Mollusca Flashcards
What is the literal meaning of molluscs
(molluscs is a latin word)
Soft fungus or small nut.
What is the text book molluscs?
“Hypothetical Ancestral Mollusc”
How are molluscs differentiated?
Using a Common Basic Body Plan
What is the body plan of Molluscs?
(Think of a snail)
A viseral mass, Mantle, Mantle cavity, Shell, Radula, and Head-foot portion
What is the most active part of a mollusc? Why?
(Think of a snail)
The head-food region as it accounts for the feeding, locomotion and have cephalic sensory.
Digestive, Circulatory, Respiratory and reproductive organs are present in?
Viseral mass
A sheath of skin extended from the viseral mass and hangs on both sides of the body.
Mantle.
This structure exists between the Mantle and Viseral Mass.
The Mantle Cavity.
This structure houses gills and lungs that developed from the mantle.
Mantle Cavity.
A fluid filled structure that is continuously washed by the water outside the mollusc.
The Mantle
What kind of action does the mollusc head-foot portion depend on for its function?
Muscular action
What does the viseral mass depend on for its functions?
Cilitary tract
This structure is a rasping protrusible, tongu-like organ found near the mouth.
Radula
In what mollusc is Radula not present in?
(Lab and s)
Bivalve and Solengasters
Describe the Radula.
- Ribbon like memberane mounted on rows of tiny teeth that point backwards.
- Odontophoes move the radula in and out of the mouth.
- The ribbon-like memrane is partly rotated over the tips of the cartilage or odontophore.
Describe the function of foot in the typical mollusc and a bivalve.
- Molluscs leave a trail of slime and it glides along it with waves of ciliary movement or muscular contraction.
- In bivalves the foot is used for rooting into sad or mud
Which structure secrets the shell?
The mantle
What is the purpose of the shell?
To protect from predators and supports the soft body.
How does the shell get its calcium?
- Food
- environmental water
- Soil
At what period of the mollusc life cycle does the shell first appear?
The larval period.
(which grows continuously through life i.e., the shell).
Name the shell layers
- Organic outer layer
- Calcareous middle layer
- Smooth inner layer.
What type of germ layer is present in the molluscs.
Triploblastic
What structures are involved in Gaseous exchange?
(4 structures)
- ctenidia (primary gill)
- Secondary gill
- Lung
- Mantle (Body surface area)
True or False. coelom is in most molluscs are highly reduced and limited by area around. What areas limited the coelom?
- Gonads
- Heart
- Parts of the kidney
- Intestine
What is the name of the pigments found in the blood of mollusc
(Starts with R)
Respiratory pigments.
What type of circulatory system does molluscs have?
Open circulatory system.
What. isthe flow of the circulatory system of molluscs?
Flows throught the vessel and enters the open sinuses in other parts of the body.
How does the blood flow in the circulatory system?
Blood moves to and from the tissues within the blood vessels.
What is the disadvantage of an open circulatory system and why is it best fo rmolluscs
- It is not efficient in supply O2 to all the tissues in the body and so it is common in slow moving organisms.
What organmis have a closed circulatory system?
(Cep + airpods)
cephalopods: squid, octopus, cuttlefish.
The digestive tract is equiped with..
extensive ciliary tract
Where does the anus empties into
The mantle cavity.
Monoplacophora
Limpets
cephalopods
squid, octopus
Bivalvia
Clams and mussels
Scaphopoda
tusk shells
Polyplacophora
Chitons
what is the second larges Molluscan class?
Bivalvia
Give examples of bivalvia
Clams, scallops, mussels, oyesters.
Describe Bivalvia
(how the shell is dived, type of org, and habitat found, how they feed)
- Compressed organisms.
- Shell divided into 2 valves.
- Shell divided into 2, joint by dorsal ligaments and held by the adductory muscles.
- Marine and freshwater
- Fliter-feeders throught their gills and ciliary action.
Two things involved in filter-feeding in bivalves?
- Ciliary action
- Gills.
What structure of the bivalve is responsible for opening the shell?
The elastic hinge ligament- when the muscles relax the ligaments allows for the valves to open.
What structure is responsible for closing the Bivavles Vavles ?
Adductor muscles
(Important as closing their shells is their main shelf defense)
Prevents valves from tiwisting
Teeth- a series of tongue and groove modification to the shell.
a series of tongue and groove modification to the shell.
(what structure of the bivavle?)
The teeth
The oldest part of the shell.
(what structure is it?)
Umbo
What is a Siphon
Extension of the mantle cavity. Have incurrent and excurrent siphons.
What are gills?
Folded sheets from lamellae.
What adaptations did bivalvia had to help them become great filter feeders?
- Loss of head.
- Loss of radula.
- Extension of ciliated gills.
Outline the steps of gaseous exchange
Water enters the mantle cavity (with organic matter) -> gland cells secret mucus and so OM is covered Water enters the mantle cavity (Organic material + Oxygenated) -> the ciliary tract directs it to -> tiny pores in the gills -> Gland cells secret mucus on particles in suspended water going through the pores of the gill -> water goes to the visceral chambers (water tubes) -> gaseous exchanges occur through diffusion due to blood and water being in close proximity through the water tube.
Outline the process of feeding
Water enters the mantle cavity (with organic matter) -> gland cells secret mucus and so OM is covered in mucus -> Gills trap food -> cilia carry trapped food to the food groove along the ventral margin then move to the mouth -> small food particles move along the food groove to the labia palps -> Labia palps directs food into the mouth. -> larger particles are dropped off into the mantle cavity due to gravitational pull -> ciliary tract on the mantle carries the pseudofeces posteriorly -> pseudofeces forced out when mantle valves shut.
Outline the process of digestion
Food enters the esophagus entangled in a mucoid food string -> winds up around the crystalline style and is pulled into the stomach from the esophagus -> during this, along the stomach pH, food is dislodged into the food string -> fine particles are sent to the digestive gland for intracellular digestion -> ciliary carries undigested waste in the digestive gland, back to the stomach and to the intestine.-> intestine empties into the excurrent opening via the anus -> excurrent water carries the feces away.
