In some animal groups, the body is found divided into compartments with at least some organs. This characteristic feature is called
1.
Segmentation
2.
Metamerism
3.
Metagenesis
4.
Metamorphosis
(b) Metamerism is the division of animal body, externally and internally into segments with a serial repetition of at least some organsm, e.g., annelids (earthworm).
However, Segmentation refers to the division of animal's body into a series of repetitive segments. It is external in arthropods, and internal in vertebrates.
Metagenesis is the phenomenon in which one generation of certain animals and plants reproduces asexually, followed by a sexually reproducing generation, i.e., alternation of generation (e.g., Obelia).
Metamorphosis is the developmental process in an organism through which it changes from one life form to another (eg., Order-Lepidoptera-Butterfly egg-larvae-pupa-adullt),
