3.1 Surface area to volume ratio

Question 1

What happens to the surface area to volume ratio as the size of an organism increases?

Answer 1

The ratio decreases.

Question 2

How do surface area and volume change as organisms increase in size?

Answer 2

Both surface area and volume increase, but volume increases more rapidly.

Question 3

How do larger organisms provide cells with essential molecules despite a small surface area: volume ratio?

Answer 3

They have specialised exchange surfaces.

Question 4

What is the effect of the size of an organism on metabolic rates?

Answer 4

Smaller organisms have higher metabolic rates due to more heat loss from a faster rate of respiration and a larger surface area: volume ratio.

Question 5

Do small organisms have a large or small surface area compared to their volume?

Answer 5

Large

Question 6

What does it mean that small organisms have a large surface area:volume ratio?

Answer 6

• There is a large surface area for the exchange of substances
• There is a small distance from the outside of the organism to the middle of it

Question 7

What is the result of small organisms having a large surface area:volume?

Answer 7

They can exchange substances across their surfaces by simple diffusion

Question 8

The larger an organism, the _________ its surface area:volume, and the ___________ the distance from the outside to the middle.

Answer 8

Smaller, larger

Question 9

Do larger organisms have a high or low metabolic rate?

Answer 9

High

Question 10

What does the high metabolic rate of larger organisms require?

Answer 10

• Efficient transport of waste out of cells
• Efficient transport of reactants into cells

Question 11

What are some adaptations of larger organisms to increase surface area:volume ratio?

Answer 11

• Folds on villi + on microvilli -> increase surface area
• Many alveoli in each lung + branched bronchioles -> increase surface area
• Spiracles + tracheoles in insects
• Gill filaments + lamellae in fish