Coelom Vs Pseudocoelom: Definition, Types, Differences, Functions and Examples

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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

Phylum Platyhelminthes : General Characteristics and Its Classification

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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

Phylum Arthropoda: General Characteristics and Its Classification

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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

Phylum Echinodermata: General Characteristics and Its Classification

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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

Phylum Mollusca: General Characteristics and Its Classification

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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

Phylum Cnidaria/Coelenterata: General Characteristics and Its Classification

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Leuckart (1847) first coined the name Cnidaria. The term ‘Cnidaria’ is derived from two words; Gr. Knide=nettle and L. aria=like or connected with. Cnideraia are also known as Coelenterata. They have diverse colorful, radially symmetrical bodies which are known as the flower of the sea. The phylum Cnidaria contains more than 10,000 living species, among … Read more

Phylum Annelida: General Characteristics and Its Classification

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The representatives of the phylum Annelida are known as segmented worms or ringed worms. Annelida is derived from Latin word ‘anellus’ meaning little ring. It is a large phylum with over 22,000 living species. Among them,  Polychaetes constitute about 12,000 species while Clitellates contains about 10,000 species. The major groups include earthworms, ragworms and leeches. … Read more

Porifera : Characteristics and Classification

Scottish Anatomist and Zoologist Robert Edmond Grant proposed the name Porifera (L. Porus, pore and ferre, to bear). The representatives of Phylum Porifera are also known as Sponges. They are simple types of aquatic invertebrates. This phylum contains about 10000 species; among them, most of the species are Marine and some are freshwater (about 100 species). … Read more

Animal Classification: Basis, Principles, Importance of Classification and Rules of Binomial Nomenclature

There are approximately 8.7 million species on earth and their variety is simply astonishing. Besides, no two individuals of any animal-form are exactly alike. Hence, there must be some arrangement to group them in orderly categories to study the animal world. The diversity or differences also signify that organisms are really not so different from … Read more