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Cladistics
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History of Life Eras Boundaries between units in the Geologic Time Scale are marked by dramatic biotic change A figure from Ch. 26… 4500 Origin of Earth
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5 Kingdom classification system in use through the late 1900s
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5 Kingdom classification system in use through the late 1900s gave way to Woese’s 3 Domains
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5 Kingdom classification system in use through the late 1900s gave way to Woese’s 3 Domains and multiple Kingdoms
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“Did King Philip Come Over For Gumbo Sunday?”
Fig. 25.8 “Did King Philip Come Over For Gumbo Sunday?” Taxon (taxa) = the named taxonomic unit(s) at any level in this taxonomic hierarchy Each taxonomic level is more inclusive or comprehensive than the previous one (moving from species toward domains). Panthera = genus pardus = specific epithet that refers to one species in the genus Panthera
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Macroevolution & Phylogeny
Phylogenetic tree – hypothesized genealogy traced back to the last common ancestor (i.e., the most recent) through hierarchical, dichotomous branching Note that this is a highly pruned tree! Cladistics – the principles that guide the production of phylogenetic trees, a.k.a., cladograms
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Node – branch point, speciation event Note that this is a highly pruned tree!
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A paraphyletic group consists of an ancestor and some of its descendents
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Macroevolution & Phylogeny
Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A polyphyletic group lacks the common ancestor of species in the group
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Macroevolution & Phylogeny
Note that this is a highly pruned tree! Fig. 25.9 Taxonomic groups often reflect true clades…
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Macroevolution & Phylogeny
However, tension sometimes exists between taxonomic tradition and cladistic hypotheses… Note that phylogenetic trees can be oriented any which way.
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Macroevolution & Phylogeny
E.g., If the Class Reptilia is to be monophyletic, birds must be included!
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Macroevolution & Phylogeny
How are phylogenetic trees constructed?
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Cladistic Analysis Fossils provide morphological data for extinct species, whereas comparisons of multiple types of traits – including molecular – do so for extant species
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Ingroup = the group whose relationships we are trying to resolve
Cladistic Analysis Ingroup vs. Outgroup Ingroup = the group whose relationships we are trying to resolve Fig
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Cladistic Analysis Ingroup vs. Outgroup
Outgroup = a species (or group) known to have an older most recent common ancestor with the ingroup than the ingroup’s most recent common ancestor Fig
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Cladistic Analysis Ingroup vs. Outgroup
An outgroup helps identify shared ancestral and shared derived characters (unique to a clade) Fig
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Parsimony & Occam’s Razor
Cladistic Analysis Parsimony & Occam’s Razor The most parsimonious tree is the one that requires the fewest evolutionary events (appearance of shared derived characters) Fig
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Parsimony & Occam’s Razor
Cladistic Analysis Parsimony & Occam’s Razor On this most parsimonious cladogram, each key character originated (evolved) once Fig
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Cladistic Analysis An example… See Fig. 25.15 for another example
Outgroup Ingroup See Fig for another example
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Cladistic Analysis An example… See Fig. 25.15 for another example
Outgroup Ingroup Create potential topologies for the tree See Fig for another example
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Cladistic Analysis An example… See Fig. 25.15 for another example
Outgroup Ingroup Create potential topologies for the tree The first topology requires 7 changes, the second 9, and the third 8. Map the characters onto the trees Choose the most parsimonious tree See Fig for another example
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Macroevolution & Phylogeny
Sometimes the most parsimonious arrangement for one character is not the most accurate overall… Bird-mammal clade Lizard-bird clade Fig
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Macroevolution & Phylogeny
Don’t confuse the age of a clade with the age of its component species African Rift Lake Cichlid Alligator Snapping Turtle ~ 200,000 yr ~ 20,000,000 yr Based on the cladogram, which species is likely to be older? Once a clade arises, speciation events can continue to occur within it.
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Answer to Cladistics Homework
Lungfish Turtle Wolf Lamphrey Human Gorilla Pike Bony Shell Grasping Hand Hair Lung Jaw
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