Evolutionary ChronometerComments
siblingsBinomial NomenclatureCaenorhabditis elegansColiform BacteriaDarwinian EvolutionDeuterostomesDrosophila melanogasterEchinodermsEvolutionary agentsEvolutionary ConstraintsPhylogeneticsPhylum AnnelidaPhylum CnidariaPhylum Platyhelminthes and NemerteaPhylum PoriferaReconstructing PhylogeniesTaxonomic Units

Evolutionary Chronometer

An evolutionary chronometer (or ED) is a nucleotide or amino acid sequence that is similar between two organisms and can be used to measure their evolutionary separation. Evolutionary distance (or how many ancestors ago the two species diverge) is proportional to how many differences there are between the nucleotide or amino acid sequences. Thus, an evolutionary chronometer (also denoted ED) essentially represents the number of changes between two sequences. DNA segments encoding ribosomes, ATPases and DNA Polymerases are all good evolutionary chronometers because they are universally conserved for the most part.