Domains and Kingdoms

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Taxonomy Noun

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[tak-son-uh-mee]

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Taxonomy

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The biological science dedicated to naming, describing, and classifying all living organisms into a universally shared, hierarchical system.

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Example: This diagram shows taxonomy, the science of classifying living things, as a hierarchy from the most general group (Life) to the most specific (Species).

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Taxon Noun

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[tak-son]

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Taxon

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Any specific group or rank in a biological classification system, such as a species, family, or class of organisms.

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Example: This diagram shows the main levels of biological classification, from the broad 'Domain' to the specific 'Species'. Each level, such as Kingdom or Family, is a 'taxon'.

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Binomial nomenclature Noun

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[bahy-noh-mee-uhl noh-muhn-kley-cher]

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Binomial nomenclature

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The formal system of naming species whereby each name is composed of two parts, the genus and the species.

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Example: This diagram shows that binomial nomenclature is a two-part naming system, breaking down the tiger's scientific name (*Panthera tigris*) into its Genus and Species.

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Genus Noun

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[jee-nuhs]

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Genus

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A principal taxonomic rank that includes one or more physically similar species that are considered to be closely related.

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Example: This diagram shows the levels of biological classification for humans, placing Genus (Homo) as a more specific group than Family and a broader group than Species.

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Phylogeny Noun

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[fahy-loj-uh-nee]

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Phylogeny

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The evolutionary history and development of a species or a group of organisms, often depicted in a branching diagram.

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Example: This diagram shows a phylogenetic tree, which maps the evolutionary relationships between species. The branches show how different species (A-E) evolved from common ancestors over time.

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Cladistics Noun

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[kluh-dis-tiks]

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Cladistics

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A method of biological classification that groups organisms based on shared, unique characteristics that originate from a common ancestor.

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Example: This diagram, a cladogram, shows how scientists use shared characteristics to group organisms. For example, mammals and birds are grouped together because they are both endothermic.

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Cladogram Noun

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[klad-uh-gram]

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Cladogram

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A branching diagram that illustrates the evolutionary relationships among various species based on shared derived characteristics from a common ancestor.

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Example: A cladogram shows evolutionary relationships among species, helping to understand their classification.

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Clade Noun

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[kleyd]

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Clade

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A group of organisms, including a common ancestor and all of its descendants, representing a single branch on a cladogram.

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Example: This diagram shows an evolutionary tree. A clade is a group that includes one common ancestor and all of its descendants, like all the branches inside the 'Clade I' box.

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Derived characters Noun

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[dih-rahyvd kar-ik-ters]

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Derived characters

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Traits that appear in recent parts of a lineage but not in its older members, used to group organisms.

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Example: This diagram shows how new traits, or derived characters, appear in an evolutionary line. For example, the 'fuzzy tail' is a derived character shared by species B, C, D, and E.

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Dichotomous Key Noun

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[dahy-kot-uh-muhs kee]

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Dichotomous Key

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A tool used to identify organisms based on a series of choices between alternative characteristics.

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Example: This flowchart shows how a dichotomous key works by using a series of yes/no questions about plant features to identify different plant groups.