Topic 4: systematics and Phylogeny Flashcards

• what is Systematics

  the theory and practice of classifying organisms based on evolutionary history (phylogeny)
• what do phylogenies show

  show evolutionary relationships
• what are phylogenies inferred from?

  • morphological data
  • molecular data
• what is morphological data

  the size, shape, and presence or absence of different anatomical features
• what does morphological data apply to?

  both extant (living) species and extinct (fossils) species
• what does extant mean


  living
• what is molecular data

  comparisons of DNA sequences (nucleotide sequences encoding genes) or protein sequences (amino acid sequences encoding proteins)
• what does molecular data apply to?

  applies to all extant (living species, but not to extinct (fossils) species
• what is a phylogeny


  it is the evolutionary history of a species or group of related species
• what does a phylogenetic tree show

  shows hypotheses of the evolutionary relationship between organisms (past and present) between common ancestors and descendants
• what depicts evolutionary relationships in branching phylogenetic trees?

  systematists
• taxonomy is progressively being reorganized to reflect what

  phylogeny
• what are taxa

  group or level of organization into which organisms are classified
• what is a taxon


  a category into which related organisms are placed
• what is a node in a phylogenetic tree

  each branch point is a node and it represents the divergence of two species (speciation) and the common ancestors of those descendants
• what is a sister taxa


  groups that share an immediate common ancestor and is not shared with other taxa
• What is a rooted phylogenetic tree?

  includes a branch to represent the last common ancestor of all the taxa on the tree
• What is a basal taxon? (outgroup)


  diverges early in the history of the group and originates near the common ancestor of the group
• What is a polytomy in a phylogenetic tree?

  it is a branch from which more than two groups emerge. typically represent unresolved patterns of divergence
• what is a clade

  it is another word for branch and it is a group of taxa that includes an ancestor and all descendants (living and extinct) of that ancestor.
• what is a nested hierarchy of clades


  clades that are nested within one another
• why is a single terminal branch a valid clade

  because terminal taxa may represent a group of species and it includes all descendants of a single ancestor
• clades are often displayed as what

  collapsed/ pruned on the phylogenetic trees to aid interpretation
• what are the two kinds of phylogenetic trees

  • cladograms
  • phylograms
• what does a cladogram depict

  depicts evolutionary relationships where only branch order is important
• what two things convey no information in a cladogram

  • branch length
  • order of terminal taxa
• what does a phylogram depict

  depicts evolutionary patterns, but branch lengths are proportional to evolutionary change
• in a phylogram, what does branch length represent (2)

  • chronological time
  • number of character changes that took place between taxa in that lineage
• in a phylogram, what is a branch point determined from

  from the fossil record and/or molecular clock calculations based on changes in DNA sequences
• in a phylogram, the difference between two taxa is the sum of what


  sum of branch lengths since their common ancestor
• reading a phylogeny is similar to reading a what

  family tree
• in a phylogeny, what are lineage splits

  they are branching nodes on the phylogeny
• what does speciation give rise to

  gives rise to two descendant lineages
• what do phylogenies show patterns of

  patterns of ancestry between lineages
• in a phylogeny, each lineage has both what

  both unique ancestors and shared common ancestors
• the branching pattern of a tree indicates what


  indicates relatedness
• taxa that share more recent common ancestors are more what

  closely related
• in phylogenies does the order of terminal taxa indicate the relatedness of the taxa?

  no
• what do phylogenetic trees NOT show?

  • dont show evolutionary progress
  • doesn't show whether one taxa is more advanced than another taxa
• what do cladograms not indicate (2)

  they do not indicate when species evolved or how much change occurred in the lineage, they only show the pattern of descent