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Taxonomy

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Title: Taxonomy


1
Taxonomy Phylogeny
  • Introduction
  • Classification
  • Phylogeny
  • Cladograms
  • Quiz

2
In this tutorial, you will learn
  • The traditional classification scheme of
    Linnaeus.
  • Two theories of taxonomy
  • Traditional evolutionary taxonomy
  • Cladistics
  • How to read a cladogram

Credits Figures and images by N. Wheat unless
otherwise noted. Image of Linnaeus from
Wikipedia Funded by Title V-STEM grant
P031S090007.
3
Introduction
  • The practice of categorizing organisms according
    to similar features goes back to Aristotle.
  • The goal of Taxonomy today is to produce a formal
    system for naming and classifying species to
    illustrate their evolutionary relationships.

4
Classification vs. Systematization
  • In classification, the taxonomist asks whether
    the species being classified contains the
    defining feature of a certain taxonomic grouping.
  • Focus is on features.

5
Classification vs. Systematization
  • In systematization, the taxonomist asks whether
    the characteristics of a species support the
    hypothesis that it descends from the most recent
    common ancestor of the taxonomic group.
  • Focus is on evolutionary origin of those
    features.

6
Linnaeus and Classification
  • In the 18th century, Carolus Linnaeus designed
    the hierarchical classification system still in
    use today.
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

7
Taxa
  • Taxa (singular taxon) are the major groups of
    organisms.
  • Each rank can be subdivided into additional
    levels of taxa.
  • Superclass, suborder, etc.

8
Binomial Nomenclature
  • Binomial nomenclature is the system Linnaeus
    developed for naming species.
  • The two-part scientific name includes the genus
    and species
  • Names are latinized and italicized, only the
    genus is capatilized.
  • Sitta carolinensis

9
Phylogeny
  • The goal of systematics is to determine the
    phylogeny the evolutionary history of a
    species or group of related species.

10
Phylogeny
  • Phylogenies are inferred by identifying
    organismal features, characters, that vary among
    species.
  • These characters can be
  • Morphological
  • Chromosomal
  • Molecular
  • Behavioral or ecological

11
Homology
  • Homologous characters are shared characters that
    result from common ancestry.

12
Homoplasy
  • Homoplasies are shared characters that are not a
    result of common ancestry, but of independent
    evolution of similar characters (they are not
    homologous).
  • Can result from convergent evolution.

13
Convergent Evolution
  • Convergent evolution occurs when natural
    selection, working under similar environmental
    pressures, produces similar (analogous)
    adaptations in organisms from different
    evolutionary lineages.

14
Phylogeny
  • When trying to determine evolutionary
    relationships (inferring a phylogeny), we only
    want to consider homologous characters.
  • Homoplasies can create errors.

15
Shared Primitive and Shared Derived
Characteristics
  • Focusing on homologous structures, we need to
    determine when that character arose.
  • Newer characters tell us more!
  • Primitive (older) vs. derived (newer) characters

16
Shared Primitive and Shared Derived
Characteristics
  • A shared primitive character is a homologous
    structure that is older than the branching of a
    particular clade from other members of that
    clade.
  • It is shared by more than just the taxon we are
    trying to define.
  • Example mammals all have a backbone, but so do
    other vertebrates.

17
Shared Primitive and Shared Derived
Characteristics
  • A shared derived character is a new evolutionary
    feature, unique to a particular group.
  • Example - all mammals have hair, and no other
    animals have hair.
  • These are the features that are most useful for
    determining evolutionary relationships!

18
Ancestral Character States
  • The ancestral character state is the form of the
    character that was present in the common ancestor
    of the group.
  • Variations of the character that arose later are
    called derived character states.

19
Polarity
  • Polarity (which version of the trait is
    ancestral) is determined by using outgroup
    comparison.
  • An outgroup is closely related, but not part of
    the group being examined (the ingroup).

20
Polarity
  • An ancestral character is one that is found in
    both the study group and the outgroup.
  • Derived character groups are those found in the
    study groups but not the outgroups.

21
Clades
  • Clades are groups that share derived characters
    and form a subset within a larger group.
  • A clade is a unit of common evolutionary descent.

22
Synapomorphy
  • A synapomorphy is a derived character that is
    shared by all the members of the clade.
  • Using synapomorphies to define clades will result
    in a nested hierarchy of clades.

23
Symplesiomorphy
  • Ancestral character states for a taxon are called
    plesiomorphic.
  • Symplesiomorphies are shared ancestral
    characters.
  • Symplesiomorphies do not provide useful
    information for forming a nested series of clades.

24
Cladogram
  • The nested hierarchy of clades can be shown as a
    cladogram that is based on synapomorphies.

25
Monophyletic
  • A valid clade is monophyletic, it consists of the
    ancestor species and all its descendants.

26
Paraphyletic
  • A paraphyletic clade consists of an ancestral
    species and some, but not all, of the
    descendants.

