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If we're talking about single-celled organisms, it's quite possible that there are hundreds of "kingdoms" living among us. The trend to abandon the Linnaean cla

by lake99 8y ago

If we're talking about single-celled organisms, it's quite possible that there are hundreds of "kingdoms" living among us. The trend to abandon the Linnaean classificaton is quite prominent among those analyzing macroscopic organisms. But among those working with microscopic organisms, I've come across some of them abandoning the tree of life itself. My mind was blown when I watched the discussion between Dawkins and Venter. https://en.wikipedia.org/wiki/Kingdom_(biology)#Summary https://en.wikipedia.org/wiki/Kingdom_(biology)#Summary https://evolutionnews.org/2011/03/venter_vs_dawkins_on_the_tree_/ https://evolutionnews.org/2011/03/venter_vs_dawkins_on_the_t...

gus_massa 8y ago
The last article is extremely misleading. It is true that there are variations of the genetic code. (Wikipedia says 32, including the usual genetic code that we have. https://en.wikipedia.org/wiki/List_of_genetic_codes https://en.wikipedia.org/wiki/List_of_genetic_codes ) But the variations are minor, each has only a few changes from the most used code. For example mitochondria (that are also "we") have only 4 changes out of 64 https://en.wikipedia.org/wiki/Vertebrate_mitochondrial_code https://en.wikipedia.org/wiki/Vertebrate_mitochondrial_code . So the easiest explanation is that the genetic code evolved from a genetic code ancestor. Moreover, our genetic code is probably not the original code. IIRC the guess is that initially it has only 16 slots. These slots are visible as some big squares in the curren table, but some of these slots are divided now. Most of the time a change in the genetic code is catastrophic, so it's not easy to change it. But it may be possible if it changes one aminoacidic by a similar one, or if you are extremely lucky. In the table all the changes are in mitochondria/bacteria/archaea, not in animals or plants. Since they are small, they have bigger numbers and faster generations, so they have a bigger chance of a lucky random mutation. In particular, 12 of the 32 genetic codes in the list are variations in mitochondrial code. All the mitocondria are very similar. The incorporation of mitocondrial was a very strange lucky event. Nobody think that the 12 variants of mitochondria appear independently, each one in its own tree of life, and were absorbed later independently.
- lake99 8y ago
  I don't like the "gotcha, Dawkins" stance of the article, but apart from that, it looks like they were doing their best to fill in the gaps that Venter left. If memory serves me right, this discussion panel met shortly after Venter's group announced the creation of a life form with a completely synthetic genome. Venter had adequately proven his credentials by that point, and so the panel deferred to his expertise. Given that the likes of Dawkins could not follow along, Venter certainly did a poor job of communicating the ideas.

by lake99 8y ago

gus_massa 8y ago

The last article is extremely misleading. It is true that there are variations of the genetic code. (Wikipedia says 32, including the usual genetic code that we have. https://en.wikipedia.org/wiki/List_of_genetic_codes https://en.wikipedia.org/wiki/List_of_genetic_codes ) But the variations are minor, each has only a few changes from the most used code. For example mitochondria (that are also "we") have only 4 changes out of 64 https://en.wikipedia.org/wiki/Vertebrate_mitochondrial_code https://en.wikipedia.org/wiki/Vertebrate_mitochondrial_code . So the easiest explanation is that the genetic code evolved from a genetic code ancestor. Moreover, our genetic code is probably not the original code. IIRC the guess is that initially it has only 16 slots. These slots are visible as some big squares in the curren table, but some of these slots are divided now. Most of the time a change in the genetic code is catastrophic, so it's not easy to change it. But it may be possible if it changes one aminoacidic by a similar one, or if you are extremely lucky. In the table all the changes are in mitochondria/bacteria/archaea, not in animals or plants. Since they are small, they have bigger numbers and faster generations, so they have a bigger chance of a lucky random mutation. In particular, 12 of the 32 genetic codes in the list are variations in mitochondrial code. All the mitocondria are very similar. The incorporation of mitocondrial was a very strange lucky event. Nobody think that the 12 variants of mitochondria appear independently, each one in its own tree of life, and were absorbed later independently.

lake99 8y ago
I don't like the "gotcha, Dawkins" stance of the article, but apart from that, it looks like they were doing their best to fill in the gaps that Venter left. If memory serves me right, this discussion panel met shortly after Venter's group announced the creation of a life form with a completely synthetic genome. Venter had adequately proven his credentials by that point, and so the panel deferred to his expertise. Given that the likes of Dawkins could not follow along, Venter certainly did a poor job of communicating the ideas.