Chapter 25/26 Taxonomy and Biodiversity

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Chapter 25/26Taxonomy and Biodiversity

• Evolutionary biology
• The major goal of evolutionary biology is to
  reconstruct the history of life on earth
• ?Process a- natural selection
• b- mechanisms that change the
  genetic composition
• of populations (evolution
  of new species)
• ?History
• Phylogeny, the evolutionary history of a group of
  organisms
• Systematics, an analytical approach to
  understanding the diversity and relationships of
  living and extinct organisms

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Phylogenetic Systematics Connecting
Classification with Evolutionary History

• Carolus Linnaeus (1748) published Systema
  naturae
• - classification of all plants and animals known
  at the time, Binomial naming of living organisms
  (Genus name and Species name)
• Taxonomy is an ordered division of organisms into
  categories based
• on similarities and
  differences
• Linneauss classification based on resemblances
  between organisms
• (not
  based on evolutionary relationships)
• Taxonomy employs a hierarchical system of
  classification-
• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• 
  Species

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Linnaeus in his Systema naturae

• What is SPECIES
• Species is a largest group of organisms that have
  common similar phenotype but they have to be
  capable to sexually reproduces (i.e. to combine
  their genetic material) and produce fertile
  progeny.
• A- Each species has a two-part name,
  binomial
• Genus, is the closest group to which a
  species belongs
• Species (specific epithet, meaning
  nickname or description
• refers to a one
  species within each genus )
• B- Species are organized hierarchically
  into
• broader and broader groups of
  organisms
• Note The first letter of the genus is
  capitalized and both names are italicized and
  Latinized
• Example, Humans (WE men and women) are
  named
• Homo sapiens, The wise man.
  

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Hierarchical Classification

• Means grouping species into increasingly broad
  taxonomic categories
• Species that appear to be closely related are
  grouped into the same genus
• Genera are grouped into progressively broader
  categories
• Family, Order, Class, Phylum, Kingdom, and
  Domain (or Superkingdom)
• Taxon Taxonomic unit at any level
• Example Panthera is a taxon at the genus level,
• Mammalia is a taxon at the class
  level
• (Mammalia includes all of the
  many orders of mammals)

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• Note Higher classification levels (Genus and
  above) are not defined by some measurable
  characteristic. ( remember Biological Species
  are separated by the reproductive isolation)
• The larger categories are not comparable between
  lineages (ancestries).
• An order of snails does not necessarily exhibit
  the same degree of morphological or genetic
  diversity as an order of mammals

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New information and understanding of the tree of
life

• The Molecular Data and the evolutionary
  relationships of lifes diverse forms
• The first taxonomic schemes a- plant kingdom
• b-
  animal kingdom
• Whittaker R. H.(1969), Five-kingdom system
• Monera
• Protista
• Plantae
• Fungi
• Animalia
• Basically Two fundamentally different types of
  cells
• Prokaryotic (the kingdom
  Monera)
• Eukaryotic (the other four
  kingdoms)

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• kingdoms Plantae, Fungi and Animalia
  (multicellular eukaryotes) distinguished by
  nutrition
• Plants are autotrophic, making organic food by
  photosynthesis
• Most fungi are decomposers with extracellular
  digestion and absorptive nutrition.
• Most animals ingest food and digest it within
  specialized cavities
• Protista includes all eukaryotes that did not fit
  the definition of plants, fungi, or animals.
• Most protists are unicellular. But some are
  multicellular organisms (Seaweeds, because of
  their relationships to specific unicellular
  protists)
• Note The five-kingdom system prevailed in
  biology for more than 20 years
• But it was challenged by-
• A- Molecular Data led to a- Cladistic
  analysis to taxonomy,
• b-
  Cladograms
• B- Systematists sorting out Protista based on
  their phylogeny
• into five or more new kingdoms or assigned
  into the Plantae, Fungi, or Animalia

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• Cladistic- Cladistic meaning the study of
  resemblances among a clade.
• Clade- Clade is a group of species that includes
  an ancestral species and all its descendents.
• Cladogram- Cladogram is a diagram which
  represents patterns of shared characteristics
• The Molecular data led to-
• Three-domain system as Superkingdoms.
• Bacteria,
• Archaea,
• Eukarya
• Bacteria differ from Archaea in many key
  structural, biochemical, and physiological
  characteristics.
• Many microbiologists divided Bacteria and Archea
  into multiple kingdoms based on cladistic
  analysis of molecular data

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• Taxonomy always is a work in progress
• Much more research is needed for-
• How the three domains of life are
• related?
• How many kingdoms should be included
• in each domain?
• Note New data, including the discovery of new
  groups, will lead to further taxonomic
  remodeling.
• Keep in mind-
• Phylogenetic trees
• Taxonomic groupings
• Both are hypotheses that fit the best available
  data

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