Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 22 Understanding Diversity: Systematics

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Systematics Diversity of organisms Evolutionary relationships Biodiversity –The variety of organisms –The ecosystems they form

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Taxonomy Naming Describing Classifying Classification Grouping organisms by their similarities or relationships

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Binomial nomenclature Genus + specific epithet –Homo sapiens –Quercus alba Linnaeus, mid-18 th century Facilitates international science

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Taxonomic categories Kingdom Phylum Class Order Family Genus Species

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Taxonomic Categories

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Six Kingdoms Based on cell structure & nutrition Archaebacteria Eubacteria Protista Fungi Plantae Animalia

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Six Kingdoms

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Three domains Based on molecular differences Archae –Lack simple RNA polymerase Eubacteria –Peptidoglycan in cell walls Eukarya –Eukaryotes

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Three Domains

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Phylogeny Evolutionary history of a group of organisms from a common ancestor Classifications based on common ancestors Traditionally based on structural similarities

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Homology Structure derived from a recent common ancestor –Wing bones in birds and bats Homoplasy –Superficially homologous but independently acquired Body form in sharks and dolphins

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Plesiomorphic characters Shared ancestral characters Distant common ancestor Synapomorphic characters Shared derived characters More recent common ancestor

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Molecular systematics Determines evolutionary relationships by comparing macromolecules Ribosomal RNAs 5S, 16S, 23S –Transcribed from highly conserved DNA regions Mitochondrial DNA

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Molecular taxonomy

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Molecular clocks Measure time since divergence from a common ancestor by the number of differences in nucleotide or protein sequences Rate of change must be constant

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Monophyletic taxon All descendants of most recent common ancestor –Mammals True evolutionary relationships Clade

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Paraphyletic taxon Common ancestor but not all descendants –Class Reptilia does not include birds even though they share a recent common ancestor Avoided by cladistic systematists

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Monophyletic and paraphyletic taxa

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Polyphyletic group Does not share recent common ancestors –Protista Shares homoplastic features Misrepresents evolutionary relationships

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Polyphyletic groups

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Evolutionary systematics Evolutionary branching Extent of divergence –Structural and other changes Combination of shared ancestral characters and shared derived characters

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Evolutionary systematics

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Cladistics

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Cladistics Emphasizes common ancestry over phenotypic similarity Only shared derived characters Cladograms Parsimony guides choices

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Using parsimony to evaluate hypotheses

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 22 Understanding Diversity: Systematics Outgroup analysis Separate ancestral and derived characters Outgroup taxon diverged earlier than others Outgroup represents the ancestral condition