The correct equation depicting the species-area relationship is:

Describe species-area relationships.

$A$: Tropical regions are more diversity-rich in comparison to temperate areas.
$R$: Availability of more solar energy directly contributes to higher productivity and species richness in these areas.

Find the odd one with respect to tropics $-$

As we move from the equator towards the poles,species diversity $.........$.

Species diversity is higher at lower altitudes than at higher altitudes because at higher altitudes: