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Classification of Organisms


Classification of Organisms Biology- Chapter 18 (508-533) Modern Bio Chapter 17 (336-351) Biology Concepts and Connections Chap 15 (304-310) Web cd 15c – PowerPoint PPT presentation

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Title: Classification of Organisms

Classification of Organisms
  • Biology- Chapter 18 (508-533)
  • Modern Bio Chapter 17 (336-351)
  • Biology Concepts and Connections Chap 15
  • Web cd 15c

18.1 Finding Order in Diversity 18.2 Modern
Evolutionary Classification 18.3 Building the
Tree of Life
  • Relate biodiversity to biological classification
  • Explain why naturalist replaced Aristotle's
    classification system
  • Identify the main criterion that Linnaeus used to
    classify organisms
  • List the common levels of modern classification
    from general to specific

  • Biologists have named and classified almost 2
    million species. However, they estimated that the
    total number of species on Earth is much greater.
    Over time, Scientist have created various systems
    of classification to organize their knowledge of
    the tremendous number of species. Each system
    places species into categories bases on
    particular characteristics

Classifying Organisms
  • biodiversity- the variety of organisms considered
    at all levels from populations to ecosystems
  • Continues to grow everyday ? not complete
  • Erwin cataloging insects, over 1000 beetles, 30
    million species of insects ww

  • sciences of describing , naming, and classifying
  • Taxon or taxa- group with in a taxonomic system
  • Aristotle, Greek philosopher, classified
    organisms into only 2 taxa
  • 1. animals-land, air, or water,
  • 2. Plant- based on stems
  • ?As it progresses they realized it was not
    working well

Linnaean System
  • Carolus Linnaeus, Swedish naturalist (1707-1778)
  • Developed a system of grouping organisms into
    hierarchical categories according to their form
    and structure
  • Simple to complex, 7 categories
  • Domain, Kingdom, Phylum, Class, Order, Family,
    Genus, Species
  • Did King Philip Come Over For Grape Soda
  • Can you do your own?

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Levels of Classification pg1079
  1. Domains- prokaryotes or eukaryotes- Eukarya
  2. Kingdom- animals or plants- Animalia
  3. Phyla (animals) or divisions (plants) Chordata
  4. Classes-Mammalia
  5. Orders- Carnivora
  6. Family- Felidae
  7. Genus- Felis
  8. Species (Felis catus, domestic cat)

Binomial Nomenclature
  • Linnaeus gave organisms a species name or a
    scientific name that contained 2 parts
  • Linnaeus grouped species according to anatomical
    similarities and differences.
  • 2 Parts
  • 1. genus Homo
  • 2. species identifier sapiens
  • Species name is written in italics and the genus
    name capitalized, tend to come from Latin roots

Binomial Nomenclature
  • The polar bear, for example, is called Ursus
  • The first part of the nameUrsusis the genus to
    which the organism belongs. A genus is a group of
    similar species. The genus Ursus contains five
    other species of bears, including Ursus arctos,
    the brown bear or grizzly bear.
  • The second part of a scientific namemaritimus
    for polar bearsis unique to each species and is
    often a description of the organisms habitat or
    of an important trait. The Latin word maritimus
    refers to the sea polar bears often live on pack
    ice that floats in the sea.
  • The scientific name of the red maple is Acer
  • The genus Acer consists of all maple trees.
  • The species rubrum describes the red maples

Problems With Traditional Classification
  • For example, adult barnacles and limpets live
    attached to rocks and have similar-looking
  • 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
  • Modern classification schemes look beyond
    overall similarities and differences and group
    organisms based on evolutionary relationships.

  • More than 200 years ago, Linnaeus grouped
    organisms according to similarities that he could
    readily see. Modern biologists consider not only
    visible similarities but also similarities in
    embryos, chromosomes, proteins, and DNA. In
    systematic, the goal is to classify organisms in
    terms of their natural relationships.

  • Identify the kinds of evidence that modern
    biologists use in classifying organisms
  • Explain what information a phylogenetic diagram
  • State the criteria used in cladistic analysis
  • Describe how a cladogram is made
  • Explain cladistic taxonomy, and identify one
    conclusion that is in conflict with classical

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.
  • 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.

  • The analysis of the evolutionary or ancestral
    relationships among taxa
  • Use phylogenetic diagram or tree
  • They can change due to new discoveries and
  • Determine if any evidence of shared ancestry

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

  • System of phylogenetic analysis that uses shared
    and derived characters
  • Shared character- is a feature that all members
    of a group have in common, such as hair in
    mammals or feathers in birds
  • Derived character- feature that evolved only
    within the group under consideration, feathers
    evolved with in birds
  • Clad- group of organisms that includes an
    ancestor plus all of its descendants
  • Cladogram- chart developed
  • Fig 17.3

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

Derived Characters
  • Whether or not a character is derived depends on
    the level at which youre grouping organisms.
    Four limbs, for example, is a derived character
    for the clade tetrapoda. Hair is a derived
    character for the clade Mammalia, but four limbs
    is not derived for mammals. If it were, only
    mammals would have four limbs!
  • Specialized shearing teeth is a derived character
    for the clade Carnivoraof which both the coyote
    and lion are members. Neither hair nor four limbs
    is a derived character for this clade.
  • Retractable claws is a derived character for the
    clade Felidae (the cats). Notice that lions have
    this trait, but coyotes do not.

