1) segmented animals.
2) Body is covered with a thick chitinous cuticle forming an exoskeleton.
3) Body segments usually bear paired lateral and jointed appendages
4) Muscle is not continuous but comprises separate striped muscles.
5) Body cavity is haemocoel. The true coelom is reduced to the spaces of the genital and excretory organs.
6) Digestive tract is complete. Mouth and anus lie at opposite ends of the body.
7) Circulatory system is open with dorsal heart and arteries but without capillaries.
8) Respiration occurs through general body surface, by gills in aquatic forms, tracheae or lungs in terrestrial forms.
9) True nephridia are absent. Excretion takes by coelomoducts or malpighian tubules or green or coxal glands.
10)Cilia are absent from all the parts of the body.
11)Sexes are generally separate and sexual dimorphism is often exhibited by several forms.
12)Fertilization is internal. Development is usually indirect through larval stages.
13)Parents take care of the young one in many arthropoda.
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