Practice question

Tardigrada constitute microscopic eutelic ecdysozoan metazoans inhabiting water films on mosses, lichens, soil and aquatic biofilms, famously termed water bears or moss piglets because stocky barrel body with four pairs stubby lobopod legs ending in claws, lumbering bear-like gait and teddy bear face appearance microscopically. Bilaterally symmetrical with four trunk segments, cuticle moulted regularly, cryptobiotic capacity renowned. Phylogenetically sister to arthropods and onychophorans within Panarthropoda. Despite minute 0.1-1.2 mm size, exhibit extreme tolerance to desiccation, radiation, vacuum. Common name reflects early microscopy descriptions by Spallanzani and popular interest in extremotolerant animals.