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Phylogenetic Trees and Systematics

  • Phylogeny: Evolutionary history and relationships among organisms, represented as phylogenetic trees.
  • Phylogenetic Tree Structure:
    • Node: Point where a lineage splits; represents an ancestor.
    • Branch: Line that connects nodes, showing relationships.
    • Most Recent Common Ancestor (MRCA): The youngest common ancestor for a group; shown at node intersections.
  • Comparison of Relationships: Determines closeness between taxa by the depth of their MRCA; shallower MRCA indicates closer relation.
  • Estimating Phylogenies: Uses character similarities to differentiate taxa into homology (common ancestry) and analogy (convergent evolution).
  • Characters: Traits used to group organisms. Can be classified as ancestral (older) or derived (newer).
  • Molecular Systematics: Utilizes DNA sequence data for phylogenetic studies.
  • Horizontal Gene Transfer (HGT): Transfer of genes across different species complicating evolutionary relationships.