Mollusca (6,7) Flashcards
What is the largest and most diverse class in Phylum Mollusca?
Class Gastropoda
What type of shell is typically found in gastropods?
Univalve shell, which may be coiled or uncoiled
What is the term for the twisting of the body plan during gastropod development?
Torsion
What are the advantages of torsion in gastropods?
-It allows head to withdraw into shell first for protection
-positions sensory organs toward the front
-ensures clean water enters the mantle cavity
What is coiling in gastropods and how is it different from torsion?
Coiling refers to the spiral winding of the shell and visceral mass
Torsion refers to the twisting of the body during development
What is Torsion?
the twisting of the body plan during gastropod development
What feeding method do most gastropods use?
Most gastropods are herbivores, using a radula to scrape or graze food. Some are scavengers, detritivores, or carnivores, such as the predatory cone snail.
How do pulmonate snails respire?
Pulmonates lack gills and use a vascularized area of the mantle, called the pulmonate lung for respiration.
(They open to the outside via the pneumostome)
What are the key differences between marine snails and terrestrial pulmonates in terms of reproduction?
Marine snails are mostly dioecious with external fertilization, while terrestrial pulmonates are often monoecious with internal cross-fertilization
Which informal grouping of gastropods contains organisms with torsion and typically has a single gill?
Prosobranchs
Which class of mollusks includes clams, oysters, mussels, and scallops?
Class Bivalvia
What is the main adaptation that bivalves have for a sedentary, filter-feeding lifestyle?
Loss of the head and radula, and expansion of cilia-covered gills for filter feeding
How do bivalves use their gills (ctenidia) for feeding and gas exchange?
The gills trap food particles from the water for filter feeding and also facilitate gas exchange
What is the role of the crystalline style in bivalve digestion?
It rotates in the stomach to help grind food and release digestive enzymes
What specialized larval form do freshwater clams produce for reproduction?
Glochidium, a larval form that hitchhikes on fish for dispersal
Which class of mollusks includes octopuses, squids, cuttlefish, and nautiluses?
Class Cephalopoda
What is the main method of locomotion in cephalopods?
Jet propulsion, achieved by forcing water out of the siphon
How do cephalopods achieve greater efficiency in respiration compared to other mollusks?
They have a closed circulatory system with increased blood pressure, branchial hearts, and a higher rate of water circulation through gills
What is the function of chromatophores in cephalopods?
Chromatophores allow cephalopods to change color and patterns for communication, camouflage, and defense
What specialized tentacle is used by male cephalopods during reproduction? what does it do?
The hectocotylus; transfers spermatophores to the female
How do cephalopods care for their eggs?
Eggs are attached to substrates like the ceiling of an octopus’s den, cleaned of debris, and tended until they hatch as miniature adults
What terms describe the orientation of gastropod shells?
Dextral and Sinistral
What is meant by Dextral (pertaining to shell orientation)?
Right-Handed
What is meant by Sinistral (pertaining to shell orientation)?
Left-Handed
What is the function of the operculum in gastropods?
It acts as a protective cover, closing the opening of the shell when the foot is withdrawn
What anatomical feature opens to the outside in pulmonate snails to allow air into their lungs?
The pneumostome
What structure in the bivalve stomach helps move food for digestion?
The rotating mucous-food cord in the esophagus
What type of symbiosis is found in giant clams?
Symbiosis with zooxanthellae, which live within their tissues
How do octopuses differ from other cephalopods in terms of locomotion?
Octopuses are more sedentary and use tentacles for movement, relying on jet propulsion only for quick escape
How do cephalopod eyes differ from vertebrate eyes?
In cephalopods, the optic nerves leave the eye outside the eyeball, unlike in vertebrates
What structural feature supports the body in cephalopods like squids and cuttlefish?
Cartilaginous plates in the mantle, neck, and head provide support and protection
What is Torsion?
Developmental process in which the body twists and positions the mantle cavity and anus over the head; providing protection and access to sensory information
What are Prosobranchs?
Group of Gastropods that have their gills, anus, and nephridia in front of their heart due to torsion
What are Opisthobranchs?
Group of Gastropods that are characterized by detorsion (absense of torsion)
- has reduced or absent shell
What is a Glochidium
A larval stage found in some freshwater bivalves
- they hitchhike on fish gills / fins to disperse to new habitats
What is a Hectocotylus
A reproductive arm in male cephalopods that transfers spermatophores to female during mating
What is a Siphuncle
A tube-like structure in shell of nautiloids and ammonoids
- regulates gas and fluid within the shell chambers
-helps maintain buoyancy
What is the ink-like substance secreted by cephalopods as a defense mechanism (to confuse predators)
Sepia
What is a Coelom?
A body cavity in animals that provides space for internal organs and is used for functions like movement and organ development
What is the body cavity in animals that provides space for internal organs and is used for functions like movement and organ development
the Coelom
