GENERAL CHARACTERISTICS OF ARTHROPODA

Gr.,arthros=joint; podos=foot

They are mostly terrestrial, but some are aquatic.
They may be herbivores, carnivores, omnivores or may be parasitic in nature.
Triploblastic animals i.e., body derived from 3 germ layer (ectoderm, mesoderm and endoderm).
Body is bilaterally symmetrical.
Body is metamerically segmented.
True coelom is reduced to form a blood filled cavity called haemocoel. So, these animals are termed as Haemocoelomate.

Jointed appendages are found, which have diversified functions. Walking legs are present those helps in locomotion.
Respiration is direct (through normal body surface) or through gills or tracheae or may be the book lungs.
Digestive system is complete type.
Excretion takes place through Malpighian tubules or green glands.
Blood vascular system is open type. A dorsal heart is present.
Nervous system includes a dorsal brain, a ventral primitively paired longitudinal nerve cord with ganglia from which lateral nerves extends from each segment.
Sense organ may includes simple eyes (oceli and stemmata), compound eyes, tactile or chemo-receptors, balancing and auditory organs.
Sexual reproduction takes place. Development is mostly indirect i.e., through various larval stages.
Mostly fertilization is internal, but most of the aquatic species have external fertilization.
Dioecious animals.