Animal Kingdom

Phylum Arthropoda

On a pleasant evening, you decide to go to a park. However, you end up having painful itchy eruptions on the skin. Clearly, you were bitten by an insect. After all, insects are everywhere. They belong to a group of animals called the Phylum Arthropoda, which form the largest percentage of the world’s organisms. They make up about 80 percent of the known species of animals! It is quite hard to escape them.

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Phylum Arthropoda

Arthropods are joint-legged animals and you must have come across a few of these animals. Some prominent ones include insects, spiders, ants, bees, crabs, shrimps, millipedes, centipedes etc. Scientifically speaking, they all come under the Animal Kingdom under phylum Arthropoda.

The success of the arthropods can mainly be attributed to the presence of exoskeleton, which makes them versatile, is protective in nature and also allows flexibility and mobility. You can see arthropods living on land and in water. They are also a source of food for many animals and human beings too!


(Source: Pinterest)

Learn more about Phylum Coelenterata here.

Characteristic features of Phylum Arthropoda

  • The body structure shows bilateral symmetry.
  • They are triploblastic.
  • They can be found in all types of habitats – land, water and soil.
  • They have jointed limbs.
  • The body is segmented into three regions – Head, Thorax and Abdomen.
  • The body cavity is filled with blood and is called the haemocoel. The blood is white in colour.
  • The exoskeleton is hardened and is made of chitin.
  • They have a well-developed central nervous system.
  • The head is well developed and bears the sensory organs and brain.
  • They have compound eyes and mosaic vision.
  • The digestive tract is complete with the mouth and anus at opposite ends of the body.
  • They have an open circulatory system with dorsal heart and arteries.
  • Respiration is through the general body surface or by gills in aquatic forms and through trachea or book lungs in terrestrial forms.
  • Sexes are separate and sexual dimorphism is exhibited.


(Source: Pinterest)

Learn more about Phylum Aschelminthes here.


  • Limulus polyphemus (King Crab)
  • Scorpions
  • Spiders
  • Ants
  • Prawns
  • Crabs
  • Cockroach
  • Butterfly
  • Mosquito

Learn more about Phylum Echinodermata here.

Solved Questions for You

Q: Write a few lines on the exoskeleton in Arthropods.

Ans: The exoskeleton in Arthropods is hardened and is made of chitin. It can be further stiffened in a few species by calcium carbonate. In arthropods, the exoskeleton is non-expandable and hence as the organism grows, it has to shed its exoskeleton so that it can be replaced by a new exoskeleton. This process is called moulting.

Q: Name a few arthropod insects that are carriers of diseases.






Housefly Typhoid, cholera, Diarrhoea
Sandfly Kala-azar
Mosquito Filariasis, Dengue Fever, Malaria
Rat Flea Bubonic plague
Tsetse fly African Sleeping sickness

Q: Book lung is a characteristic of which Phylum?

Ans: Phylum Arthropoda

Q: What is the process of conversion of small cockroach into an adult cockroach?

Ans: Metamorphosis

Q: The coelomic cavity in Phylum Arthropoda is filled with?

Ans: Haemocoel

Q: Which is the largest Phylum and state a few distinguishing features?

Ans: The largest phylum is Phylum Arthropoda. The distinguishing features are:

  • Presence of jointed legs
  • Body is divided into head, thorax and abdomen
  • Body is bilaterally symmetrical and triploblastic.
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