Topic 3 - SA:V Ratio

Question 1

Small organisms have a larger or smaller surface area to volume ratio

Answer 1

Larger

Question 2

How to single celled organisms exchange substances?

Answer 2

Diffusion across the cell membrane directly into or out of the cell

Question 3

Give two reasons why in multicellular organisms diffusion across out of membranes would be too slow

Answer 3

The diffusion distance is too large due to internal organs as well as a low surface area: volume ratio

Question 4

What two things do gas exchange surfaces have that increase the rate of diffusion?

Answer 4

Small diffusion distance and a large surface area

Question 5

What does Fick’s Law state?

Answer 5

Rate of diffusion ∝ (surface area x concentration) / distance

Question 6

What is surface area?

Answer 6

The total area of the organism that is exposed to the external environment.

Question 7

What is volume?

Answer 7

Total internal volume of the organism.

Question 8

What is the need for specialised systems?

Answer 8

1) Supply of oxygen - organisms require ATP in order to carry out the biochemical processes required for survival.
2) Removal of CO2 - CO2 is a toxic waste product of aerobic respiration. If it accumulate in cells/tissues it alters the pH.