12. Phylum Mollusca Notes
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Transcript of 12. Phylum Mollusca Notes
MollusksKingdom Animalia
Phylum MolluscaClass GastropodaClass BivalviaClass Cephlapoda
Mollusks50,000 species10 classesIncludes:
◦ Squid◦ Octopus◦ Clams◦ Conches◦ Snails◦ Sea slugs◦ Oysters
Basic Anatomical Structures:a) Mantle – muscular bag that
surrounds the gills and most organs and is used to circulate water
1. some use it to circulate water or jet propulsion
2. secretes calcium carbonate shell
Basic Anatomical Structures:b) Foot – muscular structure used for
movement
1. In snails & slugs it’s used to crawl
2. In bivalves it’s used to dig
3. In squids, it takes the form of tentacles
Basic Anatomical Structures:
c) Radula – a tongue like structure with scraping teeth
Class Gastropoda
Includes snails, slugs, whelks, & abalone
Defining Characteristics:
- Radula- Some have a shell- Sensitive Tentacles- Shell-less members
can produce toxins or store eaten nematocysts
Snails Sea Slugs
Whelks Abalone
Class Bivalvia:
Includes clams, oysters, mussels, scallops
Defining characteristics:
- Two hinged shells- No head, but
sensory organs on shells edge
- Two siphons extend out of the shell
- Mantle pumps water
Clam Oyster
Mussel Scallop
Clam Oyster
Mussel Scallop
Pearl Making Abilities
When ever sand or an irritant gets inside a shell of an oyster, it coats it in a substance called nacre, creating a pearl
Pearl farmers put seeds inside oysters to create pearls
Class Cephalopoda
Includes squid, octopus, nautilus, cuttlefish
Defining Characteristics:
- Little to no shell, ranging from gastropod like shell (nautilus) to internal leaf like shell (cuttlefish) to thin internal bar called a pen (squid) to nothing (octopus)
Class Cephalopoda
Defining Characteristics:- Specialized foot called a siphon for jet
propulsion- Ink sac- Chromatophores – cells that can change
color- Complex nervous systems consisting of
large eyes and critical thinking abilities
Octopus8 armsBeak like jawsNo shellBottom dwellers
SquidBetter adapted for
swimming due to elongated body and two fins formed by the mantle
Ten arms, two of which are longer are called tentacles
A reduced shell called the pen can be found embedded in the upper surface
CuttlefishResemble squidsEight arms and
two tentaclesFlattened with a
fin along the sides
Internal Shell
NautilusSmooth exterior
shellContains several
gas filled chambers that aid in buoyancy
Has 60-90 arms to catch prey