Final answer:
The correct answer is b. Surface area increases slower than volume (SA:volume ratio decreases), because as size increases, volume grows at a cubic rate while surface area grows at a square rate.
Step-by-step explanation:
As an animal's body size increases, certain changes occur in relation to surface area and volume. The increase in volume happens at a faster rate compared to the increase in surface area because volume increases as the cube of the radius, while surface area increases as the square of the radius.
This means the correct answer is b. Surface area increases slower than volume (SA:volume ratio decreases).
For example, if we consider a cell that is spherical in shape, the formula for the surface area (SA) of a sphere is 4πr², and the formula for its volume (V) is (4/3)πr³.
As the cell's radius increases, the surface area grows proportionally to the square of the radius, but the volume grows proportionally to the cube of the radius. Thus, the surface area-to-volume ratio decreases as the size of the cell increases.
This principle is essential because a lower surface area-to-volume ratio means that the cell may not have sufficient surface area to maintain adequate exchange rates (through diffusion) for the materials needed to support its larger volume.
It highlights the importance of cell division as a means to maintain efficiency in living organisms. Option b.