Transcript Modern Phylogenetic Taxonomy 18-2

Modern Evolutionary
Classification
18-2
I. Evolutionary Classification
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A. Phylogeny – Scientist now group
organisms into categories that represent
lines of evolutionary decent or evolutionary
relationships among organisms, not just by
physical similarities.
B. The higher the level of the taxon the
further back in time are the common
ancestor of all the organisms in that taxon.
C. Animals that appear very similar may
not share a recent common ancestor, at
all. Example - Dolphin
Plant Phylogeny
Primate Phylogeny
Animal (Invertebrate) Phylogeny
Animal (Vertebrate) Phylogeny
II. Classification Using
Cladograms
A. Cladistic Analysis – Identifies and
considers only those characteristics that
appear in recent parts of a lineage not in
older members. These are called
derived characters. Unique
Characteristics ( these are used to
construct cladograms.)
1. A diagram that shows evolutionary
relationships among a group of
organisms.
Cladistics
III. Similarities of DNA and
RNA
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A. The more similar the DNA
sequence of two species , the
more recently they shared a
common ancestor and the
more closely they are related
in evolutionary terms.
VI. Molecular Clock
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A. Uses DNA comparisons to
estimate the length of time
that two species have been
evolving independently or have
been separated.
B. The longer in time 2 species
descended from a common
ancestor, the more different their
genes are likely to be.