Millions of animal species diverse in their size and shape have been reported on the earth. Inspite of differences in structure and form of different animals, there are fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems.
Besides the fundamental features, there are many other distinctive characters which are specific for each phyla or class.
The phylum poriferacomprises of sessile pore-bearing animals. They show a cellular grade of organisation. The members of phylum porifera are mostly marine, but few are fresh water. They are commonly called sponges. They are asymmetrical, diploblastic and acoelomate. They reproduce asexually by the process of fragmentation.
The members of phylum cnidariaare aquatic, mostly marine, sessile or free-swimming and radially symmetrical. They have a central gastro-vascular cavity. Cnidarians exhibit two basic body forms called polyp and medusa.
The members of phylum ctenophora are commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization. The body of ctenophores bears eight external rows of ciliated comb plates, which help them in locomotion.
The members of phylumplatyhelmintheshave dorso-ventrally flattened body, hence they are called flatworms. They arehermaphrodites, bilaterally symmetrical, triploblastic, acoelomate, invertebrate animals. The parasitic forms have suckers and hooks.
The members of phylum Aschelminthesare called roundworms as their body is circular in cross-section. They are aquatic, freeliving,terrestrial, parasitic in plants and animals.They are pseudocoelomate,bilaterally symmetrical, triploblastic and mostly unsegmented and are covered with cuticle.
The phylum annelid consists of multi-segmented, bilaterally symmetrical, triploblastic, coelomate, invertebrate worm-like animals. They may be aquatic, terrestrial, freeliving and sometimes parasitic. They exhibit organ-level of body organisation. Their body consists of numerous segments or metameres.
The phylum arthropodais the largest phylum of the kingdom animalia. They are found in freshwater, marine and terrestrial habitats.Their body is bilaterally symmetrical, triploblastic and coelomate. The body is divided into head, thorax and abdomen. They have jointed appendages.
The phylum mollusca is the second largest phylum of kingdom animalia. They are found in both terrestrial and aquatic habitats. They are bilaterally symmetrical, triploblastic, protostome coelomates. They have distinct head, muscular foot and a visceral hump present. The visceral hump is covered by mantle.
The members of phylum echinodermata areexclusively marine animals with peculiar body architecture. They are triploblastic and coelomate. The adults show radial symmetry while the larvae show bilateral symmetry. They possess a spiny skin.
Hemichordata is a group of marine animals categorised as either a phylum of deuterostomes or a subphylum of chordates.
The phylum chordate includes animals which possess notochord either during embryonic life or throughout the life.Phylum chordate is divided into three subphyla; Urochordata, Cephalochordata and vertebrata. The subphylum vertebrata is divided into Agnatha and Gnathostomata.
Gnathostomata consists of has two super classes, Pisces and Tetrapoda.
Tetrapoda includes classes, Amphibia, Reptilia, Aves and Mammalia.