M13 BIO

Module 13: Phylogenies and History of Life

• Organizing Life on Earth

• Phylogeny: Evolutionary history of species.
  
  

• Phylogenetic Tree:
  
  

  • Rooted: Common ancestor shown.
    
    

  • Unrooted: No direction.
    
    

• Key Terms:
  
  

  • Branch Point: Split into two lineages.
    
    

  • Basal Taxon: Early lineage.
    
    

  • Sister Taxa: Closest relatives.
    
    

  • Polytomy: Unresolved branch split.
    
    

• Systematics: Study of relationships.
  
  

• Taxonomy: Naming and classifying (Domain → Species).

• Determining Evolutionary Relationships

• Homologous Traits: From a common ancestor.
  
  

• Analogous Traits: Similar but evolved separately (convergent evolution).
  
  

• Molecular Systematics: DNA/RNA/protein used to build trees.
  
  

• Cladistics:
  
  

  • Groups based on common ancestry (clades).
    
    

  • Shared derived characters distinguish clades.
    
    

• Maximum Parsimony: Simplest explanation is preferred.
  
  

• Perspectives on Phylogenetic Trees

• Horizontal Gene Transfer (HGT): Genes move between unrelated species.
  
  

  • Common in prokaryotes (transformation, conjugation, etc.)
    
    

• Genome Fusion & Endosymbiosis:
  
  

  • Mitochondria and chloroplasts originated from engulfed bacteria.
    
    

• Alternative Evolution Models:
  
  

  • Web of Life, Ring of Life, Ficus Tree Analogy.
    
    

• Reading a Phylogenetic Tree

• Root: Common ancestor.
  
  

• Branch: Lineage over time.
  
  

• Node: Last common ancestor.
  
  

• Tip: Current species/group.
  
  

• Monophyletic Group: Ancestor and all descendants (clade).
  
  

• Synapomorphy: Shared derived trait.
  
  

• Homoplasy: Same trait evolved independently.