surface area to volume ratio

Question 1

Explain the link between the size of an organism and the way in which its cells are supplied with oxygen.(6)

Answer 1

small organisms have large surface/volume ratio;
for example, single-celled organisms;
diffusion/exchange over body surface/skin;
(the need for) specialised respiratory/gas-exchange surfaces in larger animals;
diffusion is a slow process;
cells of larger organisms are a long way from gas exchange surface;
must be supplied by transport system/circulatory system/blood;

Question 2

Many large animals have blood systems. Explain why these animals need blood systems to supply their cells with oxygen.

Answer 2

Gas exchange surface long distance from (some) respiring tissues;
Blood system allows rapid transport/faster supply;
Diffusion is slow;

Question 3

Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between body mass and oxygen uptake shown in the graph.

Answer 3

Smaller animals have a large surface area to volume ratio
Lose more heat per gram of tissue
Respire faster to maintain body temperature
Oxygen demand increases

Question 4

Many of the mammals found in cold parts of Finland have a larger size and body mass than related species found in warmer regions. Explain the importance of this to their survival.(4)

Answer 4

Large animals have small surface area to volume ratio;
Large mammals are homoiothermic;
Lose less heat to environment;
By radiation/convection/conduction;
Fat;
For insulation;