The Living Organisms hierarchy consists of terms for plants and animals intended for cataloging art, architecture, and related disciplines. It is not comprehensive: it grows as needed by contributions. Records include common names as well as scientific names for plants and animals, where appropriate (e.g., "Canis lupus" and "gray wolves"). Note that this hierarchy does not duplicate scientific taxonomies: it includes levels and records that are inappropriate for a scientific taxonomy but are necessary for the target audience of the AAT. The hierarchy combines living and extinct animals and plants, animals or plants by location and context (e.g., "waterfowl"), common names that have no direct counterpart in a scientific taxonomy because they do not correspond to a single species or genus (e.g., a generic "zebra"), groups of animals (e.g., "flocks"), components of animals (e.g., "paws"), and other divisions that are not part of a scientific taxonomy. Levels found in a scientific taxonomic tree occasionally may be omitted here. Records for animals or plants may be linked through Associative Relationships to records for the products derived from them, particularly when the product is unique and used to produce architecture or art (e.g., "calfs (animals)" [are] source of "vellum (parchment)"). The preferred scientific names and the basic underlying structure of the AAT hierarchies are usually derived from encyclopedia and other authoritative general reference sources rather than the most recent scientific taxonomies: taxonomic classifications have been in flux since the 1980s and many competing classifications exist, some based on traditional morphological evidence and others on analyses of molecular data. It is out of scope for the AAT to reflect the most current developments in this field.