Systematics

• Systematics 


  Study of the diversity of life forms and the evolutionary relationships of organisms
• Systematics

  • Systematists use data from fossils to molecules to genes to infer evolutionary relationships and reconstruct the Tree of Life
• Cladogram


  Shows evolutionary relationships of organisms
• Phylogeny


  Evolutionary history of a species or a group of species
• Phylogenetic Tree


  An extensive and more detailed cladogram
• Systematics is the study of the kinds and diversity of organisms and of any and all relationships among them
• Tracing phylogeny is one of the goals of systematics; hence, it is considered as the study of biological diversity in an evolutionary context
• Systematists use data ranging from fossils to molecules and genes to infer evolutionary relationships
• These information enable biologists to construct a comprehensive tree of life that will continue to be refined as additional data are collected
• The Tree of Life is a model and a phylogenetic tree that shows the evolutionary relationships of all organisms, backed by evidences, from fossil, behavioral, molecular, and morphological data
• Lines of evidence to infer evolutionary relationships

  1. Fossil evidence

  2. Homologies
• Homologies

  Similar characters due to relatedness are known as homologies
• Homologies can be revealed by comparing the anatomies of different living things, looking at cellular similarities
• Taxonomy is the science that deals with classification, naming, and identification of organisms
• Classification - grouping of organisms into categories based on similarities and differences
• Nomenclature - assigning names to taxa (groups) according to rules
• Lines of evidence to infer evolutionary relationships

  • Fossil evidence
  • Homologies
  • Molecular homology
  • Developmental biology
  • Biogeography
  • Molecular clocks
  • Classification linked to phylogeny
• Similar characters due to relatedness are known as homologies
• Ways to reveal homologies


  • Comparing the anatomies of different living things
  • Looking at cellular similarities and differences
  • Studying embryological development
  • Studying vestigial structures within individual organisms
• Molecular comparisons may reveal mutations
• Measuring the degree of similarities in a molecular level can be achieved by the latest software technologies, while physically, some differences can be unnoticeable
• Studying the embryological development of living things provides clues to the evolution of present-day organisms
• During some stages of development, organisms exhibit ancestral features in whole or incomplete form
• Biogeography involves the geographic distribution of species in time and space as influenced by factors such as Continental Drift and long-distance dispersal
• Molecular clocks help track evolutionary time
• The base sequences of some regions of DNA change at a rate consistent enough to allow dating of episodes in past evolution
• Other genes change in a less predictable way
• The connection between classification and phylogeny is that hierarchical classification is reflected in the progressively finer branching of phylogenetic trees
• The branching patterns in some cases match the hierarchical classification of groups nested within more inclusive groups
• In some situations, certain similarities among organisms may lead taxonomists to place a species within a group of organisms other than the group to which it is closely related
• Biologists care about phylogenies because species' phylogeny provides an enormous amount of information
• Identification - determining which species or higher category a particular specimen belongs to
• Classifying living things involves identifying their characteristics and placing them into categories based on those characteristics