Chapter 42

Question 1

Gas Exchange (2)

Answer 1

1. All organisms exchange gases with their environment
   - gases exchanged = O2 and CO2
   - carriers for O2 and CO2 in some circulatory systems, otherwise diffusion
2. Gases are mixtures

Question 2

Partial Pressure (2)

Answer 2

1. Pressure exerted by one gas in a mixture

2. When air comes in contact with water, pressure equalizes, so partial pressures in water are the same as in the air

Question 3

Exchange Media (2)

Answer 3

1. Air: viscosity and density low, PO2 high, so inefficient gas-exchange is OK
2. Water: dense and viscous, and dissolved O2 is relatively low, so it tends to be very effective

Question 4

Exchange Systems (3)

Answer 4

1. Skin may act as a gas-exchange surface
2. Restricts size (volume increases faster than surface area)
3. Most organisms have a respiratory organ with an enormous surface area

Question 5

Animal Exchange Systems (4)

Answer 5

1. Tracheal Systems
2. Gills
3. Lungs
4. Ventilation

Question 6

Tracheal Systems

Answer 6

Series of gradually smaller pipes that extend to (almost) every cell

Question 7

Gills (4)

Answer 7

1. Outfoldings of body surface
2. Blood and water flow in opposite directions (counter current; blood has lower PO2 than the water that it encounters)
3. O2 diffuses from high to low PO2 (water to blood)
4. CO2 in opposite direction

Question 8

Ventilation

Answer 8

Needed by all systems to keep O2 high and CO2 low at gas exchange surfaces

Question 9

Lungs (3)

Answer 9

1. Positive Pressure breathing: push air in
2. Negative Pressure breathing: pull air in
3. Mammals pull air in using diaphragm and rib cage

Question 10

Land Plant Exchange System

Answer 10

Leaves take up CO2 and release O2 (regulated by stomata ‘guard cells’)