BIO152H5 Chapter Notes - Chapter 27: Paleogene, Radiometric Dating, Cambrian Explosion

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Chapter 27- phylogenies and the history of life. Phylogeny: evolutionary history of a group of organisms. Phylogenetic tree: shows ancestor-descendant relationships among populations or species, and clarifies who is related to whom. Phylogenetic trees are an extremely effective way of summarizing data on the evolutionary history of a group of organisms. Phenetic approach: computing a statistic that summarizes the overall similarity among populations based on data. Gene sequences used to compute an overall genetic distance. Cladistic approach: relationships among species can be reconstructed by identifying shared derived characters, or synapomorphies, in the species being studied. Synapomorphy- a trait that certain groups of organisms have that exists in no others. Allow biologists to recognize monophyletic groups- called clades or lineages. Fur and lactation are synapomorphies that identify mammals. Traits can be similar in 2 species not because they were present in common ancestor but because similar traits evolved independently in two distantly related groups.

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