Phylum Arthropoda - General Characters

Phylum Arthropoda is the largest among Invertebrates, in terms of number of species and considered biologically most successful animal group. The characters that contributed to their success are presence of a hard chitinous exoskeleton, body segmentation, jointed appendages, more developed nervous system and sense organs etc.They include about 75 to 80% of known animals on Earth containing about 1 million genera and many millions to be identified.
Arthropods got their name from two greek words - 'Arthros' means jointed and 'podos' means foot. So arthropods can be defined as 'Invertebrates with jointed legs'. It is the only phylum to have animals that are capable of flying.
They are present in all types of habitats viz., aquatic (both freshwater and marine water), terrestrial, aerial, fossorial, arboreal etc. They are adapted to new habitats very fastly.
They have originated from annelidan ancestors. According to one view, both annelids and arthropods were evolved from same group of ancestors. Inspite of different views, annelidan ancestry is evident in certain characters which are as under:
1. Segmented body
2.Plan of nervous system
3. Determinate type of cleavage.