10.3 phylogeny

what is phylogeny

• the name given to the evolutionary relationships between organisms

• the study of the evolutionary history of groups of organisms is known as phylogenics

phylogenic trees

• a diagram used to represent the evolutionary relationship between organisms

• they are branched diagrams which show that a species have evolved form a common ancestor

advantages of phylogenic classification

• phylogeny produces a continuous tree whereas classification requires a discrete taxonomical groups. Scientists are not forced to put specific organisms into groups where they do not quite fit

• confirms classification groups are correct and causes them to be changed

• the hierarchical nature of linnaean classification can be misleading as it implies different groups within the same rank are equivalent

interpreting phylogenetic trees

• the tips of the phylogenetic tree represent groups of descendant organisms

• the nodes on the trees represent the common ancestors of those descendants

• two descendants split form the same node are called sister groups

• the closer the branches of the tree are, the closer the evolutionary relationship