Question

What do you know about the presence of oxygen on earth?

Answer 1

Hint: Oxygen is a chemical element with the atomic number $$8$$ and the symbol O. It is a highly reactive nonmetal and an oxidising agent that readily forms oxides with most elements and other compounds. It belongs to the chalcogen group in the periodic table. By mass, oxygen is the third most abundant element in the universe, after hydrogen and helium.

Complete answer:
Two atoms of the element join together at normal temperature and pressure to form dioxygen, a colourless and odourless diatomic gas. Oxygen, in the form of oxides, makes up almost half of the Earth's crust.
Many major classes of organic molecules in living organisms, such as proteins, nucleic acids, carbohydrates, and fats, contain oxygen atoms, as do the major constituent inorganic compounds of animal shells, teeth, and bone.
Dioxygen provides the energy produced in combustion and aerobic cellular respiration, and many major classes of organic molecules in living organisms, such as proteins, nucleic acids, carbohydrates, and fats, contain oxygen atoms.
The majority of the mass of living organisms is oxygen, which is a component of water, which is the primary component of all lifeforms. Photosynthesis, which uses the energy of sunlight to create oxygen from water and carbon dioxide, replenishes oxygen in the Earth's atmosphere on a continuous basis.

Earth crust	$45-50\mathrm{\%}$
Water	$88-90\mathrm{\%}$
Air	$21\mathrm{\%}$
Plants	$60-70\mathrm{\%}$
Animals	$60-70\mathrm{\%}$

We can observe from the table that the amount of oxygen in nature is very high.

Note:
Oxygen is too chemically reactive to remain a free element in air unless it is constantly replenished by living organisms' photosynthetic activity. Production of steel, plastics, and textiles, brazing, welding, and cutting of steel and other metals, rocket propellant, oxygen therapy, and life support systems in aircraft, ships, spaceflight, and diving are all examples of common uses of oxygen.