Ch 26 - Phylogeny and the tree of life (1 slide per page)-2

G all mammals have a vertebral column but so do other

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Unformatted text preview: column but so do other groups • Shared derived traits DO give a monophyletic group e.g. all mammals have hair but not other groups 60 60 A shared ancestral trait for 1 group may be a shared derived trait for another group Fish Vertebrates Mammals e.g. Vertebral column is a shared ancestral trait for mammals but a shared derived trait for vertebrates (FYI - A shared derived trait is also known as a “synapomorphy”) 62 62 Shared derived characters are used to construct phylogenetic trees Chordata Arthropoda Animalia Angiosperms Plantae Eukarya Taxonomy = Phylogeny 63 63 Trees are Hypotheses A phylogenetic tree is a hypothesis about evolutionary history & relationships. • As always, must test hypotheses: - look for concordance between many lines of evidence Mosses Flowering plants Conifers Ferns C B A 65 65 Based on data several trees may be possible Figure 26.15 Campbell et al (9th ed) 66 66 Principle of parsimony allows us to arrive at the most likely scenario • Only some of these groups have legs • What different ways could this pattern could have arisen? – Legs – Legs + Legs MRCA w/o legs 67 67 Principle of parsimony allows us to arrive at the most likely scenario • Only some of these groups have legs • What different ways could this pattern could have arisen? – Legs – Legs + Legs –...
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