1. KEY CONCEPT Modern classification is based on evolutionary relationships.

2. Cladistics is classification based on common ancestry.
Phylogeny is the evolutionary history for a group of species.
evidence from living species, fossil record, and molecular data
shown with branching tree diagrams
- constructed by identifying derived characters

3. Cladistics is a common method to make evolutionary trees.
classification based on common ancestry
species placed in order that they descended from common ancestor

4. A cladogram is an evolutionary tree made using cladistics.
A clade is a group of species that shares or descended from a common ancestor.
Each species in a clade shares some traits with the ancestor.
Each species in a clade has traits that have changed.

5. basis of arranging species in cladogram
Derived characters are traits shared in different degrees among species (by clade members).
FOUR LIMBS WITH DIGITS
Tetrapoda clade 1
Amniota clade 2
Reptilia clade 3
Diapsida clade 4
Archosauria clade 5
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
basis of arranging species in cladogram
more closely related species share more derived characters
represented on cladogram as hash marks

6. Nodes represent the most recent common ancestor of a clade.
FOUR LIMBS WITH DIGITS
CLADE
Tetrapoda clade 1
Amniota clade 2
Reptilia clade 3
Diapsida clade 4
Archosauria clade 5
FEATHERS AND TOOTHLESS BEAKS.
SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW
Clades can be identified by snipping a branch under a node.
OPENING IN THE SIDE OF THE SKULL
SKULL OPENINGS BEHIND THE EYE
EMBRYO PROTECTED BY AMNIOTIC FLUID
DERIVED CHARACTER
NODE

7. Molecular evidence reveals species’ relatedness.
Molecular data may confirm classification based on physical similarities.
Molecular data may lead scientists to propose a new classification.
DNA is usually given the last word by scientists.