In this lesson you explored this essential question:

  • How does the relationship between gas exchange in photosynthesis and cellular respiration influence the composition of the atmosphere?

Two biological processes â€” photosynthesis and cellular —respiration  are hugely important to the biosphere. These processes have, over a billion years, established the balance of oxygen and carbon dioxide that all life on Earth depends on. It is not easy, yet despite knowing how difficult it is to maintain a balance, people continue activities that alter the atmosphere in a variety of ways which scientists propose is causing global warming.

Module Glossary

anoxic: lacking free oxygen

ecological footprint: an analysis of human consumption of natural resources compared to the ability of Earth to recreate them

An ecological footprint gives an estimate of the area in hectares that is required for a human to live based on his or her lifestyle. Most North American lifestyles are not currently sustainable, according to the analyses.

stromatolites: sedimentary rock in oceans built from fossilized micro-organisms, such as bacteria

sustainable: capable of being continued with minimal long-term effects on the environment


Complete Unit A: Section 3 Assignment now.