▁The ▁pro k ary otes ▁( the ▁two ▁domains ▁of ▁b acter ia ▁and ▁arch ae a ) ▁and ▁certain ▁animals ▁such ▁as ▁b d ello id ▁rot if ers ▁have ▁the ▁ability ▁to ▁transfer ▁gen etic ▁information ▁between ▁un related ▁organ isms ▁through ▁horizontal ▁gene ▁transfer . ▁Re com bin ation , ▁gene ▁loss , ▁dup lication , ▁and ▁gene ▁creation ▁are ▁a ▁few ▁of ▁the ▁processes ▁by ▁which ▁gen es ▁can ▁be ▁transferred ▁within ▁and ▁between ▁b acter ial ▁and ▁arch ae al ▁species , ▁causing ▁variation ▁that ▁is ▁not ▁due ▁to ▁vertical ▁transfer . ▁There ▁is ▁emer ging ▁evidence ▁of ▁horizontal ▁gene ▁transfer ▁within ▁the ▁pro k ary otes ▁at ▁the ▁single ▁and ▁mult ic ell ▁level , ▁so ▁the ▁tree ▁of ▁life ▁does ▁not ▁explain ▁the ▁full ▁complexity ▁of ▁the ▁situation ▁in ▁the ▁pro k ary otes . ▁ ▁See ▁also ▁▁ ▁B acter ial ▁ph y la ▁ ▁Cl ad istics ▁ ▁Common ▁descent ▁ ▁Cor al ▁of ▁life ▁ ▁History ▁of ▁evolution ary ▁thought ▁ ▁Hol ism ▁ ▁Hor izontal ▁gene ▁transfer ▁ ▁Human ▁tim eline ▁ ▁Last ▁universal ▁common ▁ancest or ▁ ▁Mass ▁ext in ctions ▁ ▁Nature ▁tim eline ▁ ▁Ph y log en etic ▁tree ▁ ▁Sym bi ogen esis ▁ ▁Tree ▁of ▁Life ▁Web ▁Project ▁ ▁References ▁ ▁Further ▁reading ▁ ▁External ▁links ▁ ▁Tree ▁of ▁Life ▁Web ▁Project ▁- ▁explore ▁complete ▁ph y log en etic ▁tree ▁interact ively ▁ ▁Tree ▁of ▁Life ▁E volution ▁Link s ▁species ▁on ▁Earth ▁through ▁a