1. Photosynthesis: This process is carried out by plants, algae, and some bacteria. They use sunlight, water, and carbon dioxide to produce their own food (sugars) and release oxygen as a byproduct. This removes carbon dioxide from the atmosphere and incorporates it into organic molecules.

2. Cellular Respiration: This process is carried out by all living organisms. They break down organic molecules (sugars) in the presence of oxygen to release energy for their life processes. This releases carbon dioxide back into the atmosphere.

These two processes are essentially the opposite of each other, and they work in balance to keep the carbon cycle going.