Phylum Arthropoda -Biology

Phylum Arthropoda

Fig: Apis (Honey Bee)

Important Characteristics:

• It is the largest phylum of Animalia.

• Exhibit organ-system level of organization.

• Bilaterally symmetrical, triploblastic, segmented & coelomate animals.

• Metamorphic segmentation as in annelids but segmented not separated from each other by septa.

• All arthropods have an exoskeleton of a chitinous cuticle. 

• Cuticle shed periodically to allow for growth.

• The process of casting off of skin or integument is known as ecdysis or molting.

• The body is divisible into the head, thorax & abdomen or divisible into cephalothorax and abdomen.

• They have jointed appendages (arthos-joint, poda- appendages).

• Arthropods have an open circulatory system. The body cavity is known as hemocoel (hemocoel), is filled with fluid hemolymph.

• Respiration takes place through the general body surface & gills in crustacean; through trachea in insects, Diplopoda, Chilopoda; through book lungs in Arachnida.

• Excretion is brought about by green glands in aquatic forms & Malpighian tubules in terrestrial forms.

• Sexes usually separate; Fertilization internal; oviparous or ovoviviparous; development direct or indirect.

• Example: Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect).