Question

gcse biology ecology & ecosystems high demand questions questionsheet 16 the diagram shows the carbon cycle. (a) in what form does carbon exist in the atmosphere? 1 (b) what process is represented by, (i) arrow 1? 1 (ii) arrow 2? 1 (iii) arrow 5? 1 (iv) arrow 6? 1

Explanation:

• (a) Carbon in the atmosphere is mainly in the form of carbon dioxide ($CO_2$).
• (b)(i) Arrow 1 represents photosynthesis. Plants take in carbon dioxide from the atmosphere and convert it into organic compounds (carbon in plants) using sunlight.
• (b)(ii) Arrow 2 represents respiration. Organisms (plants, herbivores, carnivores) release carbon dioxide back into the atmosphere as they break down organic compounds for energy.
• (b)(iii) Arrow 5 represents the formation of fossil fuels. Organic remains in the soil over a long period of time under high pressure and temperature are transformed into fuels like coal, oil, and gas.
• (b)(iv) Arrow 6 represents the combustion of fuels. When fuels are burned, carbon dioxide is released back into the atmosphere.

Answer:

(a) Carbon dioxide ($CO_2$)
(b)(i) Photosynthesis
(b)(ii) Respiration
(b)(iii) Formation of fossil fuels
(b)(iv) Combustion of fuels