When the body of an organism is made up of similar parts, it is called fragmentation or metamerism. Each segment is called a metamere or somite.
(i) Asegment: Those animals which have no segmentation in their body are called non-segmented animals. Chordata are unsegmented animals. For example, humans (Homo sapiens), starfish (Asterias ruben) etc.
(ii) Homonomous metamere: Animals whose body is made up of similar segments are called homosegmented animals. Annelida is a group of animals. For example, earthworm (Metaphire posthuma), cockroach (Hirudinaria medicinalis) etc.
(iii) Heteronomous metamere: Those animals whose body is made up of unequal or different types of segments are called heteronomous animals. Animals of the order Arthropoda are unclassified. For example – cockroach (Periplaneta americana), Prajaprati (Pieris brassicae and Palilio krishna) etc.