Phylogeny and Systematics
2.10.15
Phylogeny
• Evolutionary history of a species of a group of
related species
• Information used to construct phylogenies
includes:
– Fossil record
– Molecular comparison (DNA, RNA, proteins)
– Breeding behavior/embryological development
– Biogeography
– Morphology
Systematics
• The study of biological diversity in an
evolutionary context
• Encompasses taxonomy, goal is to trace
phylogeny
• Modern phylogenetic systematics =
classification based on evolutionary history
Cladogram
• Phylogenetic diagram based on cladistics
– Cladistics = form of taxonomy based on shared
characteristics not found in ancestral group
– Clade = evolutionary branch in cladogram; consists
of ancestral species and all descendants
Clade
• A clade consists of ancestral species & all
descendants
– Grouping of species is known as monophyletic if it
meets this standard
– Circle the monophyletic group that includes
organisms E and H:
Clade
• A clade consists of ancestral species & all
descendants
– Grouping of species is known as monophyletic if it
meets this standard
– Circle the monophyletic group that includes
organisms E and H:
Non-monophyletic groups:
Constructing a cladogram:
#1: Sort homology from analogy
• Homology:
– Similar structure and
shared ancestry
– The greater # of
homologous parts the
more closely related
• Analogy:
– Different structure;
similar function (wings
of birds vs. butterflies vs.
bats)
– Come to resemble each
other because
experience similar
environmental pressures
#2: Identify shared derived characters
Shared primitive characters
• Not limited to group being
studied
• Example: backbone &
mammals (backbones not
limited to mammals)
Shared derived characters
• Evolutionary novelty unique
to clade
• Example: hair is unique to
mammals
#3: Outgroup comparison
• Outgroup = species closely related to species
being studied
• Ingroup = species being studies
– Identify characteristics to be studied
– Create data matrix comparing characteristics
– Construct cladogram
Example
Example
Example
Example from molecular data
Example from molecular data
Example from molecular data