4. Method that groups
organisms that share
derived characteristics
The value or form of a
feature is referred to as a
character state
Relationships are portrayed
in straight line diagrams
Phylogenetic Systematics
5. HOMOLOGY
• traits have common
ancestry
• may/may not share
function
• may/may not look alike
HOMOPLASY
• traits are similar
because of
convergent
evolution
ANALOGY
• traits with common
function
• may/may not share
ancestry
• may/may not look
alike
6. Synapomorphies
• is a trait that is shared by 2 or more taxonomic groups
• is derived through evolution from a common ancestral
form
Plesiomorphic
• ancestral state
• character state that a taxon is inferred to have been
retained from its ancestors
Apomorphic
• derived state
• can be used to diagnose a clade – or even to define a
clade name in phylogenetic nomenclature
7. Cladistic Analysis
by Willi Hennig (1966)
is to determine which character states are
primitive and which are derived based on
common ancestry
8. Principles
Parsimony – states that any hypothesis that
requires fewer assumptions is a more
defendable hypothesis
Occam’s Razor - one should not make more
assumptions than the minimum needed to
explain anything
11. Cladogram
is an evolutionary tree which shows evolutionary
relationships by showing points at which lineages
diverged from common ancestral forms
is constructed such that the number of changes
from one character state to the next is minimized
is interpreted as that which requires the fewest
evolutionary changes in the taxa involved
12. Clade
a group of two or more taxa that includes
both their common ancestor and all their
descendants
13. FOUR LIMBS WITH DIGITS
Tetrapoda clade1
Amniota clade2
Reptilia clade3
Diapsida clade4
Archosauria clade5
EMBRYO PROTECTED BY AMNIOTIC FLUID
OPENING IN THE SIDE OF THE SKULL
SKULL OPENINGS IN FRONT OF THE EYE &
IN THE JAW
FEATHERS & TOOTHLESS
BEAKS.
SKULL OPENINGS BEHIND THE EYE
DERIVED CHARACTER
14. Node - a branch points based on
homologous, shared derived traits
Root - the common ancestor of all taxa
Branch - defines the relationship between
the taxa in terms of descent and ancestry
Branch length (scaled trees only) - represents
the number of changes that have occurred in
the branch
17. Outgroup Comparison
If the taxon that is not a member of the group
of organisms being classified has a character
state that is the same as some of the
organisms in the group then the character can
be considered plesiomorphic
20. Moss
(a) All of the plant groups shown here except mosses
have vascular
Pine
Daisy
Fern
Node
1
Common plant
ancestor
Common ancestor
with vascular tissues
26. Phyletic Group of Taxa
MONOPHYLETIC GROUP
Contains an ancestor and all of its
descendants - defined by > 1 shared,
derived traits.
POLYPHYLETIC GROUP
Does not include common ancestor
group. Common ancestor is placed
elsewhere
PARAPHYLETIC GROUP
Includes common ancestor but not all
of its descendants. Define by what it
lacks.
27.
28. WHY DO CLASSIFICATION SCHEMES CHANGE?
New Data
Rise of new technologies give new sources
of character information
New taxa
As previously unknown species are
discovered, classifications will also need to
be revised to reflect their placement