Question

Q. How is oxygen replaced in nature?

Answer 1

Oxygen cycle, circulation of oxygen in various forms through nature. Free in the air and dissolved in water, oxygen is second only to nitrogen in abundance among uncombined elements in the atmosphere. Plants and animals use oxygen to respire and return it to the air and water as carbon dioxide (CO2).

Answer 2

Name two process in which oxygen is used from atmosphere?

Photosynthesis:- by plants....

Respiration:- by humans