Identify the names of the processes in the carbon cycle described below:

(i) The biochemical process by which living organisms break down organic molecules, releasing carbon dioxide back into the atmosphere or water.

(ii) The geological process by which dead organic matter is compressed under high pressure and temperature over millions of years to form coal, crude oil, and natural gas.

A marine biologist is designing a sealed aquatic mesocosm to study closed biospheres. They fill a glass chamber with sterilized artificial seawater containing essential dissolved mineral ions but no living microbes, and introduce a population of photosynthetic green microalgae.

(i) Explain why the microalgae will eventually stop reproducing and die off if no other organisms are added to the mesocosm.

(ii) Explain how introducing heterotrophic marine bacteria (decomposers) to the mesocosm enables the microalgae and the bacteria to supply each other with the gases they need to survive in the sealed chamber.