Sunlight doesn’t actually give off oxygen. Light is energy. Oxygen is a kind of matter (stuff that takes up space and has mass).

I think I understand why you’re asking, though. In photosynthesis, plants take in water and carbon dioxide and make sugar and oxygen. The energy to do this work comes from light. The oxygen comes from the water molecules. It’s sort of like putting ingredients together, then baking them into cookies. The cookies come from the ingredients, but the heat energy is needed to make the ingredients into cookies. Do you think it’s possible to have an ecosystem without plants?

You might want to study botany—the science of plants.

Sunlight doesn’t “give off” oxygen but is essential for oxygen to be produced by plants. Plants give off oxygen during photosynthesis using the energy from sunlight. Plants convert carbon dioxide and water into sugar and oxygen using the energy harnessed from light.

Sunlight does not give off oxygen. Plants give off oxygen. Plants do this because they are taking the carbon out of carbon dioxide gas and are left with the oxygen left over as a byproduct. In order to avoid poisoning themselves with extra oxygen, they give it off. Plants get the energy to do this from sunlight, but sunlight itself does not release oxygen.