Surface Area To Volume Ratio (3.3.1)

Question 1

How do single-celled organisms carry out exchange of substances?

Answer 1

• Substances can diffuse directly into our out of the cell across the cell-surface membrane
• This is effective because they have a large surface area to volume ratio and short diffusion pathway

Question 2

What is the relationship between the size of an organism and the surface area to volume ratio?

Answer 2

• As the size of an organism increases their surface area to volume ratio decreases

Question 3

How have larger organisms adapted to overcome a small surface area to volume ratio?

Answer 3

• They have developed specialised exchange structures to maintain adequate rates of gaseous exchange

Question 4

What is the relationship between surface area to volume ratio and metabolic rate in organisms?

Answer 4

• Smaller organisms have a larger surface area to volume ratio, resulting in more heat loss per gram of body mass
• To maintain a constant body temperature, they require a higher rate of respiration to generate enough heat
• Therefore, they have a higher metabolic rate