Molluscs

Question 1

What is a coelom? And why is it important for evolution

Answer 1

A coelom is a fluid filled cavity that contains the animals internal organs. It was important for evolution as it helped development of blood vessel networks, a suspended alimentary canal and led to more complex body forms

Question 2

What is special about the molluscan coelom?

Answer 2

It is reduced in size, which also led to a reduced important. It is called the pericardial cavity

Question 3

Briefly name and state the use of the two main regions in molluscs

Answer 3

Head-Foot- Feeding, sensory and locomotion
Visceral mass - Digestive, circulatory, respiratory, reproductive

Question 4

What is a radula?

Answer 4

A rasping, protruding tongue like organ
too many teeth (250 000)
not present in bivalves

Question 5

What is the importance of the odontophore?

Answer 5

Movement of the radula

Question 6

What is the function of a radula in molluscs?

Answer 6

Rasps fine particles of food from hard surfaces
Carries particles to the digestive tract like a conveyor belt

Question 7

List 2 examples of foot modifications in molluscs

Answer 7

Snails - creeping motion
limpets, chitons - Attachment
Bivalves - Hatchet foot
Squids, octopuses - Siphon tentacles and head
Sea hares/butterflies - swimming

Question 8

What is the mantle and mantle cavity?

Answer 8

Mantle is the sheet of skin that drapes over soft body parts
The mantle cavity is the space between the mantle and visceral mass which houses respiratory organs

Question 9

Which mollusc class has a closed circulatory system?

Answer 9

Cephalopods

Question 10

What are ctenidia in molluscs

Answer 10

Gills - kinda in the mantle cavity
ciliated and leaf like
very efficient, uses countercurrent

Question 11

What are the 3 layers of a mollusc shell

Answer 11

periostracum
Prismatic layer
Nacreous layer

Question 12

What are some features of the periostracum in molluscs

Answer 12

Outer organic layer, protects other layers and is composed of conchiolin

Question 13

What are some features of the Prismatic layer in molluscs

Answer 13

Made of densely packed calcium carbonate prisms

Question 14

What are some features of the nacreous shell layer in molluscs

Answer 14

Continuously secreted by and lays beside the mantle
pearls i think

Question 15

Summarize mollusc class gastropoda

Answer 15

Largest and most diverse class
Marine, freshwater and terrestrial, Univalve shell

Question 16

What is the name for the right and left handed shells

Answer 16

Dextral, and sinistral respectively

Question 17

What are the advantages of torsion in gastropods

Answer 17

Allows for the head to be drawn in before the foot for protection
Helps clean water be brought in
Sensory organs are anterior to the head, improving stimuli sensitivity

Question 18

What is the difference between coiling and torsion in gastropods

Answer 18

Coiling is spiralized
Effects different parts of the body
Coiling allows for more space, whereas torsion moves the organs

Question 19

How can the radula be used for feeding?

Answer 19

It can be used to scrape things, tear, drill and can even evolve to be weaponzied

Question 20

Are marine snails mono or di oecious

Answer 20

Dioecious, they fertilize externally into the water

Question 21

Name 3 ways monoecious snails reproduce

Answer 21

Mutual sperm transfer, They choose a sex, or eggs are deposited in gelatinous strings or masses

Question 22

What is the torsion larvae called in gastropods?

Answer 22

Veliger larve

Question 23

Summarize gastropod subclass prosobranchia

Answer 23

Has torsion, Separate sexes, mainly marine snails

Question 24

Summarize gastropod subclass opisthobranchia

Answer 24

Sea slugs, limited or no torsion, monoecious, little to no shell present

Question 25

Summarize gastropod subclass pulmonata

Answer 25

Land snails, monoecious,no gills, no torsion (detorted), anatomically are more advanced

Question 26

Summarize class bivalvia

Answer 26

Aquatic, clams, oysters, mussels and scallops
They burrow and attach to substrates, bore into wood and coral
Adapted to a sedentary filter feeding lifestyle
No head or radula, expansion of cilia-covered gills

Question 27

How have gills and mantle adapted for gas exchange in bivalves

Answer 27

Wider surface area as they have morphed into a W shape
The visceral mass hangs down from the midline and connects to the gills

Question 28

In cephalapods, what was modified into the tetacles?

Answer 28

The anterior margin of the foot

Question 28

How does reproduction work in bivalves?

Answer 28

Most are dioecious but not all, typically external fertilization, some have specialized development

Question 29

How was the shell modified in cephlapods?

Answer 29

In octopuses it is absent, squid and cuttlefish have it internally

Question 30

How does jet propulsion occur in cephlapods?

Answer 30

Mantle muscles bring water in, and then circular muscles contract which forces the water out pushing it. Siphon muscles control direction

Question 31

What are chromatophores?

Answer 31

Pigment cells that allow for changes in colours and patterns, each one has tiny muscles that allow for changes

Question 32

Are cephalopods mono or di oecious?

Answer 32

Dioecious