Taxonomy%20and%20Phylogeny%20of%20Animals

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CHAPTER 10

• Taxonomy and Phylogeny of Animals

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Linnaeus and Taxonomy

• More than 1.5 million species of animals are
  named
• Estimated that these account for
• Less than 20 of all animals currently alive
• Less than 1 of extinct animals
• Taxonomy (aka - Systematics)
• Formal system for naming and classifying species
• Science of classifying organisms based on
  similarity, biogeography, molecular components,
  development, etc.

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Linnaeus and Taxonomy

• Greek philosopher Aristotle first classified
  organisms (350 BC)
• Carolus Linnaeus designed the current system of
  classification (1750)
• Swedish botanist with experience classifying
  flowers
• Used morphology (study of form and structure) to
  develop a classification system of animals and
  plants
• Divided animal kingdom into species and gave each
  a distinctive name
• Grouped species into genera, genera into orders,
  and orders into classes
• His classification scheme has been drastically
  altered, but the basic principle is still
  followed

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Carolus Linnaeus
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Linnaeus and Taxonomy

• Hierarchy of taxonomic ranks now includes 7
  major groups
• Kingdom, phylum, class, order, family, genus, and
  species
• Now, the new level of Domain is also used.
• All animals are placed in Kingdom Animalia, or
  Domain Eukarya
• Taxa (Taxon) - Groups of animals that share a
  particular set of characteristics.
• Example True Flies Diptera - single pair of
  wings
• Each rank can be subdivided into additional
  levels of taxa
• Superclass, suborder, etc.

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Division of Life - Milestones
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3 Domains - current proposal
Based on ribosomal RNA sequences
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Taxonomy

• Nomenclature assignment of a distinctive name to
  each species
• A scientific name of an animal consists of two
  words (binomial nomenclature)
• First word is the genus and is capitalized
• Second is the species written in lower case
• Scientific name should be printed in italics or
  underlined if handwritten
• Homo sapiens
• Homo sapiens

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Taxonomy

• Some animals are subspecies, usually caused by
  Geographic locations. They are referred to as
  trinomials (3 names)
• All three terms are in italics
• Subspecies is also in lower case

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• Ensantina eschscholtzii (salamander) has many
  subspecies.
• E.e. plantens, E.e. picta, E.e.croceater

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Taxonomic Characters and Phylogenetic
Reconstruction

• Cladogram
• Diagram illustrating hierarchy of clades (groups
  of animals with common ancestry)
• Outgroups used
• Phylogenetic tree (compared to cladogram)
• Additional information concerning
• ancestors,
• duration of lineages,
• amount of evolutionary change
• (some mathematical calculation and numerical
  values usually invovled)

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A cladogram
Amphioxus is the outgroup because it doesnt
share any of the defining characteristic with the
other taxa. What characteristic separates Bass
from Horses?
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Taxonomic Characters and Phylogenetic
Reconstruction

• Sources of Phylogenetic Information
• (What do we use to identify animals in a
  Phylogenetic Tree??)
• Comparative Morphology
• Examines shapes, sizes and development of
  organisms
• Skull bones, limb bones, scales, hair and
  feathers
• Living specimens and fossils are used

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Taxonomic Characters and Phylogenetic
Reconstruction

• Comparative Biochemistry
• Analyzes sequences of amino acids in proteins and
  nucleotides sequences in nucleic acids
• Comparative biochemistry can be applied to
  fossils
• Comparative Cytology
• Examines variation in number, shape and size of
  chromosomes
• Used almost exclusively on living specimens

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Phylogenetic Tree based On Cytology Comparing
base substitutions on Cyctochrome C (a
respiratory protein). s represent number of
Mutations that occurred at the ancestral
division.
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Animal Kingdom Patterns of Organization
Characteristics used to Classify

• Embryonic Tissue Layers
• Diploblastic - 2 tissues (ectoderm and endoderm)
• Triploblastic - 3 tissue layers (also mesoderm)
• Zygote Cleavage
• Protostome - blastopore becomes mouth
• Deuterostome - blastopore becomes anus

• Symmetry
• Asymmetrical (no central body point/axis) ex.
  sponge
• Bilateral (if divided right/left sides are mirror
  image) ex. vertebrates
• Radial (any plane cut through organism makes
  mirror image) ex. Sea anemone

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Major Subdivisions of the Animal Kingdom

• Traditional groupings based on embryological and
  anatomical characters
• Branch (Parazoa) phylum Porifera,
  the sponges and phylum Placozoa
• Branch (Eumetazoa) all other phyla

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Major Subdivisions of the Animal Kingdom

• Branch Eumetazoa
• Grade I (Radiata) phyla Cnidaria
• Grade II (Bilateria) all other phyla
• Division A (Protostomia) Mouth is first opening
• Subdivision of Protostomes by coelom formation
• Acoelomates phyla Platyhelminthes,
• Pseudocoelomates phyla Nematoda,
• Eucoelomates phyla Mollusca, Annelida,
  Arthropoda
• Division B (Deuterostomia) Anus is first
  opening
• phyla Echinodermata, Chordata