Classification of Organisms

1
Classification of Organisms

• Chapter 14
• Read Section Reviews

2
Why Classify

• Taxonomy is the science of naming and classifying
  organisms.
• Scientists must use a classification system that
  names orders the organisms in a logical manner.
• There are two factors to a good classification
  system.
• Must have a universally accepted name.
• Place organisms in groups with real biological
  meaning.
• The groups are expected to share important
  traits.
• In the 1700s common names were replaced by Latin
  or ancient Greek names
• The names described the organisms were too
  long.
• This system was difficult to standardize.

3
Carolus Linnaeus

• Carolus Linnaeus developed Binominal
  Nomenclature.
• Every organism has a two part name.
• The first part is the genus it describes a
  small group to which the organism belongs.
• The second is the species usually describes a
  special trait.
• The genus is Capitalized and the species is lower
  case (usually in italics)
• There is a committee which oversees the naming
  process carefully selects a specimen.

4
How Linnaeus Creates his System

• Linnaeus organized all the known existing
  organisms into binomial nomenclature.
• He grouped organisms by shared body structures
• The groups he called Taxa (taxon)
• The science of naming these groups is called
  taxonomy.
• Linnaeus created an order from smallest to
  largest.

5
The Groups

• Listed from smallest to largest
• Species- shared traits but different biological
  units (may reproduce viable offspring)
• Genus- similar structures
• Family- groups of genus with some variation in
  structure.
• Order- several families make an order, still
  shared traits.
• Class- orders are placed in classes, I.e.
  mammalia
• Phylum- large group consisting of different
  animals yet share common characteristics
• Kingdom- Two giant Taxa separating plants and
  animals
• Domains- groups of similar Kingdoms

6
The Six Kingdom System

• Monera has been split into Eubacteria
  Archaebacteria which are prokaryotes. Early
  forms lacked nuclei, mitochondria, chloroplast
  and reproduced by binary fission
• Protista are single celled eukaryotes with
  membrane bound organelles. They are divided into
  three categories.
• Fungi cells have no cellulose in the cell walls,
  they are heterotrophic, and may have many nuclei
  in the same cell.
• Plantae multicellular, autotrophic, cell walls
  contain cellulose.
• Animalia multicellular, cell membrane but no cell
  wall, heterotrophic, and very diverse kingdom.

7
Hierarchy of Classification
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Organisms Hierarchy
9
Taxonomy Today

• Phylogeny is the evolutionary history of an
  organism.
• Organisms are grouped in Cladograms by
  evolutionary history not similarities in
  structures.
• Convergent Evolution can create organisms with
  analogous structures which are not closely
  related.
• Cladistics determines phylogenies by comparing
  and grouping organisms by characteristics
• Ancestral characteristics evolved in a common
  ancestor
• Derived characteristics evolved in the ancestors
  of one group but not the other.

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Phylogenic Diagram of Mammals
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Cladogram Mammals, Reptiles, and Birds
12
Cladogram Major Groups of Plants
13
Evolutionary Systematics

• Evolutionary Systematics provides varying degrees
  of importance to certain characteristics.
• Phylogenetic trees show this branching
  relationship between organisms.

14
Evolutionary Systematics and Cladistic Taxonomy