Chapter 7

• Systematics or taxonomy.• Study of the kinds and diversity of organisms and ofthe evolutionary relationships among them
• Phylogeny.• Gr. phylon, race + geneia, origin.• A description of the evolutionary history of a group oforganisms and is usually depicted using tree diagrams.
• Taxon.• Any grouping of animals that shares a particular set ofcharacteristics
• Taxonomic categories.• Hierarchically arranged (broader to specific).• Domain, kingdom, phylum, class, order, family, genus,species.• As one moves down through the hierarchy from domaintoward species, one is looking at groups derived from morerecent ancestors and a smaller subset of more closelyrelated animals.
• International Code of Zoological Nomenclature.• No two animals have the same binomial.• Every animal has only one correct name.• The genus of an animal begins with a capital letter, thespecies epithet begins with a lowercase letter, and theentire scientific name is italicized or underlined because itis derived from Latin or is latinized
• Relatedness of animals reflected in proteins andDNA.• Nuclear and mitochondrial DNA.• Ribosomal RNA.
• Ribosomal RNA studies.• Distant evolutionary relationships.• Evolutionary conservation results in very slow rates of change (evolutionaryconservation
• Animals also have extragenic DNA that does not code for protein.• Comprises a large portion of animal genomes.• Can change without harming the animal, not conserved evolutionarily.• A number of DNA analysis techniques (e.g., microsatellites and amplified fragmentlength polymorphisms [AFLP]) can be used to examine this DNA and investigatephylogenetic changes
• Analysis tools are used to study base sequences, identify the correspondinggenes, and compare these genes to other base sequences in molecular databases.• A commonly used database is maintained by the National Center for Biotechnology Information (NCBI)
• Animal Systematics Goal.• Arrange animals into groups that reflect evolutionaryrelationships
• Single ancestral species and all descendants.• monophyletic group.
• Polyphyletic groups – do not include the most recent commonancestor of all members of the group
• Paraphyletic groups – include some, but not all, descendants ofa most recent common ancestor.
• Symplesiomorphy – a shared ancestral character among a group oforganisms.• Cannot be used to describe relationships within the groupbecause present in all members
• Outgroup.• Related group not included in study group.• Used to help decide whether a character is ancestral or has morerecently derived
• Characters that are unique or have arisen since commonancestry with the outgroup are called derived character statesor apomorphies
• Derived characters shared by members of a group are called synapomorphies
• Cladogram.• Depicts a sequence in the origin of derived character states
• Clade.• Related subset within a lineage or cladogram.
• Hierarchical nesting.• Cladograms represent nested groups that share synapomorphiccharacters.• The less inclusive the nest is, the more closely related the organisms.
• A second approach to animal systematics is called evolutionary systematics
• Phylogenetic trees depict relationships, time, andabundance
• Phylogenetic species concept.• Allows one to define species based on commonphylogenetic history.• Smallest diagnosable monophyletic group ofpopulations within which there is a parental pattern ofancestry and descent.• Distinguished from other groups by one or moresynapomorphies common to the species.
• Asymmetry – the absence of a central point or axisaround which body parts are equally distributed
• Radial symmetry – the arrangement of body parts suchthat any plane passing through the central oral-aboralaxis divides the animal into mirror images
• Bilateral symmetry – the arrangement of body parts suchthat a single plane, passing between the upper and lowersurfaces and through the longitudinal axis of an animal,divides the animal into right and left mirror images.
• Aboral The end opposite the mouth of a radially symmetrical animal.
• Oral the end containing the mouth of a radially symmetrical animal
• Anterior The head end: usually the end of a bilateral animal that meets itsenvironment.
• Posterior The tail end.
• Caudal Toward the tail
• Cephalic Toward the head.
• Distal Away from the point of attachment of a structure on the body (e.g.. thetoes are distal to the knee).
• Proximal Toward the point of attachment of a structureon the body (e.g.. the hip is proximal to the knee).29
• Dorsal The back of an animal: usually the upper surface:synonymous with posterior for animals that walk upright
• Ventral The belly of an animal: usually the lower surface:synonymous with anterior for animals that walk upright
• Inferior Below a point of reference (e.g., the mouth is inferior to thenose in humans)
• Superior Above a point of reference (e.g.. the neck is superior to thechest)
• Lateral Away from the plane that divides a bilateral animal intomirror images.
• Medial (median) On or near the plane that divides a bilateral animal intomirror images.