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Classification and Taxonomy

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Title: Classification and Taxonomy Notes Feb 16 Author: dsherry Last modified by: D150 Created Date: 2/16/2012 12:49:58 PM Document presentation format – PowerPoint PPT presentation

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Title: Classification and Taxonomy


1
  • Classification and Taxonomy

2
THINK ABOUT IT
  • Scientists have been trying to identify, name,
    and find order in the diversity of life for a
    long time. The first scientific system for naming
    and grouping organisms was set up long before
    Darwin.
  • In recent decades, biologists have been
    completing a changeover from that older system of
    names and classification to a new strategy based
    on evolutionary theory.

3
Why Classify?
  • What are the goals of binomial nomenclature and
    systematics?
  • In binomial nomenclature, each species is
    assigned a two-part scientific name (genus and
    species).
  • The goal of systematics is to organize living
    things into groups that have biological meaning.

4
Why assign scientific names?
  • The first step in understanding and studying
    diversity is to describe and name each species.
  • By using a scientific name, biologists can be
    sure that they are discussing the same organism.
    Common names can be confusing because they vary
    among languages and from place to place.
  • For example, the names cougar, puma, panther, and
    mountain lion can all be used to indicate the
    same animal Felis Concolor.

5
Binomial Nomenclature
  • In the 1730s, Swedish botanist Carolus Linnaeus
    developed a two-word naming system called
    binomial nomenclature.
  • The scientific name usually is Latin. It is
    written in italics. The first word begins with a
    capital letter, and the second word is lowercased.

6
Binomial Nomenclature
  • The scientific name of the red maple is Acer
    rubrum.
  • The genus Acer consists of all maple trees.
  • The species rubrum describes the red maples
    color.

7
Classifying Species into Larger Groups
  • In addition to naming organisms, biologists try
    to organize, or classify, living and fossil
    species into larger groups that have biological
    meaning. Biologists often refer to these groups
    as taxa (singular taxon).
  • The science of naming and grouping organisms is
    called systematics.

8
Linnaean Classification System
  • How did Linnaeus group species into larger
    taxa?
  • Over time, Linnaeuss original classification
    system would expand to include seven hierarchical
    taxa species, genus, family, order, class,
    phylum, and kingdom.

9
Linnaean Classification System
  • Linnaeus also developed a classification system
    that organized species into a hierarchy, or
    ranking.
  • In deciding how to place organisms into larger
    groups, Linnaeus grouped species according to
    anatomical similarities and differences.

10
Seven Levels
  • Linnaeus identified just four levels in his
    original classification system.
  • Over time, Linnaeuss original classification
    system would expand to include seven taxa
    species, genus, family, order, class, phylum, and
    kingdom.

11
Problems With Traditional Classification
  • In a way, members of a species determine which
    organisms belong to that species by deciding with
    whom they mate and produce fertile offspring.
  • Ranks above the level of species, however, are
    determined by researchers who decide how to
    define and describe genera, families, orders,
    classes, phyla, and kingdoms.
  • Linnaeus grouped organisms into larger taxa
    according to overall similarities and
    differences. But which similarities and
    differences are the most important?

12
Problems With Traditional Classification
  • For example, adult barnacles and limpets live
    attached to rocks and have similar-looking
    shells.
  • Adult crabs dont look anything like barnacles
    and limpets.
  • Based on these features, one would likely
    classify limpets and barnacles together and crabs
    in a different group. However, that would be
    wrong.
  • Modern classification schemes look beyond
    overall similarities and differences and group
    organisms based on evolutionary relationships.

13
THINK ABOUT IT
  • Darwins ideas about a tree of life suggested
    a new way to classify organismsnot just based on
    similarities and differences, but instead based
    on evolutionary relationships.
  • When organisms are rearranged in this way, some
    of the old Linnaean ranks fall apart. To
    understand why, you need to know how evolutionary
    classification works.

14
Evolutionary Classification
  • What is the goal of evolutionary classification?
  • The goal of phylogenetic systematics, or
    evolutionary classification, is to group species
    into larger categories that reflect lines of
    evolutionary descent, rather than overall
    similarities and differences.

15
Evolutionary Classification
  • The concept of descent with modification led to
    phylogenythe study of how living and extinct
    organisms are related to one another.
  • Advances in phylogeny, in turn, led to
    phylogenetic systematics, or evolutionary
    classification. Phylogenetic systematics groups
    species into larger categories that reflect lines
    of evolutionary descent, rather than overall
    similarities and differences.

16
Common Ancestors
  • Phylogenetic systematics places organisms into
    higher taxa whose members are more closely
    related to one another than they are to members
    of any other group.
  • The larger a taxon is, the farther back in time
    all of its members shared a common ancestor.

17
Clades
  • A clade is a group of species that includes a
    single common ancestor and all descendants of
    that ancestorliving and extinct.
  • A clade must be a monophyletic group. A
    monophyletic group must include all species that
    are descended from a common ancestor, and cannot
    include any species that are not descended from
    that common ancestor.

18
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19
Cladograms
  • Modern evolutionary classification uses a method
    called cladistic analysis to determine how clades
    are related to one another.
  • This information is used to link clades together
    into a cladogram, which illustrates how groups of
    organisms are related to one another by showing
    how evolutionary lines, or lineages, branched off
    from common ancestors.

20
Cladograms
  • What is a cladogram?
  • A cladogram links groups of organisms by
    showing how evolutionary lines, or lineages,
    branched off from common ancestors.

21
Building Cladograms
  • This cladogram represents current hypotheses
    about evolutionary relationships among
    vertebrates.
  • Note that in terms of ancestry, amphibians are
    more closely related to mammals than they are to
    ray-finned fish!

22
DNA in Classification
  • How are DNA sequences used in classification?

23
New Techniques Suggest New Trees
  • The use of DNA characters in cladistic analysis
    has helped to make evolutionary trees more
    accurate.
  • For example, traditionally African vultures and
    American vultures were classified together in the
    falcon family.
  • Molecular analysis, however, showed that DNA
    from American vultures is more similar to the DNA
    of storks than it is to the DNA of African
    vultures.

24
New Techniques Suggest New Trees
  • Often, scientists use DNA evidence when
    anatomical traits alone cant provide clear
    answers.
  • For example, giant pandas and red pandas share
    many characteristics with both bears and
    raccoons.
  • DNA analysis revealed that the giant panda shares
    a more recent common ancestor with bears than
    with raccoons. Therefore, the giant panda has
    been placed in a clade with bears.
  • Red pandas, however, are in a clade with
    raccoons and other animals like weasels and
    seals.

25
Tree of Life
Fig 19.8
26
Changing Ideas About Kingdoms
  • This diagram shows some of the ways in which
    organisms have been classified into kingdoms
    since the 1700s.

27
The Tree of All Life
  • What does the tree of life show?
  • The tree of life shows current hypotheses
    regarding evolutionary relationships among the
    taxa within the three domains of life.

28
The Tree of All Life
  • Modern evolutionary classification is a rapidly
    changing science with the difficult goal of
    presenting all life on a single evolutionary
    tree.
  • The tree of life shows current hypotheses
    regarding evolutionary relationships among the
    taxa within the three domains.

29
The Tree of All Life
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