Lecture 7

Question 1

What is the largest and most diverse class in Phylum Mollusca?

Answer 1

Class Gastropoda

Question 2

What type of shell is typically found in gastropods?

Answer 2

Univalve shell, which may be coiled or uncoiled

Question 3

What is the term for the twisting of the body plan during gastropod development?

Answer 3

Torsion

Question 4

What are the advantages of torsion in gastropods?

Answer 4

-It allows head to withdraw into shell first for protection
-positions sensory organs toward the front
-ensures clean water enters the mantle cavity

Question 5

What is coiling in gastropods and how is it different from torsion?

Answer 5

Coiling refers to the spiral winding of the shell and visceral mass
Torsion refers to the twisting of the body during development

Question 6

What is Torsion?

Answer 6

the twisting of the body plan during gastropod development

Question 7

What feeding method do most gastropods use?

Answer 7

Most gastropods are herbivores, using a radula to scrape or graze food. Some are scavengers, detritivores, or carnivores, such as the predatory cone snail.

Question 8

How do pulmonate snails respire?

Answer 8

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)

Question 9

What are the key differences between marine snails and terrestrial pulmonates in terms of reproduction?

Answer 9

Marine snails are mostly dioecious with external fertilization, while terrestrial pulmonates are often monoecious with internal cross-fertilization

Question 10

Which informal grouping of gastropods contains organisms with torsion and typically has a single gill?

Answer 10

Prosobranchs

Question 11

Which class of mollusks includes clams, oysters, mussels, and scallops?

Answer 11

Class Bivalvia

Question 12

What is the main adaptation that bivalves have for a sedentary, filter-feeding lifestyle?

Answer 12

Loss of the head and radula, and expansion of cilia-covered gills for filter feeding

Question 13

How do bivalves use their gills (ctenidia) for feeding and gas exchange?

Answer 13

The gills trap food particles from the water for filter feeding and also facilitate gas exchange

Question 14

What is the role of the crystalline style in bivalve digestion?

Answer 14

It rotates in the stomach to help grind food and release digestive enzymes

Question 15

What specialized larval form do freshwater clams produce for reproduction?

Answer 15

Glochidium, a larval form that hitchhikes on fish for dispersal

Question 16

Which class of mollusks includes octopuses, squids, cuttlefish, and nautiluses?

Answer 16

Class Cephalopoda

Question 17

What is the main method of locomotion in cephalopods?

Answer 17

Jet propulsion, achieved by forcing water out of the siphon

Question 18

How do cephalopods achieve greater efficiency in respiration compared to other mollusks?

Answer 18

They have a closed circulatory system with increased blood pressure, branchial hearts, and a higher rate of water circulation through gills

Question 19

What is the function of chromatophores in cephalopods?

Answer 19

Chromatophores allow cephalopods to change color and patterns for communication, camouflage, and defense

Question 20

What specialized tentacle is used by male cephalopods during reproduction? what does it do?

Answer 20

The hectocotylus; transfers spermatophores to the female

Question 21

How do cephalopods care for their eggs?

Answer 21

Eggs are attached to substrates like the ceiling of an octopus’s den, cleaned of debris, and tended until they hatch as miniature adults

Question 22

What terms describe the orientation of gastropod shells?

Answer 22

Dextral and Sinistral

Question 23

What is meant by Dextral (pertaining to shell orientation)?

Answer 23

Right-Handed

Question 24

What is meant by Sinistral (pertaining to shell orientation)?

Answer 24

Left-Handed

Question 25

What is the function of the operculum in gastropods?

Answer 25

It acts as a protective cover, closing the opening of the shell when the foot is withdrawn

Question 26

What anatomical feature opens to the outside in pulmonate snails to allow air into their lungs?

Answer 26

The pneumostome

Question 27

What structure in the bivalve stomach helps move food for digestion?

Answer 27

The rotating mucous-food cord in the esophagus

Question 28

What type of symbiosis is found in giant clams?

Answer 28

Symbiosis with zooxanthellae, which live within their tissues

Question 29

How do octopuses differ from other cephalopods in terms of locomotion?

Answer 29

Octopuses are more sedentary and use tentacles for movement, relying on jet propulsion only for quick escape

Question 30

How do cephalopod eyes differ from vertebrate eyes?

Answer 30

In cephalopods, the optic nerves leave the eye outside the eyeball, unlike in vertebrates

Question 31

What structural feature supports the body in cephalopods like squids and cuttlefish?

Answer 31

Cartilaginous plates in the mantle, neck, and head provide support and protection

Question 32

What is Torsion?

Answer 32

Developmental process in which the body twists and positions the mantle cavity and anus over the head; providing protection and access to sensory information

Question 33

What are Prosobranchs?

Answer 33

Group of Gastropods that have their gills, anus, and nephridia in front of their heart due to torsion

Question 34

What are Opisthobranchs?

Answer 34

Group of Gastropods that are characterized by detorsion (absense of torsion)
- has reduced or absent shell

Question 35

What is a Glochidium

Answer 35

A larval stage found in some freshwater bivalves
- they hitchhike on fish gills / fins to disperse to new habitats

Question 36

What is a Hectocotylus

Answer 36

A reproductive arm in male cephalopods that transfers spermatophores to female during mating

Question 37

What is a Siphuncle

Answer 37

A tube-like structure in shell of nautiloids and ammonoids
- regulates gas and fluid within the shell chambers
-helps maintain buoyancy

Question 38

What is the ink-like substance secreted by cephalopods as a defense mechanism (to confuse predators)

Answer 38

Sepia