Notes on Arthropoda | Grade 11 > Biology > Introduction to kingdom Animalia | KULLABS.COM

Arthropoda

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  • Things to remember

Arthron→ Jointed

Podos → Legs

Von Siebold coined the term Arthropoda.

It is the largest group in an animal kingdom.

General characteristics of phylum Arthropoda:

  • This is the largest phylum. The animal of this group is found in all habitats.
  • They are triploblastic and bilaterally symmetrical.
  • Body consist of jointed appendages or legs.
  • The body is covered externally by a hard chitinous exoskeleton.It moulds periodically and replaces it by a new exoskeleton. It is called moulting.
  • The body is divisible into head, thorax, and abdomen. In some head and thorax is often fused to form cephalothorax as in prawn.
  • Cephalisation( A true head is present). It bears a pair of compound eyes, antenna and feeding apparatus.
  • It is a haemo-coelom type.
  • Locomotion takes place by paired lateral jointed appendages.
  • The alimentary canal is straight and well developed. The mouth bears mouth parts for ingestion of food. Mouths part are modified for biting, chewing, sponging, piercing, siphoning.
  • Respiration takes place by trachea or book lungs or gills.
  • The circulatory system is open type consisting of perivisceral and pericardial sinuses. Blood vessels are present.
  • Excretory organs take place by malpighan tubules, green glands or coxal glands. Voluntary muscles are present.
  • The nervous system consists of a brain and double solid nerve cord like Annelida.
  • Sense organs include antennae, compound eye, statocysts etc. The compound eye consists of many ommatidia to form several images.
  • They are unisexual i.e. male and female sexes are separate. Fertilization is internal. They are either oviparous or ovoviviparous.
  • Development is direct or indirect. In some species, parthenogenesis is seen.

Classification:

It is classified into four classes on the basis of the number of a locomotory organ. Around 9 lakh species are present.

Examples of class Crustacea and Myriapoda
source:tidechaser.blogspot.com
fig:Examples of class Crustacea and Myriapoda

Crustacea:

  • Five pairs of walking legs.
  • The body is divided into cephalothorax and abdomen.
  • The body is externally covered by a chitinous cuticle.
  • Head with two pairs of antennae.
  • Respiration by gills.
  • Example: Prawn, Crab, cyclops etc.

Myriapoda:

  • Many pairs of walking legs.
  • The body is divided into head and many segmented trunks.
  • Head with one pair of antenna.
  • Respiration by trachea.
  • Example: Julus, Scolopendra.

Insecta or Hexapoda:

  • Three pairs of walking legs.
  • The body is divided into head, thorax, and abdomen.
  • Head with one pair of antenna, compound eye and mouth parts.
  • Respiration by trachea.
  • Example: Periplaneta, Pieris.
Example of class Insects
source:www.britannica.com
fig:Example of class Insects

Arachnida:

  • Four pairs of walking legs.
  • The body is divided into persoma, mesosoma, and metasoma.
  • The head is without an antenna. It bears chelicerae and pedipalpi for capturing and tearing the prey.
  • Respiration by book lung and trachea.
  • Example: spider, scorpion.
Example of class Archndia
source:www.visualdictionaryonline.com
fig:Example of class Arachnida



  • It is the largest group in animal kingdom.
  • This is the largest phylum. The animal of this group are found in all habitats.
  • They are triploblastic and bilaterally symmetrical.
  • Body is covered externally by hard chitinous exoskeleton.
  • Locomotion takes place by paired lateral jointed appendages.
  •  Around 9 lakh speciesare present.
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