27
Polyphyletic
  • A polyphyletic clade includes many species that
    lack a common ancestor.

28
Cladistics
  • Cladistics, also called phylogenetic systematics,
    is a taxonomic theory that is based on
    cladograms.
  • All taxa must be monophyletic!

29
Evolutionary Taxonomy
  • Traditional Evolutionary taxonomy is based on
    common descent and the amount of evolutionary
    change to rank higher taxa.
  • Sometimes this type of classification includes
    paraphyletic groupings.

30
Cladistics
  • Since all groupings must be monophyletic in
    cladistics, the paraphyletic arrangement of ape
    families doesnt work.
  • Humans, chimpanzees, gorillas, and orangutans are
    now all included together in one monophyletic
    family - Hominidae.

31
Sister Groups
  • A sister group is a pair of taxa that are most
    closely related to each other.
  • Humans are most closely related to chimpanzees,
    so humans chimpanzees form a sister group.
  • Gorillas form a sister group to the clade
    containing humans and chimpanzees.

32
Cladistics vs. Evolutionary Taxonomy
  • The important difference between these two
    theories of taxonomy is that traditional
    evolutionary taxonomy sometimes accepts
    paraphyletic clades, while cladistics does not.
  • Both accept monophyletic clades.
  • Both reject polyphyletic clades.

33
Who developed the classification system including
the binomial scientific name in use today?
Question 1
  • Darwin
  • Mendel
  • Linnaeus
  • Aristotle

34
Sorry!
Question 1
  • That is incorrect.
  • Try again!

35
Congratulations!
Question 1
  • You are correct!

36
Which of the following are considered to be taxa?
Question 2
  • Phylum
  • Class
  • Family
  • Species
  • All of the above

37
Sorry!
Question 2
  • That is incorrect.
  • Try again!

38
Congratulations!
Question 2
  • You are correct!

39
Which example of binomial nomenclature is
formatted correctly?
Question 3
  • Homo sapiens
  • homo sapiens
  • Homo Sapiens
  • Homo Sapiens
  • It doesnt matter, they are all correct

40
Sorry!
Question 3
  • That is incorrect.
  • Try again!

41
Congratulations!
Question 3
  • You are correct!

42
Which of these terms is associated with
characters that share common ancestry.
Question 4
  • Homology
  • Convergent evolution
  • Homoplasy
  • Analogy
  • All of the above

43
Sorry!
Question 4
  • That is incorrect.
  • Try again!

44
Congratulations!
Question 4
  • You are correct!

45
When defining a clade, what type of characters
should we use?
Question 5
  • Homoplasies
  • Shared primitive characters symplesiomorphies
  • Shared derived characters synapomorphies
  • All of the above

46
Sorry!
Question 5
  • That is incorrect.
  • Try again!

47
Congratulations!
Question 5
  • You are correct!

48
The branching diagram that illustrates the
nesting hierarchy of clades is called a
Question 6
  • Family tree
  • Cladogram
  • Phylogenetic diagram
  • Taxonomic web

49
Sorry!
Question 6
  • That is incorrect.
  • Try again!

50
Congratulations!
Question 6
  • You are correct!

51
A monophyletic clade is one that contains
Question 7
  • An ancestor and all of its descendants.
  • An ancestor and some of its descendants.
  • Several species that lack a common ancestor.
  • One species.

52
Sorry!
Question 7
  • That is incorrect.
  • Try again!

53
Congratulations!
Question 7
  • You are correct!

54
A polyphyletic clade is one that contains
Question 8
  • An ancestor and all of its descendants.
  • An ancestor and some of its descendants.
  • Several species that lack a common ancestor.
  • One species.

55
Sorry!
Question 8
  • That is incorrect.
  • Try again!

56
Congratulations!
Question 8
  • You are correct!

57
A paraphyletic clade is one that contains
Question 9
  • An ancestor and all of its descendants.
  • An ancestor and some of its descendants.
  • Several species that lack a common ancestor.
  • One species.

58
Sorry!
Question 9
  • That is incorrect.
  • Try again!

59
Congratulations!
Question 9
  • You are correct!

60
This cladogram illustrates a ________________
clade.
Question 10
  • Monophyletic
  • Paraphyletic
  • Polyphyletic
  • None of the above

61
Sorry!
Question 10
  • That is incorrect.
  • Try again!

62
Congratulations!
Question 10
  • You are correct!

63
Which of the following statements about the
difference between cladistics and traditional
evolutionary taxonomy is false?
Question 11
  • Both accept monophyletic clades
  • Both accept paraphyletic clades
  • Cladistics rejects paraphyletic clades, while
    evolutionary taxonomy sometimes accepts them.
  • Both reject polyphyletic clades.

64
Sorry!
Question 11
  • That is incorrect.
  • Try again!

65
Congratulations!
Question 11
  • You are correct!

66
Which of the following cladograms incorrectly
illustrates sister groups?
Question 12
67
Sorry!
Question 12
  • That is incorrect.
  • Try again!

68
Congratulations!
Question 12
  • You are correct!
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