CBSE Class 10 Answered

Fragmentation is only seen in multicellular organisms with a simple body organisation, On the other hand regeneration is observed in fully differentiated multicellular organisms. Another important point to remember is that regeneration takes place with the help of certain specialized cells. 

Renegeration is the growing back of a lost part of the body of an organism. It is also used as a method of defence. Fragmentation is the unintentional cutting up of the body of an organism which each grows into a different organism.