What impact does the ozone layer have on Earth?

The ozone layer plays a crucial role in protecting living organisms from harmful solar radiation, particularly ultraviolet (UV) radiation. This layer of ozone (O3) is found in the Earth's stratosphere and serves as a shield against the sun's most damaging rays. Without the ozone layer, increased levels of UV radiation would penetrate the atmosphere, leading to a higher incidence of skin cancers, cataracts, and other negative health effects in humans, as well as detrimental impacts on ecosystems, including damage to phytoplankton and other marine organisms crucial for food webs.

The other choices, while they touch upon important aspects of Earth's systems, do not accurately represent the primary function of the ozone layer. For instance, the moderation of ocean temperatures, filtering of freshwater, and aiding in gaseous exchange are not related to the specific protective capacity of the ozone layer against solar radiation. Therefore, the impact of the ozone layer in safeguarding life from harmful UV rays is what makes this answer the most appropriate choice.