### animal:

Mollusc
* All molluscs have a complete digestive tract starting with the mouth and ending with anus.
* Many molluscs also live in freshwater and terrestrial habitats.
* Most molluscs are capable of making pearls when foreign substances enter their shell
  - dioecious
  - marine though some inhabit freshwater and some are terrestrial
  - slow-movers
* Most molluscs have a head that nor- mally includes eyes and other sensory organs
  - well- defined nervous system with a primitive brain
  - calcareous shells
  - digestive tracts
  - eyes, and all have sensors that detect chemicals, vibrations and touch
  - gills
  - one pair of gills, or only one gill
  - separate sexes with gonads located in the visceral mass
  - structures
  - true gills, or ctenidia
  - unique structures
* Some molluscs display an unusual cell behavior during cleavage.
* Some molluscs excrete acid
  - amino acid
* Some molluscs have a calcareous shell that functions as an exoskeleton
  - tongue-like structure with rough protrusions similar to small teeth
  - coeloms
  - complex, extremely sensitive eyes
  - cord
  - feet
  - kinds
  - muscular feet
  - nerve cord
  - tentacles
  - survive many years
* are a highly diverse group in size, in anatomical structure, in behavior, and in habitat
  - very diverse phylum of invertebrates
  - adapted to life on land and in fresh or sea water
  - an extremely diverse group of organisms
  - animals so they belong to the animal kingdom
  - extremely diverse in tropical and temperate regions, but can be found at all latitudes
  - fundamentally bilaterally symmetrical
  - important components of the benthic fauna
  - protostomes, they have spiral cleavage and require separate sexes for reproduction
  - represented in soil communities by slugs and snails
  - soft bodied animals but most are protected by a shell that is usually hard
  - soft-bodied animals, more familiarly known as clams, octopods, and snails
  - species that live in freshwater and saltwater and are extremely varied in form
  - the second most valuable group of marine food species after fishes
* e.g. snails.
* have a circulatory system and most have a two-chambered heart
  - that transports nutrients and oxygen
  - mantle that secretes the calcium carbonate that makes up the shell
* have a soft body that is protected in many species by a hard shell
  - unsegmented body which is usually covered by a shell
  - three-chambered heart
  - an open circulatory system - only part of the blood flow is contained in vessels
  - more varied forms than any other animal phylum
  - one or two pairs of sponge-like nephridia, which are similar to kidneys
  - the widest range of body forms out of all invertebrates
  - tissue
  - very different characteristics one of their specialties is something called a coelom
  - well-developed sensory structures
  - carapaces
  - cells
  - shellfishes
  - vacuoles
* is an invertebrate
* live in the sediments of the pond and on aquatic plants.
* possess shells.
* provide the third most economically valuable fishery in the United States.
* retain shells.
* share characteristics
  - unique characteristics
* thrive in sea
  - shallow sea
* use shells.
* usually consist of a head, a soft body mass and a muscular foot.