Assessment and Qualifications Alliance (AQA) AS Biology Practice Exam 2025 - Free AS Biology Practice Questions and Study Guide

Ultraviolet light is classified as a mutagenic agent because it has enough energy to cause changes in the DNA structure of living organisms. Specifically, UV light can lead to the formation of pyrimidine dimers, where two adjacent thymine bases bond together inappropriately. This causes errors during DNA replication, which can ultimately result in mutations. Mutations can disrupt normal cellular functions and lead to various consequences, including the development of cancer.

In contrast, low energy radiation and non-ionizing radiation typically do not have sufficient energy to directly damage DNA or induce mutations in the same manner as ultraviolet light. Carbon dioxide, while it is a significant compound in biological systems, does not have mutagenic properties and does not directly interact with DNA to cause mutations. Thus, ultraviolet light stands out as a clear example of a mutagenic agent among the options provided.