Knowra Tagmosis Tagmosis Tagmosis is the evolutionary grouping of serial body segments into distinct functional regions, such as a head, thorax, and abdomen. It is especially prominent in arthropods.
Metamerism : The division of an animal body into a series of repeated segments along its length. Tagmosis modifies a segmented body plan by grouping segments into specialized regions.
Insect body plan : The insect arrangement of a head, three-segmented thorax, and abdomen. This is a familiar three-region pattern, with locomotory legs concentrated on the thorax.
Arthropod : An invertebrate animal with a segmented body, jointed appendages, and a chitinous exoskeleton. Arthropods display some of the clearest and most varied examples of tagmosis.
Pseudometamerism : The superficial repetition of body structures without the true serial segmentation seen in metameric animals. Repeated appearance alone does not constitute tagmosis, which groups genuine body segments.
Hox gene : A developmental regulatory gene that helps specify the identities of body regions along an animal's main axis. Changes in Hox gene expression can alter the identities and boundaries of segments grouped into tagmata.
Spider anatomy : The body organization of spiders, with a prosoma and opisthosoma connected by a narrow pedicel. Spiders show two major tagmata rather than the insect head–thorax–abdomen arrangement.
Evolution of arthropods : The evolutionary history of the animal group that includes insects, crustaceans, arachnids, and myriapods. Comparisons across arthropod lineages reveal how segment groups and their functions changed over time.
Somitogenesis : The embryonic process that forms somites, paired blocks of mesoderm along the vertebrate body axis. Somitogenesis creates repeated embryonic units, whereas tagmosis concerns the evolutionary grouping of segments.
Segmental identity : The developmental characteristics that distinguish one body segment from another. Distinct segment identities allow adjacent segments to specialize as parts of a shared functional region.
Crustacean anatomy : The body organization of crustaceans, often including a head, thorax, and abdomen or a fused cephalothorax. Crustaceans illustrate how segment grouping and fusion vary within arthropods.
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