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What are the Common Body Patterns and
Components in Animals?
• Grades of Organization: protoplasmic (protozoans), cellular
(metazoans, incl. sponges), cell-tissue (eumetazoans, incl.
cnidarians), tissue-organ (flatworms), and organ-system (others)
• Symmetry: asymmetrical (sponges), spherical (some protozoans),
radial (cnidarians), biradial (ctenophores), pentameral (echinoderms), bilateral (others; w/ cephalization: differentiation of a head)
– Bilateral Planes: sagittal, transverse (cross-section), and frontal planes
• Morphological Terms: anterior/posterior, dorsal/ventral, medial/lateral,
proximal/distal, pectoral, pelvic; oral/aboral (radial forms)
• Body Cavities: Acoelomate: mesoderm fills blastocoel; Pseudocoelomate: mesoderm lines outer edge of blastocoel; Coelomate:
body cavity lined entirely with mesoderm (peritoneum); true coelom
formed via schizocoelous or enterocoelous development
• Complete Gut Design and Segmentation: complete (one-way) gut
allows efficient digestion; segmentation allows greater mobility
• Components of Metazoan Bodies: epithelial, connective, muscular,
and nervous tissues
Table 9.1
Fig. 9.1
Fig. 9.2
Fig. 9.3
Figures 9.4 and 9.5
Fig. 9.6
Fig. 9.7
What is the Linnaean System of Taxonomy?
• Levels of taxonomy: Kingdom, Phylum (or Division); Class;
Order; Family; Genus and Species
– Today, all levels are intended to reflect evolutionary relatedness
– Developed by Carolus Linnaeus (mid 1700s), a Swedish botanist
• Binomial Nomenclature (Linnaeus, 1758)
– Each species receives a unique scientific name in Latin (common names
differ by location and change over time)
• Latin is a dead language (will not change), and is used internationally
– Scientific names always two words (Genus species), always underlined or
italicized (versus longer description in Latin); second name not used alone,
lower case, often describes location species found or in honor of person
• Tomato (pre-Linnaeus): Solanum caule inermi herbaceo, foliis pinnatis incises
• Descriptions of Newly Discovered Species
– Often identified based on their physical structure (Morphological Species
Concept); taxonomists attempt to include genetic comparisons and
ecological descriptions also (e.g., habitat)
– Holotype and Paratypes: first known specimen and subsequent specimens
described in peer-reviewed scientific journal
Table 10.1
Figures 10.2 and 10.3
How are Phylogenetic Relationships
Determined?
• Clade: an ancestral species and all of its descendents (a
“branch on the Tree of Life”)
– Cladistics: systematic analysis of clades and their relationships to
other clades; focuses on the evolutionary innovations that define
branch points in evolution (synapomorphies: shared, derived traits)
• Parsimony: convergence considered more rare than homology; tree that
results in fewest number of steps considered most parsimonious
• Techniques
– Often heavy computer memory requirements for statistical tests
(bootstrapping, Monte Carlo simulations, tests of monophyly)
• If multiple trees result with equal significance, relationships remain
unresolved (a “bush”)
• Any single resulting tree still considered a hypothesis; best if consistent
with other independent evidence (e.g., the fossil record)
– Character states entered for multiple traits (ex. horns present = 1,
horns absent = 0); taxa that share more homologies considered
more closely related; nucleotide or amino acid sequences often
used (eliminates potential bias in choice of characters)
Fig. 10.4
Fig. 10.11
Fig. 10.6