Exchange and Transport

Question 1

Explain how stomata in pits below leaf level reduces water loss

Answer 1

• Water vapour accumulates/increased huumidity/reduces air movement (around stomata)
• Water potential/diffusion gradient reduced

Question 2

What causes a decrease in pressure along the capillary?

Answer 2

• Loss of fluid/volume

- Friction/resistance (of capillary wall)

Question 3

Describe the ink between low concentraton of protein in blood plasma and accumulation of tissue fluid

Answer 3

• Water potential (in capillary) not as low/water potential gradient is reduced
• More tissure fluid formed (at arteriole end)
• Less/no water absorbed (into blood capillary)
• By osmosis (into blood capillary)

Question 4

Name two features of gills that allow effivient gas exchange

Answer 4

• Filaments/lamellae provide large surface area
• Thin/flattened epithelium/ short diffusion pathway (between water and blood)
• Countercurrent/blood flow maintains concentration/diffusion gradient

Question 5

Explain the relationship between body mass and Oxygen uptake

Answer 5

• Smaller animals have larger SA:V ration
• ∴lose more heat per gram of tissue
• respire more/faster (relative to body mass)
• Oxygen used in respiration

Question 6

Descirbe the importance of elastic fibres in wall of aorta

Answer 6

• Stretches/expands under high pressure/when ventricle contracts/systole
• Recoils under lowe pressure/when ventricles relax/diastole
• Smooths blood flow/maintains blood pressure/reduces pressure surges

Question 7

Explain the importance of muscle fibres in the walls of arteriole

Answer 7

• (Muscle) contracts

- (Arteriole) constricts/narrows/alters size of lumen/reduces/regulates blood flow to capillaries

Question 8

Explain why water uptake is not equivalent to the rate of transpiration

Answer 8

• (Used to provide) turgidity/support

- (Used in) photosynthesis/ (produced in) respiration

Question 9

Explain why an isotonic solution is used to dilute samples

Answer 9

• Has same water potential
• No (net) water mvement/osmosis
• Cells will no swell/burst/change in size

Question 10

Explain how moving air increases transpiration rate

Answer 10

• Removes water vapour/moisture/saturated air

- Increases water potential gradient/more diffusion/more evaporation

Question 11

Explain how an increase in temperature increases transpiration rate

Answer 11

• Increases Kinetic Energy
• Water molecules move faster
• Increases diffusion/evaporation

Question 12

Describe how the structures of the walls of arteries and aterioles are related to their function

Answer 12

ELASTIC TISSUE - Stretches under pressure (systole)
- Recoils/springs back
- Evens out pressure flow
MUSCLE - Contracts
- Redces diameter of lumen/vasoconstriction
- Changes flow/pressure
EPITHELIUM - Smooth
- Reduces friction/blood clots/less resistance

Question 13

State how palisade cells are adated for photosynthesis

Answer 13

• Chloroplasts absorb light
• Large vaccuole pushes chloroplasts to edge of cell
• Thin/permeable cell wal to absorb Carbon Dioxide

Question 14

Describe how tissue fluid is returned to the circulatory system

Answer 14

• Hydrostatic pressre lower in capillary/blood
• Water returns via osmosis
• Water potential lower in capillary/blood (due to proteins)
• (returns) via lymph (system/vessels)

Question 15

Explain the cause of root pressre

Answer 15

• Active transport by endodermis
• Ions/salts into xylem
• Lowers water potential (in xylem)
• (Water enters) by osmosis

Question 16

Why is an arteriole described as an organ?

Answer 16

It is made of (different) tissues/more than one tissue

Question 17

Describe how water enters the xylem from the endodermis in the roots and is then transported to the leaves

Answer 17

ROOT - Casparian strip blocs apoplast pathway
- Active transport of ions/salts into xylem by endodermis
- Lower water potential in xylem/water enters via osmosis
XYLEM -> LEAF - Evaporation/transpiration (from leaves)
- (Creates) cohesion/tension/negative pressure
- Adhesion/ water molecules bind to xylem
- (Creates a continuous) water column

Question 18

Describe how the removal of water from trachioles increases the rate of diffusion of Oxygen between trachioles and muscle tissue

Answer 18

• Greater surface area exposed to air
• Gases diffuse faster in air than in water
• Increase volume of air in thorax

Question 19

Explain how a countercurrent system leads to efficient gas exchange

Answer 19

• (Substance) and blood flow in opposite directions
• Maintains concentraion/diffusion gradient
• Along whole length of (area where it is taking place)