Chapter Introduction

• Anatomy (how it works)

  • study of structure and has emphasis on individual parts
  • analytical
  • Observational & description
• Morphology (why? How?)

  • study of shape and has emphasis on the total body
  • has underlying themes and concepts of symmetry
  • synthetic
• Comparative anatomy

  • differences & similarities in structure of various organisms
  • used in phylogenetic studies
• Functional Morphology

  • Relationship between anatomical design of a structure and the functions it performs
  • experimental - how does this work in the living organism
• Systematics -

  • branch of science
  • putting order to biodiversity
• Taxonomy

  • Applying names to organisms
• Classification

  • naming groups of organisms (holds multiple species)
• Nomenclature

  • how do we name things - deals with naming
• Phylogeny

  • a tree- like model of evolutionary relationship
• Phylogenetics

  • the practice of constructing phylogenies
• Cladogram

  • a particular type of phylogeny
• Cladistics

  • the practice of constructing cladograms
• Phylogenetics

  • can be constructed using extant organisms
  • all organisms are modified descendents of ancestors
  • Characters of living organisms are in an evolved state, a modification from an ancestral (primitive) state
  • examining characters we can build up a model of interrelationships based on shared derived characters
• Homologous Characters

  • share common ancestry

  
• Homologous characters

  • function and appearance can change dramatically through evolution (origin of the inner ear bones)

  
• Embryology

  • study of formation and development
  • can often illustrate homology
  • (inner ear bones of a mouse embryo)

  
• Phylogenetics - Analogy

  • characters that are similar due to similar selective pressures NOT common ancestry
• Parallelism

  • special type of analogy in which characters and appearances are the same but evolved independently (analogous NOT homologous)
• • Divergent evolution - new morphologies (green)
  • Convergent evolution - similar evolutionary pressure, distinctly different ancestors (red)
  • Parallelism - close ancestors, similar evolutionary pressure (blue)

  
• Homology

  • common ancestry may not be similar in either function or appearance
• Analogy

  • similar in function, careful inspection usually reveals dissimilarity of appearance
• Homoplasy

  • similarity of appearance, may not be similar in function
• Plesiomorphy (Primitive character)

  • a primitive character state, or similar to what a common ancestor had
  • plesiomorphies in the outgroup are referred to as state 0
• Apomorphy (derived character)

  • an evolved character state, or different than what the common ancestor had
  • apomorphies in the ingroup are referred to as state 1
• In group

  • taxonomic group we are interested in (vertebrates)
• Outgroup

  • a sister taxon (closely related) that will be used to determine direction of evolution of characters
• Characters

  • morphological - based on comparative anatomy
  • comparative embryology is often useful in determining homology
  • ultrastructure looks at fine details like cell structure, tissue organization and bone deposition
  • Behavioural - eg nesting behaviours and parental care
  • Genetic sequences - aligning homologous genes or proteins can show apomorphies like deletions,insertions,and substituted amino acids
• Dendrogram

  • means tree

  
• Phylogram

  • attempts to show variables other than branching pattern
  • Issues - variables are rarely stated, quantified or even justified
  • Artistic but not hard science

  
• Cladogram

  • throws away variables, except branching
  • branching is real, testable and ambiguous

  
• Ultrametric tree

  • follows cladistic principles
  • horizontal axis shows branching
  • vertical axis with empirical variable
  • Typically geological time and range of known fossils