3.1 Surface area to volume ratio

Question 1

As organisms get larger, their surface area to volume ratio…

Answer 1

decreases

Question 2

What two types of anatomical adaptations might larger organisms have to facilitate exchange (given that they have low surface area to volume ratios)?

Answer 2

1. Changes to body shape
2. Development of specialised exchange systems

Question 3

Gas exchange surfaces have large surface areas, which help improve the surface area to volume ratio of…

Answer 3

the organism.

Question 4

Features of gas exchange surfaces that increase the rate of diffusion include….

Answer 4

Large surface areas
Short diffusion distances
Systems to maintain concentration gradients

Question 5

Mammals such as a mouse and a horse are able to maintain a constant body temperature.

Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse.

(4 points)

Answer 5

A mouse, being smaller, has a larger surface area to volume ratio;

So it loses more heat per gram of body (obviously a horse loses more heat in joules than a mouse, but less PER GRAM of horse);

Metabolism generates heat;

So the mouse must have a higher metabolic rate than a horse to compensate for the extra lost heat;

Question 6

What three things are lost across surfaces specialised for gas exchange?

Answer 6

1. Waste gases (this is the point of them)
2. Water (this is unavoidable in terrestrial organisms. Terrestrial means on land, ie not aquatic - not living in water)
3. Heat (also unavoidable, if the organism is warmer than its surroundings )