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an allotroph is an element that exists in two different forms but in the same phase. Example) oxygen gas (O2) and ozone gas (O3) The current definition refers to an autotroph - that is an organism that can make its own food. Example) a plant or photosynthetic bacteria

No, an autotroph manufactures its food from inorganic components. An allotroph (or heterotroph) takes in food that was made by other organisms. --EncycloPetey 00:23, 20 January 2009 (UTC)
You are essentially confusing two different terms for different concepts.
The correct chemical term is allotrope (where -trope denotes `(one of several possible different) forms'; OED states this is derived from (classical) Greek τρόπος (turn, way, manner, style) and τροπῄ (the act of turning, solstice)).
The biological term allotroph may or may not exist in English; it is not to be found in OED; but if it does exist with the sense suggested in our entry, like heterotroph it should be derived from Hellenistic Greek τροφικός, derived from (classical) Greek τροφῄ, nourishment. Under the entry for allotrophic, OED notes that this is sometimes (but rarely) used in the chemical sense, probably as a mistake for allotropic; while the biological sense, corresponding to the one given in our entry, is stated to be derived from the German word allotroph.
Now, if the word allotroph indeed is used in (scientific biological) German, it is not unlikely that it can be found in (scientific biological) English, too. However, this should be independently verified; where the former en-wp substub article and its various mirrirs and copies do not form part of the verification.
The German biological sense, indirectly attested in OED, anyhow should be given in this entry, I suppose; but preferably with a more direct confirmation.
As for the chemical sense, I suppose that this might be given as a misspelling of or mistake for allotrope. However, I do not know how en-wikt customarily treats such word forms sporadically appearing due to mistakes or misprints. JoergenB (talk) 14:49, 3 December 2014 (UTC)