The ability to detect chemicals in the environment serves many functions, a crucial one being the detection of food, a function that first arose in single-celled organisms (bacteria) living in the oceans during the early days of life on Earth.
检测环境中化学物质的能力对生物有着许多用处，其中一个十分重要的用处即是寻找食物，这一功能首先出现在地球生命发展初期生活在海洋中的单细胞生物（细菌）上。