Transfer of Energy and Matter · Paper 1 — Free Biology HL Practice Questions

A farmer applies an ammonium-based fertilizer to a maize crop. Soil bacteria oxidize the ammonium ions ($\text{NH}_4^+$) first to nitrite ions ($\text{NO}_2^-$) and then to nitrate ions ($\text{NO}_3^-$), which are absorbed by the maize roots. Which process carried out by these soil bacteria directly produces the $\text{NO}_3^-$ available to the plant?

A sealed glass jar containing damp soil and a small plant is placed on a sunny windowsill. Water droplets form on the inside of the glass lid. Which two water-cycle processes are directly responsible for the formation of these droplets?

In a freshwater lake ecosystem, phytoplankton fix $20\,000 \ \text{kJ m}^{-2} \text{yr}^{-1}$ of solar energy. Zooplankton ingest $4\,000 \ \text{kJ m}^{-2} \text{yr}^{-1}$ but assimilate only $2\,000 \ \text{kJ m}^{-2} \text{yr}^{-1}$. Applying a trophic efficiency of 10%, what is the expected energy assimilated by the secondary consumers?