According to Fick's Law, the rate of diffusion is proportional to:
Surface Area×Difference in ConcentrationDiffusion Distance \frac{\text{Surface Area} \times \text{Difference in Concentration}}{\text{Diffusion Distance}} Diffusion DistanceSurface Area×Difference in ConcentrationWhich of the following statements correctly describes a structural or physiological adaptation of an organism's gas exchange surface and its direct effect on one of these variables?
The counter-current flow system in the gill lamellae of bony fish maintains a concentration gradient (ΔC\Delta CΔC) along the entire length of the exchange surface, preventing oxygen levels from reaching equilibrium.
The thin, flattened shape of squamous epithelial cells in the alveoli and capillaries reduces the surface area (AAA) of the exchange barrier to accelerate diffusion.
The secretion of surfactant by alveolar cells increases the surface tension of the fluid lining the alveoli, thereby maximising the total surface area (AAA) for gas exchange.
A dense capillary network slows down blood flow around the alveoli so that oxygen levels in the blood can equalise with those in the alveolar air, which increases the concentration gradient (ΔC\Delta CΔC).
