circulatory systems- lqc 3

Question 1

diffusion

Answer 1

The movement of molecules or ions from a region of their higher concentration to a region of their lower concentration, down a concentration gradient

Question 2

why do some organisms not need a circulatory system

Answer 2

single celled, small so have large SA:V, all cells are close to the body surface so there is a short diffusion distance, diffusion is sufficient to supply cells with oxygen fast enough to meet oxygen demand, many have a low metabolic rate so have a low demand for oxygen

Question 3

open circulatory system

Answer 3

There are no blood vessels, instead the blood is held within a body cavity and the organs are bathed in blood. Diffusion takes place between the blood and organs. Blood is under low pressure

Question 4

closed circulatory system

Answer 4

Blood is held within blood vessels and is under high pressure

Question 5

single, closed circulatory system

Answer 5

Blood flows once through the heart during each complete circuit of the body. Blood is at low pressure when reaching the body capillaries. In a fish, the heart pumps deoxygenated blood to the gills, where gas exchange takes place (carbon dioxide diffuses from the blood into the water and oxygen from the water into the blood). Oxygenated blood leaves the gills and flows (not pumped) around the rest of the body before returning to the heart.

Question 6

double closed circulatory system

Answer 6

Blood flows twice through the heart during each complete circuit of the body. Blood is at high pressure when reaching the body capillaries. In a human, the heart pumps blood to the lungs where gas exchange takes place in the alveoli, then the blood then returns to the heart which pumps the oxygenated blood through the arteries /aorta to the rest of the body. Deoxygenated blood then returns to the heart through the veins /vena cava .

Question 7

advantages of double closed circulatory system

Answer 7

-Oxygenated and deoxygenated blood cannot mix - so tissues receive maximum oxygenated blood
-Blood can be pumped at different pressures by each side of the heart - blood travels slowly at a lower pressure through lungs and tissues, to enable efficient gas exchange and prevent damage to lung capillaries, but at a higher pressure to the body, for more efficient oxygen delivery to tissues
-Repressurisation – blood gets an extra boost when it returns from the lungs to allow the heart to pump oxygenated blood at higher pressure (faster) to the body,