Shrimps, barnacles, scorpions, spiders, etc., all belong to which phylum?
Arthropod specialization of segments is in the head. The four major groups of arthropods – Chelicerata (includes spiders and scorpions), Crustacea (shrimps, lobsters, crabs, etc.), Tracheata (arthropods that breathe via channels into their bodies; includes insects and myriapods), and the extinct trilobites – have heads formed of various combinations of segments, with appendages that are missing or specialized in different ways. In addition, some extinct arthropods, such as "Marrella", belong to none of these groups, as their heads are formed by their own particular combinations of segments and specialized appendages. Working out the evolutionary stages by which all these different combinations
Predation some species such as the alderfly, only the larvae are predatory (the adults do not eat). Spiders are predatory, as well as other terrestrial invertebrates such as scorpions; centipedes; some mites, snails and slugs; nematodes; and planarian worms. In marine environments, most cnidarians (e.g., jellyfish, hydroids), ctenophora (comb jellies), echinoderms (e.g., sea stars, sea urchins, sand dollars, and sea cucumbers) and flatworms are predatory. Among crustaceans, lobsters, crabs, shrimps and barnacles are predators, and in turn crustaceans are preyed on by nearly all cephalopods (including octopuses, squid and cuttlefish). Seed predation is restricted to mammals, birds, and insects and is