a. Insecta: extremely diverse in habitat, have head, thorax and abdomen, generally sexually reproduction w/ different sexes, but many are asexual with parthenogenesis, most undergo complete metamorphosis
b. Crustacea: have 2 sets of antennae, live mostly in marine +freshwater environments, 2 tagmata cephalothorax and abdomen, have a carapace, many pairs of specialized appendages, sexual reproduction with internal fertilization but eggs released when hatched, many species include a larval stage called a nauplius.
c. Chelicera: Arachnida, 2 tagmata (cephalothorax and abdomen), appendages include 4 pairs of legs, 1 pair of chelicerae (for feeding, defense, copulation, movement, or sensory), 1 pair of pedipalps (used in sexual reproduction), some are predators, some are parasites, some are detritus, digestion begins externally in spiders, reproduction is sexual with internal fertilization, extensive courtship displays, metamorphosis does not occur, no larval forms
i. Include sea spiders, horseshoe crabs, daddy longlegs, scorpions, mites, ticks, spiders