from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. of, or relating to organisms
from the GNU version of the Collaborative International Dictionary of English
- adj. of or pertaining to organism (definition 2).
from The Century Dictionary and Cyclopedia
- Of or pertaining to or produced by living organisms: as, organismal fermentation.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of or relating to or belonging to an organism (considered as a whole)
Sorry, no etymologies found.
Words like "latent evolutionary potential was realized", "realize preexisting evolutionary potential" and "a major innovation in organismal complexity — first the eukaryotic cell and later eukaryotic multicellularity" seem to have raised a few eye brows.
So what changes at the "Darwinian threshold" to make molecular homology a reliable indicator of common ancestry [organismal descent] above that point, but not below?
Put another way, how many organismal lineages carrying those characters crossed the Darwinian threshold?
No existing observations support such a claim, and given the massive global dominance of unicellular species over multicellular eukaryotes, both in terms of species richness and numbers of individuals, if there is an advantage of organismal complexity, one can only marvel at the inability of natural selection to promote it.
The universal phylogenetic tree, therefore, is not an organismal tree at its base but gradually becomes one as its peripheral branchings emerge.
I replied that when molecular homology is decoupled from organismal (vertical) descent, as Woese and others have done for universally-shared characters such as the genetic code, unexpected consequences follow for inferences about the branches of the Tree of Life.
This is a “Darwinian threshold” or “transition,” the point at which molecular homology now reliably indicates organismal, or vertical, descent:
Given that these lines of ancestry do not converge to a point, but pass through an interval of indeterminate width into a communal state, the set of ancestors of any eukaryote will not include a universally shared organismal member (usually referred to the literature as the last eukaryotic common ancestor, LECA).
There seemed no possibility of assessing the overall congruence of organismal and molecular trees, because microbial systematists had given up on the former and since the mid 1950s have been content with more practical schemes aimed at reliable species-level identification (38, 39).
If the molecular characters that define this domain allow phylogenetically reliable inferences to organismal common ancestry — that is, not to communally distributed (i.e., arising) traits, which are not diagnostic, but rather to vertical descent from unique (token) cells — then we need to know how many times those characters arose (came to be).
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