The liquid filled cavity between alimentary canal and body wall of multicellular triploblastic animals is known as body cavity. Generally, the body cavity that is lined by mesodermal peritoneal membrane is known as coelom. According to Hyman (1955), coelom is the hollow space between alimentary canal and body wall which is lined by mesodermal peritoneal … Read more
The term ‘Echinodermata’ is derived from Greek words ‘echinos’ meaning ‘spiny’ and ‘dermos’ meaning ‘skin’. The representatives of phylum Echinodermata are absolutely marine organisms and this phylum contains about 7,000 known living species. Among them, notable species are sea urchins, brittle stars, sand dollars, sea cucumbers, sea stars, etc. Scientists did not trace any freshwater … Read more
The chordates were originated from a fish-like ancestor, very similar to the larva of the Ascidia (Tunicata) and it is assumed that they became the ancestor of the chordates by retaining the larval form throughout the life. In the palaeozoic age, the chordates were originated from some sessile Echinoderms, which were bottom dwellers of the … Read more
Phylum Arthropoda is the largest animal group which constitutes the largest percentage of the world’s organisms. It is estimated that about 84% of all known species of animals belong to this phylum and number of known species vary between 1,170,000 and 5 to 10 million. Besides these, many arthropods are not yet unidentified. Some prominent … Read more
Mollusca makes the second largest phylum of non-chordate animals including snails, octopuses, sea slugs, squid, and bivalves such as clams, oysters, and mussels. This phylum contains about 100,000 described species. Among all known marine species, 23% are mollusks. But some species live in freshwater and terrestrial habitats. This group displays a broad range of morphological … Read more
The representatives of the phylum Platyhelminthes are commonly known as the flatworms or tapeworms. The word ‘Platyhelminthes’ is derived from the Greek word, ‘platy’ meaning flat and ‘helminth’ meaning worm. They are simple soft-bodied, bilaterian, unsegmented invertebrate animals. The Phylum Platyhelminthes makes up the 4th largest phylum among the animal kingdom. But among the acoelomate … Read more