Ch12: Systematics: The Science Of Biological Diversity

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Eukarya

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The phylogenetic domain containing all eukaryotic organisms

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clade

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A monophyletic group, made up of an ancestor and all of its descendants

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category

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[Gk. kat goria, category] In a hierarchical classification system, the level at which a particular group is ranked

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sporophyte

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The spore-producing, diploid (2n) phase in a life cycle characterized by alternation of generations

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taxonomy

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[Gk. taxis, arrangement, + nomos, law] The science of the classification of organisms

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specific epithet

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The second part of a species name; for example, mays of Zea mays (maize)

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cladogram

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A line diagram that branches repeatedly and suggests phylogenetic relationships among organisms

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synapomorphies

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Character states (two or more forms of a character) that arose in the common ancestor of a group and are present in all of its members

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alternation of generations

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A reproductive cycle in which a haploid (n) phase, the gametophyte, produces gametes, which fuse in pairs to form a zygote, which then germinates to produce a diploid (2n) phase, the sporophyte. Spores produced by meiotic division in the sporophyte give rise to new gametophytes, completing the cycle

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gametophyte

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In plants that have an alternation of generations, the haploid (n), gamete-producing generation, or phase

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outgroup

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In a cladogram, a species or group of species that does not exhibit one or more shared derived characters found in the group under study, the ingroup

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phylogeny

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[Gk. phylon, race, tribe] Evolutionary relationships among organisms; the developmental history of a group of organisms

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cladistics

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A system of arranging organisms following an analysis of their primitive and advanced features so that their phylogenetic relationships are accurately reflected

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analogous

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[Gk. analogos, proportionate] Applied to structures similar in function but different in evolutionary origin, such as the phyllodes of an Australian Acacia and the leaves of an oak

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convergent evolution

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[L. convergere, to turn together] The independent development of similar structures in organisms that are not directly related; often found in organisms living in similar environments

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isomorphic

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[Gk. isos, equal, + morph, form] Identical in form

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heteromorphic

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[Gk. heteros, different, + morph, form] Describing a life history in which the haploid and diploid generations are dissimilar in form

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systematics

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Scientific study of the kinds and diversity of organisms and of the relationships between them

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taxon

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General term for any one of the taxonomic categories, such as species, class, order, or phylum