Life is a characteristic distinguishing physical entities having signaling and self-sustaining processes from those that do not, either because such functions have ceased (death), or because they lack such functions and are classified as inanimate.

Life is a characteristic distinguishing physical entities having signaling and self-sustaining processes from those that do not, either because such functions have ceased (death), or because they lack such functions and are classified as inanimate. Biology is a science concerned with the study of life.

The smallest contiguous unit of life is called an organism. Organisms are composed of one, or more, cells, undergo metabolism, maintain homeostasis, can grow, respond to stimuli, reproduce and, through evolution, adapt to their environment in successive generations. A diverse array of living organisms can be found in the biosphere of Earth, and the properties common to these organisms—plants, animals, fungi, protists, archaea, and bacteria — are a carbon - and water-based cellular form with complex organization and heritable genetic information.

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