It's not only the study of human population, but the populations of non-human species, including viruses like influenza, the bacteria in your gut, plants that you eat, animals that you enjoy or that provide you with meat.
它不仅仅研究人类的数量,还有那些非人类物种的数量,包括像流感这样的病毒,你肠道里的细菌,你吃的植物,供你欣赏或食用的动物。