Week 3 - Reconstructing relationships

Reading assignment


CLASSIFICATION

Web Links

  1. classification from the University of Minnesota, General Zoology
  2. Using the Evidence of Evolution: Classifying life.  A great overview from Kimball's Biology Pages
Carolus Linnaeus (1707-1778)

ESTABLISHING RELATIONSHIPS

Schools of Taxonomy by M. Alan Kazlev

Numerical Taxonomy

Evolutionary Taxonomy by GŁnter Bechly 

Phylogenetic Systematics

Inferring Phylogeny from Morphological Data

Establishing relationships depends on the recognition of homologous characters, which evolved from a common ancestor.  Uniquely derived character states reflect common ancestry; e.g. amnion, feathers

Terminology

character:
recognizable attribute
apomorphy:
derived or specialized character
plesiomorphy
primitive or ancestral character
autapomorphy
characterizes a terminal branch only
synapomorphy
shared derived character inferred to have originated in the latest common ancestor
sister groups:
two monophyletic groups share a common ancestry ancestry with each other more recently than either one does with any other taxa
monophyletic:
entire phylogeny; latest common ancestor plus all and only all its descendants
paraphyletic:
group including the most recent common ancestor of all members of the group; but from which one or more descendent groups have been excluded; can not be defined strictly by synapomorphies; part of phylogeny; e.g. Class Reptilia; stem groups
polyphyletic:
descendents of unrelated ancestors; does not include the common ancestor of at least two taxa; taxa are grouped together because of convergent evolution

Determining Monophyly

clade:
monophyletic group

homologous:

  1. character state inherited from common ancestor (e.g. ostrich and robin wings; bones in [analogous] bird, bat, & pterosaur wing)
  2. homology is determined by position relative to other structures; development (embryological tissue, pattern of ontogeny) & evolution

analogous: similar function; arose independently

convergent evolution: similar features from different ancestors

parallel evolution: independent modifications from the same ancestor; e.g. elongate body of salamanders by independent evolution of extra vertebrae; ?burrowing rodents.

homoplasy: character similarity that misrepresents common descent as a result of convergence, parallelism, or reversal

molecular phylogeny

molecular clock


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