Final answer:
A complete and entire living thing is called an organism. Organisms can range from single-celled entities like bacteria to complex multicellular ones like animals and plants, all sharing the ability to carry out life processes, grow, and reproduce.
Step-by-step explanation:
Any complete and entire living thing is called an organism. Living organisms vary greatly in complexity and can be unicellular, like bacteria, or multicellular, like humans and other animals. All organisms share certain essential characteristics: they require energy to carry out life processes, are composed of cells, respond to their environment, grow, reproduce, and maintain a stable internal environment. This amazing diversity among organisms is the result of evolution, leading to various forms such as plants, animals, fungi, bacteria, and archaea.
A single cell is considered the smallest unit of a living organism, providing the basic building block for more complex life forms. It's incredible to imagine that every multicellular organism starts its life from a single cell that arises from the union of an ovum and a sperm.