selection pressure

This term is a technical expression used primarily in evolutionary biology and ecology. It describes the specific environmental constraints—such as predation, climate change, or resource scarcity—that filter a population, allowing only those with favorable adaptations to survive and pass on their genes.

While the word "pressure" often implies a physical force or psychological stress in general English, in this scientific context, it refers to a statistical or biological bias toward certain phenotypes. It is almost always used in a neutral, descriptive sense to explain the mechanism of natural selection rather than to imply a conscious effort or a negative burden.