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I imagine it's similar to how viruses are not considered to be alive, since they cannot reproduce without a host cell? But I have never been a fan of that argu

by ssalka 2y ago

I imagine it's similar to how viruses are not considered to be alive, since they cannot reproduce without a host cell? But I have never been a fan of that argument either, both seem alive to me.

georgeecollins 2y ago
I think the idea here is that mitochondria developed independent of cells and later lived exclusively inside of them. In other words, they reproduced without cells. I am not sure, please correct me if I am wrong.
- semperdark 2y ago
  You're not wrong. But over the enormous amount of time since, the "duplicate" organelles and systems needed for independent living were steadily carved out of mitochondria. While they do have their own DNA and replication process, the DNA is basically limited to specific things they need to perform their energy-generation functions and the replication happens when triggered by host cell replication. It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
- dekhn 2y ago
  No, the predecessors of mitochondria were also cells and they reproduced through cellular division.
adastra22 2y ago
I don't know of any definition of "alive" that can survive application of a reductive understanding of biology that doesn't either count viruses as being "alive," or decide that nothing is alive. The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.
larkost 2y ago
Outside of a host cell viruses do not fit any of the definitions of life: - they do not seek or consume sources of nutrients or energy - they do not have a metabolism - they do not grow In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect. To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.

by ssalka 2y ago

I imagine it's similar to how viruses are not considered to be alive, since they cannot reproduce without a host cell? But I have never been a fan of that argument either, both seem alive to me.

georgeecollins 2y ago

I think the idea here is that mitochondria developed independent of cells and later lived exclusively inside of them. In other words, they reproduced without cells. I am not sure, please correct me if I am wrong.

semperdark 2y ago
You're not wrong. But over the enormous amount of time since, the "duplicate" organelles and systems needed for independent living were steadily carved out of mitochondria. While they do have their own DNA and replication process, the DNA is basically limited to specific things they need to perform their energy-generation functions and the replication happens when triggered by host cell replication. It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
dekhn 2y ago
No, the predecessors of mitochondria were also cells and they reproduced through cellular division.

adastra22 2y ago

I don't know of any definition of "alive" that can survive application of a reductive understanding of biology that doesn't either count viruses as being "alive," or decide that nothing is alive. The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.

larkost 2y ago

Outside of a host cell viruses do not fit any of the definitions of life: - they do not seek or consume sources of nutrients or energy - they do not have a metabolism - they do not grow In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect. To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.