Food chains show the feeding relationships between living things. Pyramids of biomass reveal the mass of living material at each stage in a chain. The amount of material and energy decreases from one stage to the next. Carbon moves from the atmosphere into living species and back into the atmosphere in a cycle that is crucial to life on Earth.

Some of the substances released during decay are needed by plants for healthy growth. In a stable community of living things, processes that return substances to the environment (such as decay) are balanced by the processes that remove and use substances. In this way, the substances are continuously recycled.

Removing carbon dioxide from the atmosphere
Green plants and algae remove carbon dioxide from the atmosphere by photosynthesis. The carbon becomes part of complex molecules such as proteins, fats and carbohydrates in the plants and algae.

rganisms return carbon dioxide to the atmosphere by respiration. It is not just animals that respire. Plants, algae and microorganisms do too.
Carbon dioxide is also released into the atmosphere when fossil fuels such as coal and oil, and wood, are burned.