Skip to content
MathsGenie logo
Open app

Course home

  1. IGCSE
  3. Biology Edexcel
  5. Question bank

Cycles within ecosystems

EasyMediumHard
1234567891011121314151617181920212223242526
Question 26

The diagram shows a representation of the nitrogen cycle. Different pathways and stages are numbered 1 to 8.

A flow diagram of the nitrogen cycle. At the top is 'atmospheric nitrogen (N_2)'. At the bottom center is 'ammonium ions (NH_4^+)'. At the middle-left is 'nitrites (NO_2^-)' and above it is 'nitrates (NO_3^-)'. On the middle-right is 'plant protein' and below it is 'animal protein'. The numbered pathways are: Arrow 1 runs from atmospheric nitrogen to ammonium ions; Arrow 2 runs from ammonium ions to nitrites; Arrow 3 runs from nitrites to nitrates; Arrow 4 runs from nitrates to plant protein; Arrow 5 runs from plant protein to animal protein; Arrow 6 runs from both plant protein and animal protein to ammonium ions (representing decomposition); Arrow 7 runs from animal protein to ammonium ions (representing excretion); Arrow 8 runs from nitrates back to atmospheric nitrogen (representing denitrification).

a.

The table lists some of the stages involved in the nitrogen cycle.

Complete the table by giving the correct number, or numbers, corresponding to each stage.

The first one (feeding) has been done for you.

StageNumberfeeding5nitrificationnitrogen fixationdenitrificationdecomposition\begin{array}{|l|c|} \hline \textbf{Stage} & \textbf{Number} \\ \hline \text{feeding} & 5 \\ \hline \text{nitrification} & \\ \hline \text{nitrogen fixation} & \\ \hline \text{denitrification} & \\ \hline \text{decomposition} & \\ \hline \end{array}Stagefeedingnitrificationnitrogen fixationdenitrificationdecomposition​Number5​​
[4]
b.

Explain how nitrates are absorbed from the soil into plant roots at stage 4.

[4]

Cycles within ecosystems Questions

  1. IGCSE
  2. /Biology
  3. /Cycles within ecosystems