LABORATORY 7 PHYLUM MOLLUSCA Shared by: ChrisCaflish LABORATORY
7: PHYLUM MOLLUSCA The phylum mollusca is one of the largest of
all phyla, both in the size of certain species and the number of
species which have been described. There are approximately
90,000 described species. Early molluscs were abundant in
cambrian seas and the long history of the group is reflected
today in the variation among molluscan types. This variation
also attests to the success and plasticity of the basic
molluscan body plan, which is far from obvious in some modern
members of the phylum. The basic molluscan body plan is
bilaterally symmetrical, unsegmented, protostomate, and
coelomate and the body is divided into a ventral muscular foot,
a dorsal visceral mass, and a mantle (pallium) of epithelium and
other tissue which encloses the dorsal surface of the body. The
cavity between the mantle and visceral mass is termed the mantle
cavity. The visceral mass is provided with a blood circulatory
system generally containing the oxygen ca