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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. 18.2 Modern Evolutionary Classification 18.2 Modern ... – PowerPoint PPT presentation

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Title: Warm-Up 3/24


1
Warm-Up 3/24
  • What is a derived characteristic?
  • What is a clade?
  • Circle a clade on the cladogram below.

2
Chapter 18 Classification
  • 18.2 Modern Evolutionary Classification

3
Classification is Based on Evolutionary
Relationships (CLADISTICS)
  • Phylogenythe study of how living and extinct
    organisms are related to one another.

4
Cladograms
  • Cladogram - is an evolutionary tree made using
    cladistics (ancestral relationships)
  • More closely related species share the most
    derived characteristics

5
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.

6
Cladogram
7
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
8
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..

9
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

10
Building Cladograms - 3
  • Represents the current understanding about
    evolutionary relationships among vertebrates.
  • Question Form one hypothesis about evolutionary
    relationships based off the cladogram below.

11
Reading Cladograms
  • This cladogram shows a simplified phylogeny of
    the cat family.

12
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

13
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

14
Cladogram
15
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!!

16
Cladograms Facts
  • Smaller clades are nested within the larger
    clades.

17
Clades and Traditional Taxonomic Groups
  • Todays reptiles are all descended from a common
    ancestor.
  • Modern birds, however, are also descended from
    that ancestor.

18
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.
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