3.3.1 Surface Area to Volume Ratio

Question 1

Why must organisms exchange materials effectively with their environments?

Answer 1

For survival

Question 2

List 4 examples of materials that need to be exchanged in organisms

Answer 2

1. Respiratory gases
2. Nutrients
3. Excretory products
4. Heat

Question 3

Where does exchange take place?

Answer 3

At the surface of an organism

Question 4

Describe the relationship between surface area to volume ratio and the size of organisms (1)

Answer 4

As size of organism decreases, surface area to volume ratio increases

Question 5

Write out Fick’s law

Answer 5

Diffusion rate = (surface area x concentration gradient) ÷ diffusion distance

Question 6

The rate of diffusion is lower for larger organisms.

What have larger organisms developed to counteract this problem?

Answer 6

Specialised ‘exchange systems’ such as lungs and intestines that have a larger SA:V ratio

Question 7

Explain the relationship between smaller organisms and metabolic rate.

Answer 7

Smaller organisms have larger SA:V ratio, hence, they lose more heat, to compensate, they increase metabolic activity through processes like respiration as the by products are heat - allows them to maintain body temperature.
• As SA:V ratio increases, so does metabolic rate

Question 8

Explain the relationship between smaller organisms and metabolic rate.

Answer 8

Smaller organisms have larger SA:V ratio, hence, they lose more heat, to compensate, they increase metabolic activity through processes like respiration as the by products are heat - allows them to maintain body temperature.
• As SA:V ratio increases, so does metabolic rate