I discovered that immortals are not alive by biological standards

Going from what Integrated Principles of Zoology, 14th Edition, says (I save all my college textbooks), the qualities of life are:

• Chemical uniqueness: That is, living creatures are composed of complex macromolecules that are not seen in non-living entities.

• Complexity and hierarchial organization (most likely what your teacher summed up as 'cells.'): That is, their degree of organization goes beyond 'atoms and molecules', and into organelles, cells, populations, species, and the like.

• Reproduction: Speaks for itself, really.

• Possession of a genetic program: May not be DNA, but living organisms must be able to pass on traits to their kin.

• Metabolism: In order to continue themselves, they need to take in nutrients from the surrounding environment.

• Development: Organisms change over time, such growing in size, undergoing the stages of interphase, or going from a set of gametes to an egg to an embryo to an infant to an adult.

• Environmental interaction: Living organisms have the property of irritability; they respond to environmental stimuli.

• Movement: That is, not simple movements caused by external factors, but movements that arise from within the organisms themselves.

So, going from that, it seems the issue is more that your teacher is not fully versed in the subject s/he's teaching, or at least not the modern developments of it. I wouldn't say s/he's crazy, however.

edited 1st Feb '11 9:58:45 AM by Miijhal

OP: A Teacher of mine once gave that definition, and then proceeded to point out that mules are unable to reproduce, and therefore technically unable to evolve. His point was simply that "Life" is very hard to define without including things normaly considered non-life or excluding things considered alive.

edited 1st Feb '11 10:16:59 AM by uximata

"Development: Organisms change over time, such growing in size, undergoing the stages of interphase, or going from a set of gametes to an egg to an embryo to an infant to an adult."

That would exclude most immortals, but not Age Without Youth types. Or the ones who gradually look more and more inhuman.

edited 1st Feb '11 2:30:17 PM by Ettina

Wouldn't that depend on what you mean by change? An immortal might change their worldview, for instance.

^^At some point they developed from one stage to another. Unless they're like, a floating egg with a sperm still waltzing around inside. Furthermore, for them to heal wounds or retain knowledge, their cells would need to undergo change.

edited 1st Feb '11 3:17:02 PM by Miijhal

@Ettina: Uhm, yes, that was exactly my point. You can't apply evolution to an individual organism, because evolution isn't something that happens to an individual, it happens to a population.

As I recall, there are species out there that are effectively immortal, in that they do not have any kind of aging degeneration as mammals do, for instance. Lobsters are one such. They will live until some external factor kills them.