7.9 Phylogeny

• Phylogenetic trees


  Branch diagram showing the evolutionary relationship amongst species
• Cladograms


  Diagram used to show evolutionary relationships
• How phylogenetic trees and cladograms are used

  1. Infer evolutionary relationships

  2. Construct phylogenetic trees and cladograms
• Shared derived characteristic

  Trait present in more than one lineage that indicates common ancestry
• Shared derived characteristics are informative for constructing phylogenetic trees and cladograms
• Outgroup is a closely related group used to show how the main group fits in the evolutionary tree of life
• Phylogenetic trees and cladograms


  Can indicate speciation has occurred
• Root


  Common ancestor of all species on the phylogenetic tree or cladogram
• Phylogenetic trees and cladograms can be drawn with diagonal, vertical or horizontal lines, and the orientation can be vertical or horizontal
• Nodes on phylogenetic trees and cladograms can be rotated
• Derived character

  Trait in a recent species having evolved from an ancestral trait
• Molecular data typically provides more accurate and reliable evidence than morphological traits for constructing phylogenetic trees and cladograms
• Phylogenetic tree 1


  • Represents the relationship of whales to six other mammals
• Phylogenetic tree 2


  • Constructed based on new evidence including the camel being an outgroup and the whale and hippo having a similar pattern of DNA sequences
• Phylogenetic trees and cladograms represent hypotheses that are constantly being revised based on evidence
• The polar bear has 7 amino acid differences compared to the black bear, and the black bear and brown bear only have 1 amino acid difference
• The panda is the outgroup and is the least closely related to the other species