Write an account on common characters of Arthropoda.

Explanation

(i) This is the largest phylum of the Kingdom Animalia and includes the largest class called Insecta.
(ii) They are bilaterally symmetrical, segmented, triploblastic and schizocoelomate animals with organ system grade of body organisation.
(iii) They have jointed appendages which are used for locomotion feeding and are sensory in function.
(iv) Body is covered by chitinous exoskeleton for protection and to prevent water loss, It is shed off periodically by a process called moulting or ecdysis.
(v) The body consists of a head, thorax, and abdomen with a body cavity called haemocoel.
(vi) Respiratory organs are gills, book gills, book lungs or trachea.
(vii) Circulatory system is of open type.
(viii) Sensory organs like antennae, eyes (compound and simple), statocysts (organs of balance equilibrium) are present.
(ix) Excretion takes place through malpighian tubules, green glands, coxal glands, etc.
(x) They are mostly dioecious and oviparous, fertilization is usually internal.
(xi) Iife history includes many larval stages followed by metamorphosis. eg. Limulus.