Exchange and Transport

Question 1

Suggest and explain 2 features adaptations of the flatworm to allow efficient gas exchange.

Answer 1

(Thin/flat body) so a shorter diffusion pathway

(Thin/flat body) so a large surface area to volume ratio

Question 2

Name the process by which Oxygen enters the cells inside a flatworm (which has no specialised gas exchange)

Answer 2

Diffusion

Question 3

Describe how Carbon Dioxide in the air outside the leaf reaches mesophyll cells inside the leaf.

Answer 3

Carbon Dioxide enters via stoma
Stoma opened by guard cells
Diffuses through air spaces
Down a diffusion gradient

Question 4

Explain why values for the pressure in the xylem are negative.

Answer 4

Inside the Xylem has a lower pressure than atmospheric pressure / water is under tension

Question 5

Explain why the pulmonary artery is thicker than the pulmonary vein.

Answer 5

High pressure / smooths out blood flow / artery wall contains more collagen/muscle/elastin (fibres)/connective tissue

Question 6

Explain why the aorta wall changes all the time during each cardiac cycle.

Answer 6

Aorta wall stretches
Because ventricle contracts/systole / pressure rises
Aorta wall recoils
Because ventricle relaxes/diastole / pressure falls
Maintain smooth flow/pressure

Question 7

Describe how tissue fluid is formed and how it is returned to the circulatory system.

(6 marks)

Answer 7

Formation:
High blood pressure/hydrostatic pressure/ pressure filtration
Forces water/fluid out
Large proteins remain in capillary
Return: 
low water potential in capillary/blood due to plasma proteins
Water enters capillary/blood by osmosis
(Correct reference to) lymph