Adaptions to Surface Area to Volume Ratio

Biology: Cambridge International A Level, topic 4.2.6

Adaptations to Surface Area to Volume Ratio

Some organisms have evolved adaptations that allow them to overcome a decrease in surface area to volume ratio. These adaptations include:

A large surface area allows more of a substance to diffuse at the same time.
Prokaryotic organisms have enormous SA:V, allowing them to meet the cell’s energy requirements through respiration that occurs across the plasma membrane only.
Eukaryotic cells are far larger so have a smaller SA:V, this necessitates the need for specialist organelles for respiration (mitochondria) that have huge membrane surface area in which enough proteins for respiration can be embedded to meet the larger cell’s needs.

Some organisms have transport systems that move substances around the organism or facilitate exchange.
E.g. Blood vessels, lungs, gills, xylem.
Transport systems allow a higher concentration gradient to be maintained.
A steep concentration gradient increases the rate of transport.
Transport systems also allow substances to move closer to the cells that need to exchange them.

Some large animals have adaptations that allow heat to be transferred more efficiently.
E.g. Elephants have large, highly vascularised ears that allow heat to be transferred rapidly.
Lower latitudes have warmer climates so the animals that live there need to transfer heat to the surroundings in order not to overheat. Animals living in the polar regions must try to conserve as much heat as possible due to cold external temperatures.
A general trend in animal biology is for occupants of equivalent niches in low latitudes to be smaller than their high latitude counterparts. This is because smaller animals have larger SA:V so can transfer heat to the surroundings more efficiently.

What is the adaptive advantage of a thin membrane?
Which of these statements about surface area to volume ratio adaptations are true?