Oxygen in the Atmosphere
Chemistry: AQA GCSE Higher, topic 9.1.3
The Rise of Oxygen in the Earth's Atmosphere
Photosynthesis increased the atmospheric concentration of oxygen.
What is photosynthesis?
- Photosynthesis uses light energy to make glucose and oxygen.
- Glucose and oxygen are made from carbon dioxide and water.
Photosynthetic organisms
- Algae were the first photosynthetic organisms to evolve.
- Algae evolved about 2.5-2.7 billion years ago.
Plant evolution
- Photosynthesising plants then began to evolve over the next billion years.
- Plant evolution led to a growing rate of oxygen accumulating in the atmosphere.
Evolution of complex organisms
- More complex life forms, such as animals, began to evolve.
- Evolution happened once a threshold concentration of oxygen was reached.
Test yourself on Oxygen in the Atmosphere
Why were animals unable to evolve until millions of years after algae first appeared?
What is needed for photosynthesis to take place?
What is true of photosynthesis and its effects on life on Earth?
Which organisms were responsible for the earliest increases in atmospheric oxygen, before photosynthesising plants evolved?
What most likely caused the rate of oxygen build-up in the atmosphere to increase after photosynthesising plants evolved?