BIOL 1111 Lecture Notes - Lecture 4: Phylogenetic Tree, Phylocode, Evolutionary Taxonomy
13 Jun 2018
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Converting a phylogenetic tree into classification
Use the Principle of Monophyly (group organisms based on common evolutionary ancestry)
1. Monophyletic taxa
-includes one single ancestral species and all its descendants
2. Polyphyletic taxa
-includes species from separate evolutionary lineages
-not intentionally used in systematics
-groups of organisms together based on characteristics, not based on evolution
-ex. Flying animals
3. Paraphyletic taxa
-contains an ancestor and some but NOT ALL descendants
-ex. Reptilia (not proper grouping always)
Parsimony
Principle of parsimony
-fewest possible evolutionary changes to account for diversity within a lineage (simplest explanations is
most likely correct)
-assumes that evolutionary change is an unlikely event, and therefore evolution of a character twice in a
lineage is extremely unlikely
-evolutionary trees with derived characters appearing once are most parsimonious
Traditional vs. Cladistic Systematics
1. Traditional evolutionary systematics
-use phenotypic similarities and differences to infer evolutionary relationships
-based on body plans and ways of life; ancestral and derived traits differentiated the
organisms
-Problem: classes may not always include all descendants of a common ancestor
2. Cladistics
-uses only evolutionary relationships
-groups all species that share derived characters
Clade: monophyletic lineage
Cladograms: tree made of clades
Phylocode: cladistics system to identify and name clades
-common ancestor; each node represents most recent ancestor and what derived trait
divides them
Parallelism and Convergence
Parallelism: closely related organisms that evolve similar characteristics because living under similar
environmental conditions
Convergence: same but for distantly related species
-look at morphology, embryology, behaviour, molecular data and more to compare
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Use the principle of monophyly (group organisms based on common evolutionary ancestry: monophyletic taxa. Includes one single ancestral species and all its descendants: polyphyletic taxa. Groups of organisms together based on characteristics, not based on evolution. Contains an ancestor and some but not all descendants. Fewest possible evolutionary changes to account for diversity within a lineage (simplest explanations is most likely correct) Assumes that evolutionary change is an unlikely event, and therefore evolution of a character twice in a lineage is extremely unlikely. Evolutionary trees with derived characters appearing once are most parsimonious. Traditional vs. cladistic systematics: traditional evolutionary systematics. Use phenotypic similarities and differences to infer evolutionary relationships. Based on body plans and ways of life; ancestral and derived traits differentiated the organisms. Problem: classes may not always include all descendants of a common ancestor: cladistics. Phylocode: cladistics system to identify and name clades. Common ancestor; each node represents most recent ancestor and what derived trait divides them.
