👉 Perioecians are a group of organisms that were once part of the Earth's atmosphere. This refers to the period in which gases like nitrogen and oxygen could exist in the atmosphere, but their concentrations became too high due to human activities such as burning fossil fuels, deforestation, and industrial processes. During this time, these gases released into the air would have been very stable, with no harmful effects on living organisms. However, over time, these gases began to accumulate in our atmosphere, leading
