Unit 10 Test
Body Size and Surface Area
Exchange with the environment and the amount of material that must be exchanged are
both strongly influenced by body size and surface area.
The larger the animal, the greater its absolute requirements are for gases and nutrients.
Relationship Between body size and metabolism
On the left, the positive relationship between body size and absolute metabolic requirements: bigger
animals need more food, oxygen, etc. in total amount.
On the right, the negative relationship between body size and relative metabolic requirements: per gram
of tissue, smaller animals require more food, oxygen, etc
Surface area to volume ratio
This is the amount of surface area exposed to the environment relative to the total volume of the object.
Smaller objects have higher surface area to volume ratios than larger objects.
Bigger body size means lower surface area to volume ratio, which means less efficient exchange with the
When more surface area is needed, organs may have specialized structures that increase total area such
as extensive folding in the membranes in the digestive, respiratory, and circulatory systems.
Metabolic Rate and Temperature
Metabolic rate is the overall indication of how much energy or 2 is being consumed per unit time.
In ectotherms, a decrease in environmental temperature decreases body temperature and in turn, the
overall metabolic rate. Therefore, less2O will be consumed per unit time at lower temperatures. Temperature quotient or “Q ” which describes the change in
rate with an increase in temp