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ANT 301 (31)
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Chapter 5

Chapter 5 Notes

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University of Texas at Austin
ANT 301

1 Chapter 5 Macroevolution: Processes of Vertebrate and Mammalian Evolution Classification- in biology, the ordering of organisms into categories, such as orders, families, and genera, to show evolutionary relationships Chordata- the phylum of the animal kingdom that includes vertebrates Vertebrates- animals with segmented, bony spinal columns; includes fishes, amphibians, reptiles (including birds), and mammals Like a musical score with a basic theme, small variations on the pattern can produce the different “tunes” that differentiate one organism from another. This is the essential genetic foundation for most macro-evolutionary change Homologies- similarities between organisms based on descent from a common ancestor Analogies- similarities between organisms based strictly on common function with no assumed common evolutionary descent Homoplasy- the separate evolutionary development of similar characteristics in different groups of organisms 2 MAJORAPPROACHES OR “SCHOOLS” FOR CLASSIFICATION - Evolutionary systematics: a traditional approach to classification and evolutionary interpretation in which presumed ancestors and descendants are traced in time by analysis of homologous characters - Cladistics: an approach to classification that attempts to make rigorous evolutionary interpretations based solely on analysis of certain types of homologous characters (those considered to be derived characters) SIMILARITIES - Both are interested in tracing evolutionary relationships and in constructing classifications that reflect these relationships - Both recognize that organisms must be compared using specific features and that some of these characters are more informative than others - Both focus exclusive on homologies DIFFERENCES - In how characters are chosen - In which groups are compared - How the results are interpreted and eventually incorporated into evolutionary schemes and classifications Primary difference: cladistics more explicitly and more rigorously defines the kinds of homologies that yield the most useful information 2 Ancestral- referring to characters inherited by a group of organisms from a remote ancestor and thus not diagnostic of groups (lineages) that diverged after the character first appeared; also called primitive Clade- a group of organisms sharing a common ancestor; the group includes the common ancestor and all descendants Derived (modified) - referring to characters that are modified from the ancestral condition and thus diagnostic of particular evolutionary lineages Theropods- small to medium sized ground living dinosaurs dated to approximately 150 mya and thought to be related to birds Strict cladistics analysis assumes that Homoplasy is not a common occurrence; if it were, perhaps no evolutionary interpretation could be very straightforward Shared derived- relating to specific traits shared in common between two life-forms and considered the most useful for making evolutionary interpretations Phylogenetic tree- a chart showing evolutionary relationships as determined by evolutionary systematics; it contains a time component and implies ancestor descendant relationships Cladogram- a chart showing evolutionary relationships as determined by cladistics analysis; it’s based solely on interpretation of shared derived characters; it contains no time component and doesn’t imply ancestor-descendant relationships Biological species concept- a depiction of species as groups of individuals capa
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