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1. The organism’s body must have a high surface-area-to-volume ratio.
2. A four-chambered heart has two separate ventricles separated by a septum. This prevents oxygen-poor blood in the right ventricle from mixing with oxygen-rich blood in the left ventricle.
3. The place of gas exchange between the respiratory system and the circulatory system occurs in the alveoli of the respiratory system and the surrounding capillaries of the circulatory system.
4. The partial pressure of oxygen would be higher than that of carbon dioxide in the bloodstream after it leaves the lungs (having dropped off CO2 and picked up O2), before it enters the oxygen-starved tissues.
5. When prokaryotic cells became too large, their SA:VOL ratio decreased. In order to increase their membrane surface area to compensate for their larger volumes, eukaryotic cells evolved to have compartmentalized interiors (organelles).
6. The mammalian left ventricle has a thicker wall than the right ventricle. The left ventricle needs to be stronger because it powers the blood through the entire body (the systemic circuit). The right ventricle only needs to power the blood out to the lungs (the pulmonary circuit).
7. The respiratory system brings in the oxygen that is picked up by the circulatory system. After the circulatory system moves the oxygen to the tissues, it picks up the waste carbon dioxide the tissues generated through cellular respiration. The circulatory system moves the carbon dioxide back to the lungs, where the respiratory system expels (exhales) it from the body.
8. Blood coming from the lungs and entering the tissues has a high oxygen partial pressure. The tissues have a high carbon dioxide partial pressure because the cells have been producing a lot of carbon dioxide through the process of cellular respiration. These partial pressures facilitate the movement of oxygen from the blood into the tissues.
9. a. The more surface area exposed to the environment, the more “space” is provided for substances to pass through cell membranes.