BIOL1130 Lecture Notes - Lecture 3: Atavism, Ribosomal Rna, Chloroplast Dna
7 Jun 2018
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Discovering Evolutionary Relationships
• Understand that all life is connected through its evolutionary history
• Understand the concepts of phylogenetic analysis
• Appreciate parsimony as the guiding principle for inferring phylogeny
• Appreciate that phylogeny makes biology comparative and predictive
Phylogeny – the evolutionary history of a species
Phylogenetic tree – a diagrammatic representation of that history
Systematics – the field of biology concerned with studying phylogeny
Taxon – any group of species designated with a name
Clade – any taxon consisting of all the evolutionary descendants of a common
ancestor
Systematists – biologists who investigate phylogenies
• They use:
o Morphology – visible traits of an organism (anatomy, embryology)
o Fossil Record
o Molecular biology – molecules in an organism, proteins (amino
acid sequences), DNA and RNA (nucleotide sequences)
o Computers
How is a tree interpreted?
• A dot is a species, population or gene at one point in time
• A line becomes a lineage as we follow its descendants
• Traits are placed in specific places to show their timeline
o A fork in the tree shows the species diverging into different
lineages, ancestral lineage to two descendant lineages.
o Positions of nodes indicated the times of divergence events
Homologous Features
• Provide information for examining phylogeny
• Have evolved from a common ancestor
• May now have different functions
• Divergent Evolution
• Can be any heritable trait, including a protein, DNA sequence or even a
behavior
Derived traits provide evidence of evolutionary relationships
• Ancestral or primitive character – plesiomorphic
• Derived or advanced character – apomorphic
• Many apomorphic traits = synapomorphic
• Many Plesiomorphic traits = symplesiomorphic
Convergent evolution
• Not all traits are evidence of relatedness
• Similarity due to similar environments
o E.g. succulent plants inhabit arid areas (cacti, euphorbs, aloe)
• Similar in form but not evolutionary related
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Document Summary
Discovering evolutionary relationships: understand that all life is connected through its evolutionary history, understand the concepts of phylogenetic analysis, appreciate parsimony as the guiding principle for inferring phylogeny, appreciate that phylogeny makes biology comparative and predictive. Phylogeny the evolutionary history of a species. Phylogenetic tree a diagrammatic representation of that history. Systematics the field of biology concerned with studying phylogeny. Taxon any group of species designated with a name. Clade any taxon consisting of all the evolutionary descendants of a common ancestor. Systematists biologists who investigate phylogenies: they use, morphology visible traits of an organism (anatomy, embryology, molecular biology molecules in an organism, proteins (amino acid sequences), dna and rna (nucleotide sequences, fossil record, computers. Homologous features: provide information for examining phylogeny, have evolved from a common ancestor, may now have different functions, divergent evolution, can be any heritable trait, including a protein, dna sequence or even a behavior.
