7.9 Phylogeny

Life continues to evolve within a changing environment. Describe the types of evidence that can be used to infer an evolutionary relationship. Phylogenetic trees and cladograms both show relationships between lineages, but phylogenetic trees show the amount of change over time calibrated by fossils or a molecular clock. Traits that are either gained or lost during evolution can be used to construct phylogenetic trees and cladograms-- Shared characters are present in more than one lineage. Shared, derived characters indicate common ancestry and are informative for the construction of phylogenetic trees and cladograms. The out-group represents the lineage that is at least closely related to the remainder of the organisms in the phylogenetic tree or cladogram. Molecular data typically provide more accurate and reliable evidence than morphological traits in the construction of phylogenetic trees or cladograms. Explain how a phylogenetic tree and/or cladogram can be used to infer evolutionary relatedness. Phylogenetic trees and cladograms can be used to illustrate speciation that has occurred. The nodes on a tree represent the most recent common ancestor of any two groups or lineages. Phylogenetic trees and cladograms can be constructed from morphological similarities of living or fossil species and from DNA and protein sequence similarities. Phylogenetic trees and cladograms represent hypotheses and are constantly being revised based on evidence.

phylogeny

history of evolution, shows lines of ancestry and relationships

phylogenetic trees and cladograms

used to demonstrate evolutionary relationships

• phylogenetic trees indicate approximate time of evolutionary events

• uses estimates from morphological and molecular (more accurate) data

• represent hypotheses, constantly being revised

clades

related group, shared characteristics and evidence of common anscestry

common ancestry

nodes and root

out-group

least closely related member of the tree