Net primary productivity ($NPP$) is the chemical energy store in plant biomass after respiratory losses ($R$) have been subtracted from gross primary productivity ($GPP$).

The net production of consumers ($N$) can be calculated using the formula $N=I-(F+R)$, where $I$ represents energy in ingested food, $F$ represents energy lost in faeces and urine, and $R$ represents respiratory losses.

Energy transfer efficiency is typically higher between primary and secondary consumers than between producers and primary consumers because consumer biomass contains fewer indigestible materials than producer biomass.

The open ocean exhibits a higher rate of net primary productivity ($NPP$) per unit area (${g\; m}^{-2}{yr}^{-1}$) than a tropical rainforest because marine phytoplankton have a rapid rate of reproduction and lack large structural tissues.