Key Stage 3 (KS3) General Knowledge Practice Test 2026 - Free KS3 Practice Questions and Study Guide

During photosynthesis, trees and other green plants utilize sunlight to convert carbon dioxide and water into glucose and oxygen. The process involves chlorophyll, the green pigment in leaves that captures light energy. As a byproduct of this conversion, oxygen is released into the atmosphere. This release of oxygen is crucial for life on Earth, as it provides the essential gas that many living organisms, including humans, need to breathe.

The other gases mentioned do not play a role in this specific process of photosynthesis. While carbon dioxide is consumed during the process, nitrogen is largely inert in this context, and hydrogen does not directly relate to the output of gases from photosynthesis. Understanding the role of oxygen in supporting life highlights the importance of trees and plants in our ecosystem.