Fig. 1 shows part of the nitrogen cycle in a community garden. Pea plants grow in one bed and lettuce plants grow in another. The gardener adds compost made...
Question 1 Report
Fig. 1 shows part of the nitrogen cycle in a community garden. Pea plants grow in one bed and lettuce plants grow in another. The gardener adds compost made from dead leaves and vegetable peelings. Bacteria in the soil carry out several processes. The arrows show how nitrogen goes between the atmosphere, soil and organisms.
(a) Complete the diagram by naming process A. [1]
(b) Complete the diagram by naming process B. [1]
(c) Explain why nitrate ions in the soil can decrease when lettuce plants are growing rapidly. [2]
(d) State why the gardener should avoid removing all dead plant material from the garden. [2]
(e) Describe the role of denitrifying bacteria in the nitrogen cycle. [2]
Answer Details
(a) Process A is nitrogen fixation. Nitrogen-fixing bacteria convert nitrogen gas from the atmosphere into nitrogen compounds that can enter the soil and plants. [1]
(b) Process B is decay or decomposition. [1]
(c) Rapidly growing lettuce plants absorb nitrate ions through their roots. The ions provide nitrogen for making amino acids, proteins and new cells, so soil nitrate concentration can decrease. [2]
(d) Dead plant material supplies material for decomposers to break down. This returns nitrogen compounds, including nitrate ions, to the soil for later uptake by plants. [2]
(e) Denitrifying bacteria convert nitrate ions or other nitrogen compounds in soil into nitrogen gas. The nitrogen gas is released back into the atmosphere. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
