Overview on Phylogenetics

Ontogeny
  • individual growth and development of an organism
  • occurring from early to later stages of development of an individual
  • recapitulation theory   * morphological changes occurring in the embryo
Phylogeny
  • evolutionary history and relationships of a species
  • morphological or molecular changes that occurred in the species’ lineage   * sequence of descent from an ancestor
  • shows hypothetical evolutionary relationships among different species in the form of a phylogenetic tree

Laws to summarize patterns of embryonic development

von Baer’s Law
  • development of an organism starts from general features into more specific features
  • one species’ embryonic forms are very different from another species’ adult forms
  • developmental stages of organisms like mammals do not embody the adult stages of animals like amphibians/reptiles, only resemblance to their embryonic forms
Biogenetic Law (Recapitulation Theory)
  • proposed by Ernst Haeckel in 1866
  • “ontogeny recapitulates phylogeny”
  • proposes that the development of an organism (ontogeny) recapitulates its evolutionary history (phylogeny).
  • suggests that the stages of embryonic development in an organism mirror the evolutionary stages of its ancestors
  • has been discredited in modern biology as an oversimplification

Phylogenetics

Significance
  • serve as critical tools for the study of evolutionary history and relationships
  • offers approaches to examining nature, inquiring and addressing issues related to the evolution of organisms
  • continuously grows and changes in response to new information

Relationship to other disciplines

Comparative biology
  • studying the characteristics of diverse organisms to infer evolutionary relationships
Systematics
  • organizing and classifying species based on evolutionary relationships
  • integrates information from phylogeny which uses data from various sources such as fossils, body structures, or molecules the organism uses, and DNA analysis
Taxonomy
  • naming of organisms using binomial nomenclature
  • classification of organisms using the Linnaean System is based on morphological features
  • hierarchical categorization of organisms

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