Chapter 7. Animal Classification, Phylogeny, and Organization. Classification of Organisms. Systematics or taxonomy Study of the kinds and diversity of organisms and of the evolutionary relationships among them. A Taxonomic Hierarchy. Taxon
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Chapter 7 Animal Classification, Phylogeny, and Organization
Classification of Organisms • Systematics or taxonomy • Study of the kinds and diversity of organisms and of the evolutionary relationships among them
A Taxonomic Hierarchy • Taxon • Any grouping of animals that shares a particular set of characteristics • Taxonomic categories • Hierarchically arranged (broader to specific) • Domain, kingdom, phylum, class, order, family, genus, species • Above species level there are no definitions for each category
Nomenclature • Binomial system of nomenclature • International Code of Zoological Nomenclature • Homo sapiens (H. sapiens) • Other naming rules • See General Zoology Laboratory Manual (Exercise 6).
Molecular Approaches to Animal Systematics • Relatedness of animals reflected in proteins and DNA. • Nuclear and mitochondrial DNA • Ribosomal RNA
Domains and Kingdoms • Ribosomal RNA studies • Distant evolutionary relationships • Evolutionary conservation results in slow rates of change. • Three major lineages (Domains) • Eubacteria • Bacteria • Archaea • Extremophile microbes • Eukarya • Organisms with compartmentalized cells • Nuclear membranes mitochondrial and chloroplast membranes • Horizontal gene transfer (HGT) common in early history of life and makes base of tree net-like
Animal Systematics • Goal • Arrange animals into MONOPHYLETIC GROUPS using traits having a genetic basis and that can be measured (characters). • Single ancestral species and all descendants • Groupings reflecting insufficient knowledge • Members of a lineage found to have separate ancestry • Polyphyletic groups • Some, but not all, members of a lineage included • Paraphyletic group
Approaches to Animal Systematics • Evolutionary systematics • Traditional approach • Homologies useful in classification • Phylogenetic trees depict relationships, time, and abundance.
Approaches to Animal Systematics • Phylogenetic systematics (cladistics) • Homologies of recent origin are most useful. • Ancestral characters • Common to all members of a group • Symplesiomorphies • Outgroup • Related group not included in study group • Used to help decide whether or not a character is ancestral or more recently derived
Approaches to Animal Systematics • Phylogenetic systematics (continued) • Derived characters • Arisen since common ancestry with the outgroup • Synapomorphies • Clade • Related subset within a lineage • Cladogram • Depicts a hypothesis regarding monophyletic lineage
Figure 7.5 This hypothetical cladogram shows five taxa (1-5) and characters (A-H) used in deriving taxonomic relationships.
Approaches to Animal Systematics • Phylogenetic species concept • Group of populations that have evolved independently of other groups of populations • Monophyletic • Share one or more synapomorphies • Hierarchical nesting • Cladograms represent nested groups that share synapomorphic characters. • Less inclusive nests contain closely related organisms.
Compare figures 7.4 and 7.6 • What kind of information is common to both representations? • What kind of information is present in figure 7.4 that is not in figure 7.6? • What kind of information is present in figure 7.6 that is not in figure 7.4? • How are the relationships between reptiles, birds, and mammals represented differently in the two figures? • How do the differences in question 4 reflect differing approaches of evolutionary systematics and phylogenetic systematics?
Table 7.2 • Symmetry describes how parts of an animal are arranged around a point or axis.
Figure 7.7 Sponges display cell-aggregate organization and some sponges are asymmetrical (Monochora barbadensis).
Figure 7.9 Bilateral symmetry is accompanied by the formation of a distinct head (cephalization).
Other Patterns of Organization • Unicellular (cytoplasmic) level of organization • Protists (unicellular) • Sponges (cell aggregate) • Diploblastic organization • Ectoderm (outer cellular layer) • Endoderm (inner cellular layer) • Mesoglea (noncellular)
Other Patterns of Organization • Triploblastic Organization • Mesoderm • Third tissue later sandwiched between ectoderm and endoderm • Supportive, contractile, and blood cells • Body cavities often present • Organ development • Exchanges by diffusion • Storage • Hydrostatic skeletons • Elimination of wastes and reproductive products • Facilitate increased body size
Figure 7.11 Triploblastic Organization. • Triploblastic acoelomate • Mesoderm forms solid mass. • Triploblastic pseudocoelomate • Body cavity not entirely lined by mesoderm. • Gut is not associated with muscle or connective tissue. • Triploblastic coelomate • Body cavity completely surrounded by mesoderm. • Mesenteries suspend visceral structures in body cavity.
Higher Animal Taxonomy • Animalia is monophyletic • Molecular and embryological evidence • Four phyla originated independently • Bilaterally symmetrical phyla • Protostome phyla • Spiral, determinate cleavage • Trochophore larval stage • Ecdysozoa • Molt a cuticle • Lophotrochozoa • Deuterostome phyla • Radial, indeterminate cleavage
Figure 7.13 Developmental characteristics of protostomes and deuterostomes.