Mollusk Anaylsis

All week in marine biography, we have been learning about mollusks.  On Wednesday, we dissected a clam. and on Thursday we dissected a squid.  The mollusks have a morphological feature after which the phylum is named.  The word "mollusk" means "soft thing."  Therefore, mollusks have soft bodies which explains the name of the phylum.  Since mollusks have soft bodies, they face biological troubles.  Because of their soft body, they are more fragile.  Along with that, they have more difficulty to support their bodies in terrestrial environments or to fixate to substrates in aquatic habitats.  A lot of mollusk species solve this problem by having a shell to support and protect them, and also to prevent dehydration.  Mollusks are divided into classes.  The five classes are: pelecypods, or bivalves, which includes oysters, clams and mussels.  Gastropods include snails and sea slugs.  Cephalopods include squids and octopuses.  Scaphopods include tooth shells.  And polyplacophora include chitons.  All the animals we dissected in class had a vertical symmetry.  Each animal we dissected down the middle and they all were pretty much the same in their own being.  The clam had a hard but smooth shell that was very hard to open, the inside of it was very gooey and slimy.  The squid was overall squishy and soft and were clearly no bones in it, but there are two parts of it that are hard which was the beak and the pen.  The pen supports the squid and gives it structure but isn't a bone, and the beak is it's mouth, and those are the only two hard spots.