Lecture 2: Describing Microbial Diversity: the ... - MCD Biology

C. Indeed, the tree is a quantitative estimate – a metric - for that slippery concept, amount of evolution. The
“amount of biological diversity” (for any particular molecule) might be the summation of all unique line segment-
lengths in a comprehensive tree.
11.Some lessons from the Big Tree:
27
A. There was a single origin for terrestrial type of life -- all life forms are related.
B. Three “primary lines of evolutionary descent” -- ”Domains” -- “ur-kingdoms”: Eucarya (eucaryotes),
Bacteria, Archaea (originally called “archaebacteria”, but the name was changed when it became clear that
the things aren’t bacteria.)
1. Sometimes see referred to as “kingdoms,” but usage in this context is probably not a good idea -- too
historically loaded.
2. You can inject "time" into tree, but sequence change is not necessarily linear with time - indeed, probably it
usually isn't.