Question

1. which processes decrease the amount of carbon dioxide in the air?

Explanation:

Photosynthesis is a key process where plants (and some other organisms) use carbon dioxide, water, and sunlight to produce glucose and oxygen. During this process, carbon dioxide from the air is taken in by plants, thus reducing its amount in the atmosphere. Additionally, processes like carbon sequestration (e.g., in oceans where marine organisms use carbon dioxide to build shells, and over time these can be stored in sediment) also decrease atmospheric carbon dioxide. But the most well - known and fundamental biological process for reducing atmospheric $CO_2$ is photosynthesis.

Answer:

One main process that decreases the amount of carbon dioxide in the air is photosynthesis (carried out by plants, algae, and some bacteria, where they take in $\boldsymbol{CO_2}$ and convert it into organic matter and release oxygen). Other processes include carbon sequestration in oceans (where marine organisms incorporate carbon dioxide into their shells or tissues, and over geological time scales, this carbon can be stored in ocean sediments).