Developing the atmosphere - AQAHow oxygen increased
The early atmosphere was mainly carbon dioxide and water vapour. Water vapour condensed to form the oceans. Photosynthesis caused the amount of carbon dioxide to decrease and oxygen to increase.
Plants make their own food by photosynthesisA chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.. In this process, carbon dioxide is reacted with water to produce glucose, with oxygen as a by-productSomething that is produced as a waste product.:
carbon dioxide + water 鈫 glucose + oxygen
6CO2(g) + 6H2O(l) 鈫 C6H12O6(aq) + 6O2(g)
Scientists think that algaeA group of organisms that photosynthesise but lack the complex range of cell types and organs found in land plants. Most algae are aquatic. All have chloroplasts. first evolved approximately 2.7 billion years ago, and soon after this
oxygen began to exist in the atmosphere. Photosynthesis by primitive plants and algae released oxygen, which gradually built up in the atmosphere. Eventually, the amount of oxygen present in the atmosphere enabled animals to evolve.