The phylum mollusca is the second most diverse animal phylum with over 50,000 living species and mostly.

The mantle produces the shell. The advantage of a shell is to protect the creature and offer a portable home. It also has the disadvantage of taking more energy to move around. Whereas many mollusca have well-developed shells (snails, limpets etc.) while other have reduced shells (squid and some sea slugs) or no shell at all (octopuses).

The advantage of having a reduced shell, or no shell at all, can be the animal's speed and its ability to get into small cracks and holes because of its size.

Most mollusca have an open circulatory system expect for the class of cephalapode. This system is complete with a heart, blood vessels, and respiratory pigments. Gas exchange is via gills, lungs, or the body surface. Excretion takes place by means of kidneys that, like the digestive tract, pump waste into the mantle cavity. The disadvantage of an open circulatory system is in directing where the blood goes but an advantage is the organs are always covered by blood where blood empties into sinuses.

Most mollusca's have a radula. This is a toothed tongue-like organ used for feeding and defense.

The Phylum Mollusca has seven classes:

  • Class Polyplacophora - Chitons
  • Class Gastropoda - Snails, Slugs Limpets, Cowries
  • Class Bivalvia - Clams, Oysters, Scallops, Mussels
  • Class Cephalopoda - Octopuses, Squids, Nautiloids
  • Class Scaphopoda - Tusk shells
  • Class Aplacophora - Lack shells and worm like in shape
  • Class Monoplacophera - Limpet like appearance

Zonation | Intertidal Pools | Collection Etiquette

Kelp & Algae | Fungi | Porifera | Cnidaria

Mollusca | Echinodermata | Osteichthyes

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