You are given Leech,Nereis, Scolopndra; Prawn and Scorpion. All have segmented body organisation. Will you classify them in one group? If not give the important characters based on which you will separate these into different groups.

No (l) Leech and Nereis have metameric segmentation (i.e., external segmentation of body corresponding to internal segmentation), closed circulatory system and unjointed appendages. They belong to phylum Annelida.
(ii) Scolopendra (centipede), Prawn and Scorpion also have segmented body but they have open circulatory system, jointed appendages and chitinous exoskeleton. They belong to phylum Arthropoda.