module 3 - exchange surfaces

Question 1

SPECIALISED EXCHANGE SURFACES - why is there a need for specialised exchange surfaces in single-celled organisms?

Answer 1

• metabolic activity is low and the surface area:volume ratio is high
• diffusion is enough

Question 2

why is there a need for specialised exchange surfaces in multi-celled organisms?

Answer 2

• metabolic activity is high and the surface area:volume ratio is low
• diffusion is not enough
• the distance between the supply of oxygen and the respiring cells is too far

Question 3

list the components of an efficient exchange surfaces

Answer 3

• SURFACE AREA : provides the area needed for exchange (root hair cells, villi)
• THIN LAYERS : provides shorter diffusion distances, the process becomes fast and efficient (alveoli, villi)
• GOOD BLOOD SUPPLY : provides a steep concentration gradient as substances are constantly delivered and removed (alveoli, gills, villi)
• VENTILATION : provides a steep concentration gradient which makes the process more efficient (alveoli, gills)

Question 4

describe the components of an efficient exchange surface

Answer 4

• surface area : provides the area needed