The characteristics of life can be difficult to define, but there are several key features that are commonly used to describe living organisms. These characteristics are not necessarily exhaustive or mutually exclusive, and there may be exceptions or variations depending on the organism in question. Here are some of the most commonly cited characteristics of life:
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Order: Living things are organized at various levels, from cells to tissues to organs to organ systems to organisms to populations to ecosystems.
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Sensitivity or response to stimuli: Living things can detect and respond to changes in their environment, such as light, temperature, sound, or chemicals.
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Reproduction: Living things can produce offspring, either sexually or asexually.
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Adaptation: Living things can evolve over time to better suit their environment and increase their chances of survival.
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Growth and development: Living things can grow and change over time, from a single cell to a mature organism.
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Regulation: Living things can maintain internal stability, or homeostasis, by regulating their internal environment.
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Energy processing: Living things can obtain and use energy to carry out their life processes, such as metabolism, movement, and reproduction.
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Self-reproduction with variations: According to one analysis of 123 definitions of life, life can be defined as "self-reproduction with variations and natural selection".
Its worth noting that different sources may use slightly different terminology or group these characteristics in different ways. For example, some sources may include "metabolism" as a separate characteristic, while others may include it as part of "energy processing" or "regulation." Nonetheless, these characteristics provide a useful framework for understanding what makes something "alive."
