Читать книгу Principles of Microbial Diversity - James W. Brown - Страница 62

The scale typically is either time or evolutionary distance. Trees with a time scale are based on some form of physical data, such as a fossil record, that provide dating information. If the scale is time, all modern organisms should obviously be shown at the same part of the scale (the present). More often, the scale is evolutionary distance, i.e., some measure of change in the organisms (or molecules). Because the extent of divergence is usually different in various parts of the tree, this is depicted by the lengths of the branches and a scale bar.