Exchange in Transport

Question 1

In terms of surface area to volume ratio when is exchange the most effective?

Answer 1

Surface area must be large compared to the volume

Question 2

What are the features of specialised exchange surfaces?

Answer 2

1) Large surface area to volume ratio
2) A thin diffusion pathway
3) A partially permeable exchange surface
4) Movement of the internal/external environment

Question 3

How do insects reduce water loss?

Answer 3

Waterproof coverings, small surface area to volume ratio prevents losing water

Question 4

How are insects developed to respire?

Answer 4

They have tracheoles and spiracles which act as valves allowing gas flow.

Question 5

How are respiratory gases moved in and out of an insects tracheole system?

Answer 5

1) Diffusion- created by respiration i.e. oxygen is being used at the end of the tracheole creating a gradient
2) Ventilation

Question 6

Why do fish need a specialised gas exchange mechanism?

Answer 6

Waterproof coverings, small surface area to volume ratio prevents losing water

Question 7

What are the components of fish gills?

Answer 7

Gill filaments- stacked in a pile

Gill lamellae- at right angles to the filaments

Question 8

What mechanism do fish utilise to oxygenate themselves?

Answer 8

The counter current flow

Question 9

What are the adaptations of gill lamellae?

Answer 9

1) Large and flat
2) Large surface area
3) Rich blood supply

Question 10

What are the adaptations of the gill filaments?

Answer 10

Kept apart by water which exposes a large surface area

Question 11

What is the counter current principle?

Answer 11

1) Water passes over the gills in the opposite direction to blood
2) The water has a higher concentration of oxygen than the blood
3) Diffusion gradient is created and oxygen passes from the water to the blood

Question 12

What makes plant leaves good at gas exchange?

Answer 12

1) Short diffusion pathway
2) Large surface area to volume ratio
3) Thin and flat- larger surface area
4) Many stomata on the surface of a leaf

Question 13

What are the adaptations of roots for water transport?

Answer 13

1) Each root has many root hair cells- large SA

2) Short diffusion pathway

Question 14

What is the apoplastic pathway?

Answer 14

1) Water is drawn into root hair cells
2) Cohesive properties pulls more along
3) Cohesive tension is created which draws the water along cell walls

Question 15

What are the steps in the passage of water to the xylem?

Answer 15

1) Water from the root hair cells reaches the endodermis
2) The casperian strip prevents water passing further
3) Water is forced into the protoplast
4) Water moves into the xylem by osmosis

Question 16

What is transpiration?

Answer 16

The process which pulls water up the xylem

Question 17

What are the steps of transpiration?

Answer 17

1) Movement of water out through stomata
2) Water is replaced by water from the cell walls of mesophyll cells
3) Water from the xylem enters the mesophyll cells
4) Water enters the xylem from the roots

Question 18

What are the factors that affect the rate of transpiration?

Answer 18

1) Humidity- affects the water potential gradient between the leaf and the atmosphere
2) Wind- affects the water potential gradient between the leaf and the atmosphere
3) Temperature- (see above) also it alters kinetic energy
4) Light- stomata are closed at night

Question 19

What are the 2 factors responsible for water movement up the xylem?

Answer 19

1) Cohesion-tension

2) Root pressure

Question 20

What is the cohesion tension theory?

Answer 20

1) Water is lost by transpiration
2) Hydrogen bonds formed allows for cohesion
3) Water forms a continuous pathway from mesophyll cells through the xylem
4) As water is lost at the leaf more molecules are drawn up
5) Transpirational pull put xylem under pressure

Question 21

How do plants limit water loss?

Answer 21

1) Sunken stomata
2) Rolling of leaves
3) Thick cuticle
4) Hairy leave