circulation (compared to single circulation)? –Blood can reach tissues more efficiently  High blood pressure –This allows the organism to be more active