Topic 2-Taxonomy & Systematics

• Monophyletic is a taxon in which all species share a most recent common ancestor, and all species derived from that common ancestor must be included.
• Systematists compare each ingroup species with the outgroup to differentiate between synapomorphic and symplesiomorphic character states.
• Polyphyletic is the derivation of a taxon from two or more ancestral sources.
• Paraphyletic is a taxon in which all species share a most recent common ancestor, but not all species derived from that common ancestor are included.
• An outgroup is a species or group of species that is closely related to the ingroup, the various species being studied, and the outgroup is a group that has diverged before the ingroup.
• Character states can be primitive (= plesiomorphic) or derived (= advanced/apomorphic).
• Plesiomorphic characters are the earliest original character states that gave rise to derived states.
• Symplesiomorphy: Character state is primitive, therefore old. Present in more than one taxa.
• Cladistic classification is a type of systematics that is based on cladograms.
• systematics is the study of biodiversity
• Systematics studies and establishes phylogenies
• Phylogeny: The evolutionary history of a group of organisms.
• Homology: Similarities (in terms of skeletal structure) due to ancestry. Can have no resemblance to one another in location, appearance, or function.
• Analogy/homoplasy: Similarity between structures that is NOT due to a recent common ancestor.
• Ex. of homology: Human, cat, whale, bat; all of which orginated from the same common ancestor. The forelimbs are constructed from the same basic skeletal structures.
• Analogous structures result from convergent evolution, where two or more species are in similar environments and develop similar structures to perform similar functions.
• Homoplasy(homoplastic): Similar in appearance but not origin.
• Phylogeny: evolutionary history of organisms
• Principle of parsimony: The simplest is correct. Choose tree with fewer evolutionary events.
• Taxonomy consists of genus and species name.
• Nomenclature is a system of names or terms that are used to identify organisms.
• Phylogenetic trees consist of clades (lineage that emerge from node)
• Taxonomic categories: Domain, kingdom, phylum, class, order, family, genus, species.
• Same terms: Primitive=plesiomorphic=symplesiomorphy
• Same terms: Derived=advanced=apomorphic=apomorphy
• Sister group: 2 taxas that share history
• Branch: can represent time
• Taxon/taxa(pleural): A group of one or more populations of an organism.
• Monophyletic: All species share a most recent common ancestor, & all species derived from that common ancestor must be included.
• Polyphyletic: A group of organisms that are not closely related to each other. Derived.
• Paraphyletic: species share a most recent common ancestor, but not all species derived from that common ancestor are included.
• Ingroup: Species you are studying
• Outgroup: Closest relative to ingroup. Distantly related organism.
• Synapomorphy: Characteristic unique to a clade; derived characteristic.
• Same terms: Derived=advanced=apomorphic=synapomorphy