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

Clades and Traditional Taxonomic Groups
Two clades do include the birds clade Aves, (the
birds themselves), and clade Reptilia. Therefore,
according to cladistics, a bird is a reptile!
New Techniques Suggest New Trees
  • The use of DNA characters in cladistic analysis
    has helped to make evolutionary trees more
  • 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

New Techniques Suggest New Trees
  • Often, scientists use DNA evidence when
    anatomical traits alone cant provide clear
  • For example, giant pandas and red pandas share
    many characteristics with both bears and
  • 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

  • The process of identifying and naming all known
    organisms, both living and extinct, is a huge
    first step toward the goal of systematics.
  • The real challenge, however, is to group
    everythingfrom bacteria to dinosaurs to blue
    whalesin a way that reflects their evolutionary
  • Over the years, new information and new ways of
    studying organisms have produced major changes in
    Linnaeuss original scheme for organizing living

Modern Classification
  • Biologist continue to develop taxomies to
    organize lifes enormous diversity. They
    regularly revise the many branches of the tree
    of life to reflect current hypotheses of the
    evolutionary relationships between groups. They
    have revised the larges and most fundamental
    categories of the Linnean-inspired classification
    system- domains and kingdoms.

  • Describe the evidence that prompted the invention
    of the three-domain system of classification
  • List the characteristics that distinguish between
    the domains Bacteria, Archaea, Eukarya
  • Describe the 6-kingdom system of classification
  • Identify problematic taxa in the 6-kingdome
  • Explain why taxonomic systems continue to change.

Changing Ideas About Kingdoms
  • During Linnaeuss time, living things were
    classified as either animals or as plants.
  • Animals were organisms that moved from place to
    place and used food for energy.
  • Plants were green organisms that generally did
    not move and got their energy from the sun.
  • As biologists learned more about the natural
    world, they realized that Linnaeuss two
    kingdomsAnimalia and Plantaedid not reflect the
    full diversity of life.

Changing Ideas About Kingdoms
  • Classification systems have changed dramatically
    since Linnaeuss time, and hypotheses about
    relationships among organisms are still changing
    today as new data are gathered.

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  • Domains Bacteria, Archaea, Eukarya
  • Kingdoms
  • a. Eubacteria
  • b. Archaebacteria
  • c. Protista
  • d. Fungi
  • e. Plantae
  • f. Animalia

The Tree of All Life
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Domain Bacteria
  • Members of the domain Bacteria are unicellular
    and prokaryotic. This domain corresponds to the
    kingdom Eubacteria.
  • Their cells have thick, rigid walls that
    surround a cell membrane and contain a substance
    known as peptidoglycan.
  • These bacteria are ecologically diverse, ranging
    from free-living soil organisms to deadly
    parasites. Some photosynthesize, while others do
    not. Some need oxygen to survive, while others
    are killed by oxygen.

Domain Archaea
  • The domain Archaea corresponds to the kingdom
  • Members of the domain Archaea are unicellular
    and prokaryotic, and they live in some extreme
    environmentsin volcanic hot springs, brine
    pools, and black organic mud totally devoid of
    oxygen. Many of these bacteria can survive only
    in the absence of oxygen.
  • Their cell walls lack peptidoglycan, and their
    cell membranes contain unusual lipids that are
    not found in any other organism.

Domain Eukarya
  • The domain Eukarya consists of all organisms
    that have a nucleus. It comprises the four
    remaining kingdoms of the six-kingdom system
    Protista, Fungi, Plantae, and Animalia.

The Protists Unicellular Eukaryotes
  • The kingdom Protista has long been viewed by
    biologists as a catchall group of eukaryotes
    that could not be classified as fungi, plants, or
  • Recent molecular studies and cladistic analyses
    have shown that the eukaryotes formerly known as
    Protista do not form a single clade. Current
    cladistic analysis divides these organisms into
    at least five clades.
  • Since these organisms cannot be properly placed
    into a single taxon, we refer to them as

The Protists Unicellular Eukaryotes
  • Most protists are unicellular, but one group,
    the brown algae, is multicellular.
  • Some protists are photosynthetic, while others
    are heterotrophic.
  • Some display characters that resemble those of
    fungi, plants, or animals.

  • Members of the kingdom Fungi are heterotrophs
    with cell walls containing chitin.
  • Most fungi feed on dead or decaying organic
    matter. They secrete digestive enzymes into their
    food source, which break the food down into
    smaller molecules. The fungi then absorb these
    smaller molecules into their bodies.
  • Mushrooms and other recognizable fungi are
    multicellular, like the ghost fungus shown. Some
    fungiyeasts, for exampleare unicellular.

  • Members of the kingdom Plantae are
    multicellular, have cell walls that contain
    cellulose, and are autotrophic.
  • Autotrophic plants are able to carry on
    photosynthesis using chlorophyll.
  • Plants are nonmotilethey cannot move from place
    to place.
  • The entire plant kingdom is the sister group to
    the red algae, which are protists. The plant
    kingdom, therefore, includes the green algae
    along with mosses, ferns, cone-bearing plants,
    and flowering plants.

  • Members of the kingdom Animalia are
    multicellular and heterotrophic.
  • Animal cells do not have cell walls.
  • Most animals can move about, at least for some
    part of their life cycle.
  • There is incredible diversity within the animal
    kingdom, and many species of animals exist in
    nearly every part of the planet.