Which term describes any living thing?

The term that describes any living thing is "organism." An organism can be a single-celled entity like bacteria or a complex multicellular entity such as plants and animals. It represents the basic unit of life that exhibits the characteristics of life, including growth, reproduction, metabolism, and response to stimuli.

In contrast, species refers to a group of organisms capable of interbreeding and producing fertile offspring, which is a broader category than a single living entity. A community involves different populations of organisms interacting in a shared environment, while a population represents a group of individuals of the same species living within a specific area. Therefore, while these terms describe various levels of biological organization, "organism" is the most direct term for any individual living thing.