Iodine is the most primitive and abundant electron-rich essential element in the diet of marine and terrestrial organisms, and as iodide acts as an electron donor and has this ancestral antioxidant function in all iodide-concentrating cells from primitive marine algae to more recent terrestrial vertebrates.
32.
Although they are comparatively recent in the history of life ( the first terrestrial organisms appeared in the Silurian period, about 425 million years ago ) and occupy a much smaller portion of Earth's surface than marine ecosystems, terrestrial ecosystems have been a major site of adaptive radiation of both plants and animals.
33.
However, given Ir's low cosmic abundance, several orders of magnitude below V, Fe, and Cu ( which are actually used by terrestrial organisms ) and Mn and Co ( which would also work, but AFAIK are unattested in terrestrial organisms ), it seems rather unlikely that this compound is used in any alien species'blood . talk ) 03 : 18, 11 December 2014 ( UTC)
34.
However, given Ir's low cosmic abundance, several orders of magnitude below V, Fe, and Cu ( which are actually used by terrestrial organisms ) and Mn and Co ( which would also work, but AFAIK are unattested in terrestrial organisms ), it seems rather unlikely that this compound is used in any alien species'blood . talk ) 03 : 18, 11 December 2014 ( UTC)
