1.6 principles of circulation

Question 1

diffusion

Answer 1

the movement of the particles in a liquid or a gas down a concentration gradient from an area where they are at a relatively high concentration to an area where they are at a relatively low concentration

Question 2

concentration gradient

Answer 2

the change in the concentration of solutes present in a solution between 2 regions, ie across the cell membrane

Question 3

surface area to volume ratio

Answer 3

the relationship between the surface area of an organism and its volume

Question 4

vertebrates

Answer 4

animals with a backbone or a spinal column; they include mammals, birds, reptiles, amphibians and fish

Question 5

mass transport system

Answer 5

an arrangement of structures by which substances are transported in the flow of a fluid with a mechanism for moving it around the body

Question 6

single circulation system

Answer 6

a circulation in which the heart pumps the blood to the organs of gas exchange and the blood then travels on around the body before returning to the heart

Question 7

double circulation system

Answer 7

a circulation that involves two separate circuits, one of deoxygenated blood flowing from the heart to the gas exchange organs to be oxygenated before returning to the heart, and one of oxygenated blood leaving the heart and flowing around the body, returning as deoxygenated blood back to the heart

Question 8

systemic circulation

Answer 8

carries oxygenated blood from the heart to the cells of the body where the oxygen is used, and carries the deoxygenated blood back to the heart

Question 9

oxygenated blood

Answer 9

blood that is carrying oxygen

Question 10

deoxygenated blood

Answer 10

blood that has given up its oxygen to the cells in the body

Question 11

pulmonary circuit

Answer 11

carries deoxygenated blood to the lungs and oxygenated blood back to the heart

Question 12

why don’t single-celled organisms use mass transport systems and can use diffusion instead?

Answer 12

1. the diffusion distances from the outside to the innermost areas of cells are small
2. they have a large surface area to volume ratio, there is a relatively large surface area for materials to diffuse in and out of the cell
3. they have a low metabolic demand, the don’t regulate their own temperature and don’t use much oxygen and food to produce metabolic waste

Question 13

why do multicellular organisms need mass transport systems?

Answer 13

1. they have a large transport distance. since important exchange sites are far away from other cells within organisms, simple diffusion is not effective and would not be fast enough to meet the metabolic requirement of cells
2. they have a low surface area to volume ratio, there is less surface area for the absorption of nutrients and secretion of waste. also, greater volume means there is a longer diffusion distance
3. they have a high level of activity. larger organisms have more cells, so there is more metabolic activity. there is an increasing demand for oxygen and disposal of waste, diffusion would not be efficient enough

Question 14

what are the features of mass transport systems?

Answer 14

1. have exchange surfaces which allow materials to enter and exit the transport system
2. have a system of vessels that carry substances
3. have a way of making sure substances move in the correct direction
4. have methods for fast transportation of substances to supply the needs of the organism
5. have a suitable transport medium
6. have a way of adapting the rate of transport to the needs of the organism

Question 15

open circulatory system

Answer 15

blood is not contained within blood vessels but are directly pumped into body vessels

Question 16

closed circulatory system

Answer 16

blood is pumped around the body and is always contained within a network of blood vessels

Question 17

how does blood flow in a single circulatory system?

Answer 17

1. deoxygenated blood is transported to the gills (the gas exchange site)
2. oxygenated blood flows from the gills to the rest of the body
3. oxygenated blood flows through the capillaries where oxygen and nutrients are delivered, and carbon dioxide and metabolic waste are removed. the blood eventually becomes deoxygenated
4. deoxygenated blood returns to the heart by the atrium

Question 18

what are the 2 systems involved in the double circulatory system?

Answer 18

1. pulmonary circulation
2. systemic circulation

Question 19

what are the functions of the 2 separate circuits?

Answer 19

1. to ensure that oxygenated blood & deoxygenated blood cannot mix so the tissues receive as much oxygen as possible for respiration (maintain steep concentration gradient)
2. fully oxygenated blood can be delivered quickly to the body tissues under high pressure

Question 20

what are differences of single and double circulatory systems?

Answer 20

1. blood passes through: 2 capillary networks vs 1 capillary network
2. loss of pressure: occurs twice vs once
3. no. of times blood flows through the heart before reaching body cells: 1 vs 2
4. mixing of deoxygenated blood and deoxygenated blood: yes vs no
5. no. of chambers in the heart: 2 vs 4
6. efficiency: less vs more
7. rate of oxygen supply to cells: higher vs lower