Chapter 10-Mollusks Flashcards
What does Phylum Mollusca consist of?
clams, mussels, scallops, oysters, snails, slugs, nudibranchs (sea slugs), cuttlefish, squids, and octopuses
What is a mollusk?
soft-bodied creature with some sort of shell
Where do most mollusks live?
marine environments; many freshwater and terrestrial environments
What are the 3 parts of a basic mollusk body plan?
mantle, foot, visceral mass
What is the mantle cavity?
space through which water, or in some cases air, circulates
What is the reason for the circulation?
fresh oxygen for gas exchange
What is Ctenidia?
vascularized filamentous projections derived for the mantle, housed within the mantle cavity and function as gills in aquatic species
T/F Nitrogenous waste from excretory system and solid wastes from the digestive system empty into the mantle cavity and are swept away in a current flow.
True
What does the mantle produce?
shell
What is the foot and what does it do?
muscular structure used for locomotion by most mollusks, some specifically for prey capture
What does the visceral mass contain?
most of the internal organs such as the digestive, excretory, and reproductive systems
What is the coelom like in mollusks?
small spaces around excretory organs, heart, and intestines
What does the shell contain?
2 layer sof calcium carbonate covered by an organic layer of the protein conchin
What is the outer layer of shell?
periostracum which protects the inner calcium-rich layers from erosion
What is the inner layer of shell?
nacreous layer which is secreted continuously by the mantle
What is the layer between the periostracum and nacreous layer?
prismatic layer made form densely packed crystals of calcium carbonate
What is the shell used as?
spacious retreat for the soft and vulnerable body; in some groups the shell has been reduced, internalized, or lost (slugs, cephalopods, cuttlefish, squid and octopus)
What are member of the Class Polyplacophora called?
chitons
What are characteristics of Class Polyplacophora?
grazing herbivores found in shallow marine environments, have dorsoventrally flattened ovoid bodies covered with 8 overlapping calcareous plates; head is poorly developed and hidden beneath a girdle formed by a thick mantle; most of ventral surface occupied by a large, muscular, elongate foot which animal uses to move slowly across a hard substrates
What do chitons use the foot for?
suction, adhere tightly to surfaces
What do chitons lack?
antennae and eyes
What is a radula?
hard, grooved surface that animals use to scrape and grind algae off rock and other surfaces
What is the mantle cavity’s purpose in chitons?
contains ctenidia (gills), surrounds foot on all sides
What animals are in Class Bivalvia?
clams, mussels, scallops, and oysters
Where do bivalves live?
most are marine and some live in freshwater
How are bivalves usually recognized?
2 lateral shells hinged together and causes them to gape open
What draws the 2 shells together?
one or two large adductor muscles
What does the mantle secrete?
shells and ligament and envelops the internal organs within the shells
How do pearls form?
irritant like a grain of sand, lodges between the mantle and the shell, the mantle responds by surrounding the irritant with layers of the same crystalline material used for the shell
What is the foot used for in Class Bivalvia?
anchoring animal to substrate, creeping, or burrowing in soft sediments
Do bivalves have a radula?
no
Do bivalves have a distinct head region?
no
How do members of Class Bivalvia capture food?
gills; water circulates through mantle cavity and small food particles trapped in mucus covering gill surface; near mouth, food particles are gathered by flaps of tissue called labial palps which roll to direct food in the mouth; movement of cilia on surface of gills also creates current flow through the mantle cavity; water enters and leaves the mantle cavity through openings called siphons
What do siphons do in the bivalves that burrow?
extend to surface of the substrate to facilitate water circulation through the body
What animals belong to Class Gastropoda?
limpets, snails, slugs, and nudibranchs (sea slugs)
Do gastropods have shells?
most do which is often coiled, slugs and nudibranchs have lost their shell
How do gastropods move?
crawl on muscular foot, but foot has been modified in some for swimming such as nudibranchs
Do gastropods have a radula?
yes, used for scraping food off of hard surfaces
T/F Gastropods are herbivores but some are scavengers or predators.
True
Gastropods go though torsion. What is torsion?
asymmetric growth that repositions the mantle cavity and anus form the posterior part of the body a location nearer to the head
What species belong to Class Cepahlopoda?
squid, octopus, cuttlefish, and nautilus
T/F Cephalopods are herbivores.
False: carnivorous
How are cephalopods specialized?
well developed sensory, nervous, locomotion systems; largest brains and well-developed eyes among invertebrates
What are features of the cephalopod body?
consists of a foot, head, and visceral mass as we’ll as a mantle, mantle cavity, radula, paired gills, and reduced shell
Where are the fills housed in cephalopods?
mantle cavity
What makes a foot in a cephalopod so unique?
developed into a ring of arms and tentacles which are usually covered in suction cups
What are the arms used for?
appendages for capturing prey but in octopus arms they are also used for locomotion
How does water flow in cephalopods?
muscular action of the mantle wall-drawn in mantle cavity by mantle expansion, when mantle contracts, it forms a tight seal around visceral mass and then forces the water out a narrow tubular funnel (siphon) exiting mantle cavity
What is the pen or cuttlebone for?
counter the tendency of the body to lengthen during muscle contractions
