The animal kingdom

Select language :

The fundamental features such as level of organization, symmetry, cell organization, coelom, division, notochord, etc., have enabled us to classify the animal kingdom broadly.

In addition to the fundamental features, there are many other distinctive traits that are specific to each phyla or class.

Main features of the different phyla in the animal kingdom

Phylum Level of Organisation Symmetry Coelom Segmentation Respiratory System Digestive System Circulatory System Distinctive Features
Porifera Cellular Various Absent Absent Absent Absent Absent Body with pores and canals in walls.
Coelenterata (Cnidaria) Tissue Radial Absent Absent Absent Incomplete Absent Cnidoblasts present.
Ctenophora Tissue Radial Absent Absent Absent Incomplete Absent Comb plates for locomotion.
Platyhelminthes Organ &mps; Organ- system Bilateral Absent Absent Absent Incomplete Absent Flat body, suckers.
Aschelminthes Organ- system Bilateral Pseudo coelomate Absent Absent Complete Absent Often worm- shaped, elongated.
Annelida Organ- system Bilateral Coelomate Present Absent Complete Present Body segment- ation like rings.
Arthropoda Organ- system Bilateral Coelomate Present Present Complete Present Exoskeleton of cu- ticle, jointed ap- pendages.
Mollusca Organ- system Bilateral Coelomate Absent Present Complete Present External skeleton of shell usually present.
Echinodermata Organ- system Radial Coelomate Absent Present Complete Present Water vascular system, radial symmetry.
Hemichordata Organ- system Bilateral Coelomate Absent Present Complete Present Worm-like with proboscis, collar and trunk.
Chordata Organ- system Bilateral Coelomate Present Present Complete Present Notochord, dorsal hollow nerve cord, gill slits with limbs or fins.

Porifera include multicellular animals that exhibit a cellular level of organization and contain distinctive flagellated choanocytes. Coelenterates have tentacles and bear cnidoblasts.

They are mostly aquatic, sessile or free-floating.

Porifera include multicellular animals that exhibit a cellular level of organization and have characteristic flagellated koanocytes.

Coelenterates have tentacles and bear cnidoblasts. They are mostly aquatic, sessile or free-floating.

Ctenophores are marine animals with comb plates. The body of Platyhelminths is flat and exhibits bilateral symmetry.

Parasitic forms show distinct suckers and hooks.

Aschelminthes are pseudocoelomates and include parasitic as well as non-parasitic roundworms.

Annelids are metamerically segmented animals with a true coelom. Arthropods are the most abundant group of animals that are characterized by the presence of jointed appendages.

Mollusks have a soft body surrounded by an outer calcareous shell. The body is covered with an outer skeleton made of chitin.

Echinoderms have a spiny skin. Their most distinctive feature is the presence of a water vascular system.

Hemichordates are a small group of worm-like marine animals. They have a cylindrical body with proboscis, collar and trunk.

Phylum chordata includes animals that have a notochord either throughout or during early embryonic life.

Other common features seen in chordates are the dorsal, hollow nerve cord and paired pharyngeal gill slits.

Some vertebrates do not have jaws (Agnatha), while most have jaws (Gnathostomata).

Agnatha is represented by the class, Cyclostomata. They are the most primitive chordates and are ectoparasites on fish.

The Gnathostomata have two classes:

1. Pisces and

2. Tetrapoda.

Chondrichthyes and Osteichthyes have wings for class locomotion and are grouped under the sign Pisces.

Chondrichthyes are fish with cartilaginous endoskeleton and are marine.

The classes, Amphibia, Reptiles, Aves and Mammals, have two pairs of limbs and are thus grouped under Tetrapoda.

Amphibians have adapted to live both on land and in water. Reptiles are characterized by the presence of dry and scaly skin.

Limbs are absent in snakes. Fish, amphibians and reptiles are poikilotherms (coldblooded).

Aves are warm-blooded animals with feathers on their bodies and front legs modified into feathers for flight.

The hind limbs are adapted for walking, swimming, sitting or clapping.

Unique features of mammals are the presence of mammary glands and hair on the skin. They usually display vivacity.