WAEC Biology 2015 Theory — Question 15

Model answer

The carbon cycle diagram shows: atmospheric carbon (IV) oxide (CO₂) at the top, linked by arrows labelled 'photosynthesis' down to green plants, and by 'respiration' up from plants and animals back to the atmosphere. CO₂ dissolves in river/sea water and is used by aquatic plants. Plants and animals form complex organic compounds in the plant/animal body; upon death and decay (through decomposers/microbial decomposition), large bodies of carbon are returned to the soil, released as CO₂ through decomposition, or converted over long periods into fossil fuels/industrial processes, which release CO₂ back into the atmosphere upon combustion, completing the cycle.