4. Kingdom Animalia - part 08 - Phylum : Arthropoda

 

4. Kingdom Animalia - part 08 - Phylum : Arthropoda


Phylum : Arthropoda (Arthros : Joint, Podos : leg) :

  • e.g. Cockroach, Butterfly, Scorpion, Millipede , Prawn.
  • This is largest phylum of kingdom animalia. 
  • These animals have jointed appendages, hence the name -Arthropoda.
  • These are omnipresent and solitary or colonial, most of them are free-living (Barnacles are sedentary). 
  • Few are parasitic and sanguivorous (female mosquito, bed bug). 
  • Their body is bilaterally symmetrical, triploblastic, eucoelomate, metamerically segmented with tube within tube body plan and organ-system level of organization. 
  • Body is covered by tough, non-living chitinous exoskeleton. Hence, they need periodic moulting (ecdysis). 
  • Body is divided into head, thorax and abdomen.
  • Digestive system is complete.
  • Circulatory system is of open type, blood flows through body cavity (haemocoel). 
  • Respiratory organs are gills, trachea, book lungs, book gills.
  • Excretion takes by green glands, Malpighian tubules or coxal glands. 
  • Nervous system is formed by nerve ring and double, ventral, ganglionated nerve cord. 
  • Sense organs are well developed in the form of antennae, simple or compound eyes, various receptors. 
  • Sexes are separate showing sexual dimorphism, fertilization is generally internal, development is direct or indirect by metamorphosis. 
  • In some arthropods like honey bees, bugs etc. offsprings are produced by parthenogenesis. 
  • Some insects exhibit polymorphism e.g. honey bee, ants, termites etc. 
  • Some arthropods are economically important such as Apis (honey bees) for their honey and wax.
  • Lac is produced by Laccifer lacca (Lac insect). 
  • Lobsters, prawns and crabs are edible, silk worms produce silk.
  • Some arthropods are harmful which acts as vector e.g. mosquito. 
  • Locusta (locust) is a gregarious pest. Limulus (King crab) is known as living fossil.


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