Phylogeny and Cladistics

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Phylogeny and Cladistics
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Which similarities are most important?

• Its not always easy to tell!
• Evolutionary classification classifying based
  on phylogeny, not just structural
  characteristics.
• Phylogeny the study of evolutionary
  relationships among organisms.

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Classification using Cladograms

• Many biologists now use a method called cladistic
  analysis.
• Cladistic analysis identifies and considers only
  new characteristics that arise as lineages (new
  line of organisms) evolve.
• Characteristics that appear in recent parts of a
  lineage but not in its older members are called
  derived characters.

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Cladogram
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Cladogram
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Check out this cladogram!
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Quick Lab p 453

• Complete the Quick Lab neatly to be added to your
  Lab book.
• Title How is a Cladogram constructed?
• Procedure a) Copy the chart titled Derived
  Characters in Organisms
• b) Identify the organism that
  is least closely related to the others.
• c) Construct a cladogram that
  includes the animals names and the appropriate
  derived characters
• Analyze and Conclude Answer the four questions
  in complete sentences
• Put your completed lab in your lab book and drop
  it in the drawer.

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Lets make a Cladogram

• Cladogram

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Other Characteristics used to indicate
Evolutionary connection

• Similarities in DNA can be used to help determine
  classification and evolutionary relationships.
• The more similar the DNA of two species, the more
  recently they shared a common ancestor, and the
  more closely they are related in evolutionary
  terms.
• The more two species have diverged from each
  other, the less similar their DNA will be.
• Read DNA Evidence on p. 454 looking at Figure
  18-8.

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Other Characteristics used to indicate
Evolutionary connection

• Molecular Clocks monitor neutral mutations
  that help estimate the length of time two species
  have been evolving independently.
• Read Molecular Clocks on p. 455.
• - In your notes, compare Positive, Negative and
  Neutral mutations.

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Molecular Clocks
Which species appear to be most closely related?
Where is Species B and Cs most recent
ancestor? Where is Species A and Cs most recent
ancestor? Lets go back to our earlier
animation Cladogram