Biology Classification & Taxonomy Flashcards Flashcards

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Taxonomy

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The science of naming, describing, and classifying organisms into groups based on shared characteristics. It provides a standardized framework for organizing biological diversity and communicating about species.

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Taxon

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A named group of organisms at any rank in the taxonomic hierarchy, such as species, genus, or family. A taxon represents a unit used by taxonomists to organize and study biodiversity.

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Taxonomic Rank

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A level in the hierarchical classification system (for example, domain, kingdom, phylum, class, order, family, genus, species). Each rank groups organisms by increasingly specific shared traits.

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Binomial Nomenclature

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The two-part scientific naming system for species consisting of a genus name followed by a specific epithet (for example, Homo sapiens). It ensures unique, universally accepted names for species.

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Linnaean System

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A hierarchical classification framework developed by Carl Linnaeus that organizes life into nested ranks such as kingdom, class, order, genus, and species. It laid the foundation for modern taxonomy though it has been updated with evolutionary concepts.

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Domain

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The highest taxonomic rank that groups life into major cell-based lineages: Bacteria, Archaea, and Eukarya. Domains reflect fundamental differences in cell structure, biochemistry, and genetics.

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Cladistics

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An approach to classification based on common ancestry and branching patterns of evolution, using shared derived characters (synapomorphies) to define clades. Cladistics aims to produce classifications that reflect evolutionary history.

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Phylogeny

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The evolutionary history and relationships among organisms or groups, often depicted as a tree showing branching lines of descent. Phylogenies are inferred using morphological and molecular data.

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Monophyletic

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A group (clade) that includes a common ancestor and all of its descendants. Monophyletic groups reflect true evolutionary lineages and are the preferred units in modern classification.

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Paraphyletic

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A group that includes a common ancestor and some, but not all, of its descendants. Paraphyletic groups omit one or more lineages that share the same ancestor, making them less accurate for representing evolutionary history.

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Polyphyletic

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A group composed of organisms that do not share an immediate common ancestor within the group, often grouped by convergent traits rather than common descent. Polyphyletic groups are not used for modern evolutionary classifications.

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Species Concept

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A general term for criteria used to define species; common types include the biological, morphological, and phylogenetic species concepts. Different concepts emphasize reproductive isolation, structural similarity, or shared ancestry respectively.

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Biological Species

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A species concept defining species as groups of interbreeding natural populations that are reproductively isolated from other such groups. It focuses on gene flow but is limited for asexual organisms and fossils.

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Type Specimen

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A physical example of an organism (holotype, lectotype, etc.) designated as the reference for the name of a species. Type specimens anchor species names to real samples stored in collections.

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Holotype

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The single specimen designated by the original author as the name-bearing specimen for a new species. The holotype is the primary reference for identification and future taxonomic work.

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Synonymy

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The situation in taxonomy where multiple names have been applied to the same taxon; synonyms are alternate names that are not the accepted name. Resolving synonymy ensures stability and reduces confusion in nomenclature.

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International Codes

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Sets of rules governing scientific names, such as the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants. These codes regulate naming, typification, and priority to maintain consistency.

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Molecular Systematics

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The use of DNA, RNA, and protein sequence data to infer evolutionary relationships and classify organisms. Molecular approaches often provide higher resolution for phylogenies than morphology alone.

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Dichotomous Key

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A stepwise identification tool that presents paired choices leading the user to the correct taxon based on observable characters. Dichotomous keys are practical aids for identifying species in the field or lab.

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Subspecies

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A taxonomic rank below species used for geographically or morphologically distinct populations that can still interbreed with other populations of the species. Subspecies designation recognizes notable variation without full species separation.