Phylogenetic tree is a hypothesis about the evolutionary relationships among organisms
based on available anatomical and/or molecular data.
- It helps to show which species are more related to the other
DNA sequences of 2 closely related taxa show fewer differences as mutation rates relatively
constant and recently diverging species have less time to accumulate differences.
Sister groups Groups that are more closely related to each other than either of them is to
any other group.
A monophyletic group consists of a common ancestor and all its descendants.
Monophyletic Describes groupings in which all members share a single common ancestor
not shared with any other species or group of species. Eg: tetrapods and amphibians
Paraphyletic Describes groupings that include some, but not all, the descendants of a
common ancestor.
group “reptiles” excludes birds, although they share a common ancestor with the included
animals
Polyphyletic Describes groupings that do not include the last common ancestor of all
members.
Many features of skeletal anatomy and DNA sequence strongly support the placement of
birds as a sister group to the crocodiles and alligators.
