Warm-Up 3/24

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Warm-Up 3/24

• What is a derived characteristic?
• What is a clade?
• Circle a clade on the cladogram below.

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Chapter 18 Classification

• 18.2 Modern Evolutionary Classification

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Classification is Based on Evolutionary
Relationships (CLADISTICS)

• Phylogenythe study of how living and extinct
  organisms are related to one another.

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Cladograms

• Cladogram - is an evolutionary tree made using
  cladistics (ancestral relationships)
• More closely related species share the most
  derived characteristics

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Derived Characteristics

• Diagram uses derived characters to organize
  arrange species
• Derived Characteristic - a trait that arose in
  the most recent common ancestor of a particular
  lineage and was passed along to its descendants.

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Cladogram
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Clades

• Clade - a group of species that includes
• A single common ancestor
• All descendants of that ancestor, both living and
  extinct.
• Cannot include any species that are not descended
  from that common ancestor.

B is the ancestral species to I is the
ancestral species to
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Building Cladograms

• A speciation event ancestral lineage branched
  into two new lineages Branch point is called a
  node.
• The bottom of the tree represents the common
  ancestor shared by all organisms..

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Building Cladograms -2

• A cladograms branching patterns indicate degrees
  of relatedness among organisms.
• Which lineages are most closely related and why?
• 23
• 14
• 34
• 12

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Building Cladograms - 3

• Represents the current understanding about
  evolutionary relationships among vertebrates.
• Question Form one hypothesis about evolutionary
  relationships based off the cladogram below.

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Reading Cladograms

• This cladogram shows a simplified phylogeny of
  the cat family.

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Reading Cladograms Questions

• Which node represents the common ancestor of
  four-limbed animals in the cladogram?
• Branch point at Amphibians
• What does the order of the forks represent?
• Order in which various groups branched off over
  the course of evolution.
• All organisms on the cladogram share which
  derived characteristic?
• Four Limbs

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Reading Cladograms Questions

• Which derived character defines the clade
  Carnivora?
• Specialized shearing teeth
• Retractable claws is a derived character shared
  only by members of clade___________ .
• Felidae

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Cladogram
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Cladogram Facts

• Each derived character defines a clade.
• Derived characters that appear lower on the
  cladogram than the branch point for a clade are
  not derived for that particular clade.
• Is hair a derived character for the clade
  carnivora?
• No!!

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Cladograms Facts

• Smaller clades are nested within the larger
  clades.

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Clades and Traditional Taxonomic Groups

• Todays reptiles are all descended from a common
  ancestor.
• Modern birds, however, are also descended from
  that ancestor.

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Genes as Derived Characters

• All organisms carry genetic information in their
  DNA passed on from earlier generations.
• Wide ranges of organisms share a number of genes
  that can be used to determine evolutionary
  relationships.