Gaseous cycle

Lesson 10: Bio-geo-chemical cycles

Carbon cycle

Carbon is a building block of both plant and animal tissues. In the atmosphere, carbon occurs as carbon dioxide. In the presence of sunlight, plants take up carbon dioxide from the atmosphere through their leaves. The plants combine carbon
dioxide with water, which is absorbed by their roots from the soil. In the presence of sun light they are able to form carbohydrates that contain carbon,
for their growth and development. This process is known as photosynthesis. In this process, plants release oxygen into the atmosphere on which animals depend for their respiration. Herbivores feed on plant material, which is used by them for energy and growth. Both plants and animals release carbon dioxide during respiration. They also return fixed carbon to the soil in the waste they excrete. When plants and animals die, they return their carbon to the soil. These processes complete the carbon cycle.

Carbon returns to the physical environment in a number of ways. Both plants and animals respire, so they release CO2 during respiration. Luckily for animals, plants just happen to consume more CO2 through photosynthesis than they can produce. Another route of CO2 back to the physical environment occurs through the death of plants and animals. When organisms die, decomposers consume their bodies. In the process, some of the carbon returns to the physical environment by way of fossilization. Some of it remains in the biological environment as other organisms eat the decomposers. But by far, most of the carbon returns to the physical environment through the respiration of CO2.

Last modified: Thursday, 29 December 2011, 7:46 AM