Living things need an atmosphere that provides a balance of gases essential for their survival, primarily oxygen and carbon dioxide.

• Oxygen (about 21% of Earth's atmosphere) is crucial for most animals and many microorganisms because it is required for cellular respiration, the process that produces energy for vital functions

• Carbon dioxide is essential for plants, as they use it in photosynthesis to produce glucose and release oxygen, maintaining the atmospheric balance necessary for life

• Besides these gases, the atmosphere also contains nitrogen (about 78%), which is inert but important for many biological processes, and trace gases including argon

• The atmosphere acts as a protective blanket that regulates temperature, shields living organisms from harmful ultraviolet radiation via the ozone layer, and supports the water cycle through precipitation, all of which are vital for sustaining life

• The right temperature range maintained by the atmosphere is also critical, as metabolic and physiological processes in living organisms depend on suitable thermal conditions

In summary, living things need an atmosphere that contains sufficient oxygen for respiration, carbon dioxide for photosynthesis, and other gases that support life processes, while also providing protection and temperature regulation to create a habitable environment