Quick answer: Living organisms generally have organized cells, use energy, maintain internal conditions, respond to their environment, and participate in reproduction and evolution.
What to know
Not every individual organism can reproduce, so biologists describe life using a cluster of properties rather than one flawless checklist.
Practical context
Viruses challenge simple definitions because they evolve but depend on host cells to reproduce.
Frequently asked question
Is fire alive because it grows?
No. Fire spreads and uses energy, but it lacks cells and inherited biological information in the way organisms possess it.
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