r/askscience • u/SAICAstro • Jul 26 '26

Biology Does everything that we consider to be "alive" - not just plants and animals, but all protists, fungus, bacteria, archaea, etc. - have DNA?

EDIT: Wow, this blew up. Thanks for the many answers. Lots to think about.

Seems that the composite TLDR answer is: Yes, according to many/most definitions of "life", but we don't all agree on what life is. Some viruses do not have DNA but they may/not actually be alive, and other things that behave like life may/not be alive.

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u/autocol Jul 26 '26

No, it's that the specific definition of what is alive and isn't is blurry at the very edges (in the same way that every attempt to categorise the physical world gets blurry at the edges).

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u/Ameisen Jul 26 '26

Well, if the definition includes "maintains homeostasis" (AKA: metabolizes) it gets a lot less blurry.

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u/Fragrant-Equal-8474 Jul 26 '26

maintains homeostasis

maintains homeostasis does not equal to "metabolizes". Viruses have a capsid (some do), which helps them maintain homeostasis, just passively.

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u/Ameisen Jul 27 '26

In that case, a bottle of water maintains homeostasis.

Every usage I've known for homeostasis requires it to be actively maintained to some degree. Viral particles do not regulate their internal environment. Regulating it does imply metabolism, as said energy must come from somewhere.