Phylum Arthropoda was established by von siebold.the term arthropod means jointed-legged animal.In numbers of species and individuals the arthropods surpass the members of other phyla.Arthropoda constitute about 80% of the known animal species.
Arthropods include spiders,scorpions,crabs,prawns,centipedes,millipedes,insects etc.insecta constitutes the largest class in the animal kingdom.Arthropods have adapted themselves to diverse habitats,like water,land and air.Arthropods are the most successful of all the known animal groups.They exhibit the greatest adaptive radiation.
The success of arthropods is chiefly due to the following:
1)A comparatively hard and rigid exoskeleton,which is in the form of chitinous cuticle helps in the maintenance of the shape of the body.Waxy epicuticle prevents dehydration in terrestrial arthropods.
2)Jointed legs/appendages show rapid movement with the help of bundles of striated muscles.Striated muscles appeared for the first time in the arthropods among the invertebrates.
3)An extensive haemocoel(blood-filled body cavity) is a part of open type of blood vascular system.This open type of blood vascular system serves to bathe the tissues of all organs with blood(haemolymph).
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