KEY CONCEPT Modern classification is based on evolutionary relationships.

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KEY CONCEPT Modern classification is based on
evolutionary relationships.
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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

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• Cladistics is a common method to make
  evolutionary trees.

• classification based on common ancestry
• species placed in order that they descended from
  common ancestor

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• A cladogram is an evolutionary tree made using
  cladistics.

• A clade is a group of species that shares a
  common ancestor.

• Each species in a clade shares some traits with
  the ancestor.
• Each species in a clade has traits that have
  changed.

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• Derived characters are traits shared in different
  degrees by clade members.

• basis of arranging species in cladogram
• more closely related species share more derived
  characters
• represented on cladogram as hash marks

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• Nodes represent the most recent common ancestor
  of a clade.

• Clades can be identified by snipping a branch
  under a node.

FEATHERS AND TOOTHLESS BEAKS.
SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW
OPENING IN THE SIDE OF THE SKULL
SKULL OPENINGS BEHIND THE EYE
EMBRYO PROTECTED BY AMNIOTIC FLUID
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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.