Final answer:
The atmospheric layer where gases do not maintain a uniform composition is called the troposphere. It's the lowest layer of Earth's atmosphere, with a variable mixture of gases primarily due to weather events and biological activities.
Step-by-step explanation:
The atmospheric layer in which gases do not maintain a uniform composition is the troposphere. The troposphere is the lowest layer of Earth's atmosphere and is where most of the planet's weather processes occur. It is characterised by a decreasing temperature with altitude and a mixing of gases due to the weather phenomena and biological activities happening within it. In contrast to the stratosphere, mesosphere and thermosphere, where the composition of gases is more stratified and stable, the troposphere has a variable mixture of gases such as nitrogen, oxygen, argon, carbon dioxide, water vapor, and numerous other compounds.