Final answer:
Oxygen is produced by plants during photosynthesis, where water and carbon dioxide are converted to glucose and oxygen with the help of sunlight and chlorophyll. The oxygen is then released into the atmosphere through the plants' stomata.
Step-by-step explanation:
The oxygen given off by plants is produced during the process of photosynthesis in the chloroplasts.
Photosynthesis is a critical process carried out by plants, releasing oxygen as a byproduct. In the presence of sunlight, plants use chlorophyll to convert water (H₂O) and carbon dioxide (CO₂) into glucose and free oxygen (O₂). The oxygen is released through the plant's stomata into the atmosphere. This process is not only vital for the survival of plants but also for sustaining animal life and maintaining atmospheric balance.
The initial emergence and evolution of photosynthetic organisms were essential in enriching Earth's atmosphere with oxygen, which subsequently allowed for the development of more complex life forms that depend on it for respiration. Through photosynthesis, plants and certain microbes convert the sun's energy into a form usable by other life forms, playing the role of primary producers in ecological systems.