Mollusca 1

Question 1

Intro

3 points

Answer 1

1. Second largest phylum
2. Large degree of morphological diversity
3. Occupy all major habitat types

Question 2

Classification

Answer 2

Kingdom: metazoa

Phylum: Mollusca

8 Classes: 
Caudofoveates, 
Salanogastes, 
Chitons, 
Monoplacophora, 
Scaphopods, 
Bivalves (most), 
Gastropods (most), 
Cephalopods

Question 3

3 most universal features defining modern molluscs

Answer 3

1. mantle with a significant cavity used for breathing and excretion
2. presence of a radula (except for bivalves)
3. structure of the nervous system.

Question 4

Visceral =

Answer 4

Collection of tissues joined in unit for common functionality

Question 5

Radula –

Answer 5

anatomical structure used for feeding.

Question 6

Key characteristics

Answer 6

1. Buccal region with radula, ribbon like, heavily modified.
2. Through gut (complete, regional specialisation) and kidneys
3. Gas exchange by ctenidial gills housed in mantle cavity
4. Separate sexes (dioecious)
5. Trochophore and veliger larva

Question 7

Body structure

Body wall recognisable layers

3 points

Answer 7

1. cuticle, epidermis (ciliated) and muscles
2. Mantle and mantle cavity (water contact)
3. Ctenidia (Ctenidial gills)
   Central flattened longitudinal axis
   Triangular filaments (alternate along longitudinal axes)
   Water driven between filaments by cilia

Question 8

Body structure

Calcareous shell

5 points

Answer 8

1. Most solid shell (aragonite calcite)
2. Shell glands in mantel
3. Calcium carbonate layered
4. Thin organic surface coating
5. Multiple/Single/internal/no shells

Question 9

Body structure
Torsion
6 points

Answer 9

1. Occurs during development in all gastropods
   During late veliger larval stage
2. Rotation of the visceral mass, mantle and shell
3. Anticlockwise direction
4. Two-step process
   First rapid 90° twist
   Slower second 90° twist (tissue growth)
5. Torted or detorted
6. Gastropod: one aperture in shell

Question 10

Locomotion

5 points

Answer 10

1. Crawling
2. Burrowing
3. Boring
4. Swimming
5. Sedentary/sessile
   Byssal threads

Question 11

Feeding

radula 3 points

Answer 11

1. Radula membrane
   Radular protractor and retractor muscles

2.Radula sac

3. Odontophore
   Hard calcareous structure
   Odontophore protractor and retractor muscles

Question 12

Feeding

2 points

Answer 12

1. Macrophagy
   Herbivores
   Predators
   Scavengers
2. Microphagy
   Suspension feeders
3. most vegetarians

Question 13

Reproduction

5 points

Answer 13

1. Sexual
2. Dioecious
3. External fertilisation
   Indirect development
   Trochophore larva
   Veliger larva (velum)
4. Internal fertilisation
   Direct and mixed development
   Egg brooding
5. Hermaphrodites

Question 14

Chromatophores

3 points

Answer 14

1. pigment-containing and light-reflecting cells
2. Controlled by nervous system
3. Expanded and contracted by muscle cells

Question 15

ink sacks

4 points

Answer 15

1. Located near intestine
2. Dark fluid containing melanin pigment
3. Alarm response, blinding attackers.
4. Used in contract to bioluminescence in permanently dark environments,

Question 16

highly divergent grouo

Answer 16

squids clams and slugs

Question 17

most advanced

Answer 17

squids and cuttlefish

Question 18

diversity in molluscs - hypothetical generalised mollusc used to illustrate

4 points

Answer 18

1. bilaterally symmetrical
2. single “limpet-like” shell (secreted by mantle
   covering the upper surface)
3. The underside is a muscular
   “foot”.
4. The visceral mass, is the non-muscular metabolic region
   containing the body organs

Question 19

extinction

Answer 19

1. 2 families extinct

2. various molluscs brink of extinction