Mollusca
The Phylum Mollusca
Etymology:- From the Latin Molluscus meaning soft of body. | Characteristics of Mollusca:-
1)Bilaterally symmetrical.
2)Body has more than two cell layers, tissues and organs.
3)Body without cavity.
4)Body possesses a through gut with mouth and anus.
5)Body monomeric and highly variable in form, may possess a dorsal or lateral shells of protein and calcareous spicules.
6)Has a nervous system with a circum-oesophagal ring, ganglia and paired nerve chords.
7)Has an open circulatory system with a heart and an aorta.
8)Has gaseous exchange organs called ctenidial gills.
9)Has a pair of kidneys.
10)Reproduction normally sexual and gonochoristic.
11)Feed a wide range of material.
12)Live in most environments | The mollusks constitute one of the largest phyla of animals, both in numbers of living species (at least 47,000, and perhaps many more) and in numbers of individuals. A significant characteristic of mollusks is their possession of a coelom, a fluid-filled cavity that develops within the mesoderm. The coelom not only functions as a hydrostatic skeleton but also provides space within which the internal organs can be suspended by the mesenteries. All mollusks have a soft body (their name is derived from the Latin word mollus, meaning "soft"), which is generally protected by a hard, calcium- containing shell. In some forms however, the shell has been lost in the course of evolution, as in slugs and octopuses, or greatly reduced in size and internalized, as in squids. Structurally, mollusks are quite distinct from all other animals. However, all modern mollusks have the same fundamental body plan. There are three distinct body zones: a head-foot, which contains both the sensory and motor organs; a visceral mass, which contains the well-developed organs of digestion, excretion, and reproduction; and a mantle, a specialized tissue formed from folds of the
Etymology:- From the Latin Molluscus meaning soft of body. | Characteristics of Mollusca:-
1)Bilaterally symmetrical.
2)Body has more than two cell layers, tissues and organs.
3)Body without cavity.
4)Body possesses a through gut with mouth and anus.
5)Body monomeric and highly variable in form, may possess a dorsal or lateral shells of protein and calcareous spicules.
6)Has a nervous system with a circum-oesophagal ring, ganglia and paired nerve chords.
7)Has an open circulatory system with a heart and an aorta.
8)Has gaseous exchange organs called ctenidial gills.
9)Has a pair of kidneys.
10)Reproduction normally sexual and gonochoristic.
11)Feed a wide range of material.
12)Live in most environments | The mollusks constitute one of the largest phyla of animals, both in numbers of living species (at least 47,000, and perhaps many more) and in numbers of individuals. A significant characteristic of mollusks is their possession of a coelom, a fluid-filled cavity that develops within the mesoderm. The coelom not only functions as a hydrostatic skeleton but also provides space within which the internal organs can be suspended by the mesenteries. All mollusks have a soft body (their name is derived from the Latin word mollus, meaning "soft"), which is generally protected by a hard, calcium- containing shell. In some forms however, the shell has been lost in the course of evolution, as in slugs and octopuses, or greatly reduced in size and internalized, as in squids. Structurally, mollusks are quite distinct from all other animals. However, all modern mollusks have the same fundamental body plan. There are three distinct body zones: a head-foot, which contains both the sensory and motor organs; a visceral mass, which contains the well-developed organs of digestion, excretion, and reproduction; and a mantle, a specialized tissue formed from folds of the