The origin of oxygen (and other large elements) is from supernovae.
On the smaller scale, the vast majority of our oxygen comes from ocean plants, from tiny algae to giant kelp. The atmospheric oxygen comes from the decomposition of water and carbon dioxide by organisms that use photosynthesis to make useful molecules in combination with the energy from sun light.
Oxygen makes up about 21% of Earth's lower atmosphere by volume.
The approximate percent of oxygen in Earth's lower atmosphere is around 20.95% by volume.
The approximate percentage of oxygen in Earth's lower atmosphere is around 21% by volume.
Earths atmosphere is rich in Oxygen, some 21% of the air is Oxygen. There is oxygen on other planets, but the percentage comes nowhere close to this. The percentage of Oxygen in earths atmosphere is thought to have been much higher in the past, before animals were about, but after the arrival of plants.
The two most abundant gases in Earth's atmosphere are nitrogen (about 78%) and oxygen (about 21%).
The earths atmosphere is made up of 78% nitrogen and 21% oxygen
97%
no
Oxygen gas
Free oxygen
Plants
oxygen
Plants
Nitrogen and oxygen,
no
mostly nitrogen with 21% oxygen
photosynthsis