Theory question 104
Soil Fertility and Plant Nutrition(a) With the aid of a fully labelled diagram, describe the carbon cycle.
(b) Explain the importance of carbon cycle to crops and animals.
Show the model answer
Model answer
(a) Labelled diagram: CO2 in the air → taken in by green plants in photosynthesis → carbon in plant tissues → eaten by animals → returned to air by respiration of plants and animals; dead plants and animals decomposed by micro-organisms release CO2; burning of fuels/vegetation releases CO2; some carbon stored as fossil fuels
(b) Supplies CO2 for photosynthesis (food for crops); provides food (carbohydrates) for animals; keeps CO2 and O2 balanced in the atmosphere; decomposition recycles nutrients and forms humus
Explanation
The diagram must show photosynthesis, feeding, respiration, decay and burning with arrows.