Classification and Phylogeny of Animals

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Chapter 10
Classification and Phylogeny of Animals
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Outline

• Intro
• Classification basics
• Species concepts
• Phylogenetic reconstruction
• Theories in taxonomy
• Divisions of life and subdivisions of Animalia

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Intro

• 1.5 M animal sp.
• lt 20 sp. named so far?
• classified based on evolutionary relationships
• Darwins theory of common descent is underlying
  principle for taxonomy
• taxonomy study of classificaiton, systematic
  ordering/naming of organisms
• part of systematics/comparitive biology
• taxonomy modified w/ advent of evolutionary
  biology/DNA

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Classification Basics

• Aristotle 1st to classify organisms based on
  morphology
• Linnaeus
• Swedish botanist, designed classification scheme
  used today
• published in Systema Naturae, used morphological
  characteristics
• hierarchical system, binomial nomenclature
• genus (noun), species epithet (adjective)
• authority person who 1st describes sp. and
  publishes sp. name
• examples
• currently 7 mandatory ranks for all animal sp.,
  30 optional
• KPCOFGS

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Species

• No simple definition of species thus have
  multiple sp. concepts
• Agreed-on criteria for sp.
• common descent
• smallest distinct grouping
• shares morphological/genetic characteristics
• reproductive community
• isolated from other sp.
• interbreeding required for sexually reproducing
  sp.
• occupation of particular ecological habitat
• Distribution of sp. in space geographic range
• cosmopolitan sp. very large range/distribution
• endemic sp. very restricted range/distribution
• Distribution of sp. in time evolutionary
  duration

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Species Concepts

• Morphological (typological) sp. concept
• sp. defined by fixed, essential (usually
  morphological) features
• historical sp. concept, now use molecular
  evidence
• type specimen ideal representative of sp.,
  labeled and held in museum
• problems
• sibling sp. very similar morphologically but
  different genetically
• Biological sp. concept
• sp. defined as reproductive community of
  populations that occupy specific niche (a.k.a.
  reproductive isolation)
• an interbreeding population
• emerged during 30s-40s, formulated by
  Dobzhansky and Mayr
• problems
• lacks explicit temporal dimension (good for
  current sp. but difficult to use to relate to
  ancestors)
• degree of reproductive isolation controversial
  (hybridizations)
• what about asexually reproducing sp.?

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Species Concepts

• Evolutionary sp. concept
• a single lineage of ancestor-descendant
  populations that maintains its identity from
  other such lineages and that has its own
  evolutionary tendencies and historical fate
• proposed 1940s by Simpson
• useful for ancestral sp.
• based on morphological features from fossils
• abrupt changes in features demark boundaries of
  sp.
• Phylogenetic sp. concept
• basal grouping of organisms diagnosably distinct
  from other such groupings and within which there
  is a parental pattern of ancestry and descent
• phlyo. sp. single population lineage w/ no
  detectable branching
• focuses on smallest grouping of organisms
• results in ? sp.

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Taxonomic Characters

• Systematics science of classification and
  reconstruction of phylogeny
• phylogeny origin and diversification of any
  taxon
• evolutionary history
• based on varying morphological, chromosomal,
  molecular characters (indentifying features)
• sometimes behavioral, ecological characters
• phylogenetic analysis depends on finding shared
  features from common ancestor
• homology character similarity from common
  ancestry
• nonhomologous similarity (homoplasy) character
  similarity from different ancestry