Answer:
Cyanobacteria are early organisms that produced oxygen, increasing oxygen in early Earth's atmosphere. Animals produce carbon dioxide, increasing carbon dioxide in the atmosphere.
The burning of fossil fuels increase greenhouse gases in the atmosphere.
The most abundant gas released into the atmosphere from volcanic systems is water vapor.
Sulfur dioxide gas from volcanoes can lead to acid rain and air pollution.
Carbon dioxide produced by volcanoes adds to greenhouse gases in the atmosphere.