4.8 - Intro to Systematics

• Phylogeny


  The evolutionary history of a species or group of species.
• Systematics


  The study of the kinds and diversity of organisms and of any and all relationships among them.
• Homology


  Similarity due to shared ancestry.
• Molecular Clock


  A yardstick for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates.
• Systematics


  Tracing phylogeny is one of the goals systematics.

  Hence, it is considered as the study of biological diversity in an evolutionary context.

  Use data ranging from fossils to molecules and genes to infer evolutionary relationships.
• The Tree of Life

  A phylogenetic tree shows the evolutionary relationships among different organisms. The branches of the tree show where genetic or physical similarities and differences between organisms begin and end.

  A phylogenetic tree is like a family tree. The root of the tree represents a distant ancestor of the species that appear at the ends of the branches. The branches separate at nodes, or points where ancestral lines split into new lines of evolution.
• Lines of Evidence to Infer Evolutionary Relationships

  • Fossil Evidence
  • Homologies
  • Developmental Biology
  • Biogeography
  • Molecular Clocks Help Track Evolutionary Time
• Homologies


  Similar characters due to relatedness.

  Can be revealed by comparing the anatomies of different living things, looking at cellular similarities and differences, studying embryological development, and studying vestigial structures within individual organisms.
• Developmental Biology


  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


  The geographic distribution of species in time and space as influenced by many factors, including Continental Drift and long-distance dispersal.
• Purpose of Using Phylogenetic Trees

  • Testing hypotheses about the evolution
  • Learning about the characteristics of extinct species and ancestral lineage
  • Classifying organisms