Practice question

Chelicerate body divided into two primary tagmata rather than three in insects. Anterior prosoma or cephalothorax results from fusion of six segments, dorsal carapace covering eyes, chelicerae, pedipalps and four pairs of walking legs, concentrated sensory and locomotory function. Posterior opisthosoma or abdomen contains twelve segments often reduced, bearing genital aperture, respiratory organs like book lungs or book gills, spinnerets in spiders and telson in scorpions. Narrow pedicel in spiders separates prosoma and opisthosoma allowing flexibility. This bipartite prosoma-opisthosoma organization contrasts with head-thorax-abdomen pattern defining chelicerate tagmosis.