What is an organism?

An organism is defined as a single living thing that has the ability to carry out life processes such as growth, reproduction, and responding to stimuli. This definition encompasses a wide variety of life forms, including animals, plants, fungi, and microorganisms. Each organism is comprised of one or more cells, which perform the functions necessary for life, but the key characteristic that distinguishes an organism is its status as a distinct living entity capable of maintaining homeostasis and interacting with its environment.

Choosing the option that labels an organism as a single living thing captures the essence of what an organism is, encompassing both unicellular forms, like bacteria, and multicellular forms, like humans and trees. Understanding this definition is crucial in biology, as it lays the foundation for studying more complex concepts related to life, such as ecosystems and biodiversity.