Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Marine Invertebrates SOES1007 > Molluscs > Flashcards

Molluscs Flashcards

0
Q

Where are the molluscs found and how many species are there?

A

They are found in the sea, in freshwater and on land with ~100k spp.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What are Molluscs?

A

A major radiation of the metazoans. The name means soft bodied.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where did molluscs originate?

A

They have a marine origin and are an ancient phylum which can be traced back to the precambrian. The earliest molluscs are the Helliconellida (540Mya)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the basic Molluscan body plan?

A

+A shell, usually CaCO3
+A mantle - holds everything together.
+A circum-oesophageal ring - the ‘brain.’
+Mouth, containing radula.
+Digestive gland, where enzymes are collected.
+An open circulation system.
+An excretory organ where nitrogenous waste/ammonia is removed
+Gills

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the circulatory system of a mollusc like?

A

The heart contracts and pumps haemolymph to areas that require high blood pressure, like the excretory system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the size range in the mollusca like?

A

1mm->9m.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is molluscan taxonomy like?

A

The mollusca are polyphyletic - all groups do NOT share an immediate common ancestor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the main classes, subclasses and orders contained within the Mollusca?

A

Bivalvia (scallops, clams, mussels etc.)
Monoplacophora (limpet-like ‘living fossils’)
Gastropoda (snails, slugs, limpets, sea hares)
Cephalapoda (squids, octopuses, nautilus, ammonites)
Scaphopoda (tusk shells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the Aculifera?

A

A group of organisms:
Aplacophora (spicule covered worm like animals)
Polyplacophora (chitons)
Commonality of ancestry so far back that they have little in common. Argued they could have their own phyla.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the Aplacophora?

A

Aculiferan molluscs, classified as such due to their radula and other molluscan characteristics in internal anatomy.
They have spicules in the outer layer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two classes of Aplacophora?

A

The Chaetodermomorpha: wormlike burrowers with spicule-reinforced outer layer.
The Neomeniomorpha: they have a creeping foot-like ridge. They are unsegmented.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the Polyplacophora?

A

Name means ‘many plates.’
Chitons are an ancient exclusively marine group.
Shell consists of eight interlocking hinged plates, with a fringe of spines or spicules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the function of the spines or spicules in the Polyplacophora?

A

The plates deter predators attacking from the top, so the spines or spicules are there to deter predators from attacking from the side.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the Monoplacophora?

A

Shell consists of single cone of material. Discovered in 1952. 10spp now known. They are deep sea.
Paired arrangements of gills and gonads are replicated, not evidence of vestigial segmentation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the Gastropoda?

A

Name means ‘stomach foot.’
Soft tissues covered by a single shell, usually tubular and coiled on itself. Where external shell has been lost, vestigial structures are found in the soft tissues.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is gastropod torsion?

A

Within the soft tissues there is torsion, i.e. the movement of the mantle cavity to the front of the animal. Partial de-torsion may occur in later stages of development. IT IS UNRELATED TO SHELL COILING.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does gastropod torsion achieve?

A

It improves irrigation but also excretes waste over face.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the three taxa within the gastropods?

A

The Prosobranchiata: gills at the front.
The Opisthobranchiata: gills to the rear after de-torsion.
The Pulmonata: gills lost and mantle cavity functions as simple lung for life in air. Mainly freshwater and terrestrial.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the Prosobranchiata like?

A

A very diverse group of mostly marine spp. Mantle cavities at the front. Shell provides protection against predators. They start small and add tissue to front of shell as they grow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the operculum?

A

A piece of tissue that can be used to shut of the aperture for complete protection in the case of a predator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the Opisthobranchiata?

A

Sea slugs and sea hares. Majority have lost their shell. Some have external gills but with unpleasant tasting toxins. Some have cerata containing nemocytes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the Pulmonata?

A

Terrestrial and freshwater. Snails and slugs. Mantle cavity on the side of the slug.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the Bivalvia?

A

Typically a bivalve shell is two calcareous valves enclosing a visceral mass. The soft tissues are kept in the pallial sinus. Usually sedentary, but exceptions are scallop swimming escape response and Lasaea rubra, bivalve that glides through lichen ‘turf’ in the supralittoral.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Do bivalves have teeth?

A

Yes! They are used to stop the shell from shifting when it is closed.

24
Q

What are the Scaphopoda?

A

Small exclusively marine group living in soft sediments. Tubular shell open at both ends.

25
Q

What are the Cephalopods?

A

Active marine carnivores with an advanced nervous system and sense organs. Approx. 900 living spp but an extensive fossil record available.

26
Q

What is the Cephalopod brain like?

A

It is circum-oesophageal so still has oesophagus running through it. Huge areas for optic processing.

27
Q

What is Cephalopod taxonomy like?

A

There are two living sub-classes of cephalopods & at least three sub-classes of extinct forms identifiable from the fossil record. It is one of the most contentious and fluid areas of molluscan taxonomy.

28
Q

What are the two extant sub-classes of Cephalopods?

A

The Nautiloidea and the Coleoidea.

29
Q

What are the Nautiloidea?

A

Nautiloids. Coiled external shell. Only a small number of living representatives (Nautilus spp).

30
Q

What are the Coleoidea?

A

Cuttlefish, squid and octopuses. Shell internal and reduced or lost. Fast swimmers using water squirted from the mantle cavity.

31
Q

What are the two theories on the molluscan shell evolved?

A

The Aculiferan hypothesis and the Testarian hypothesis.

32
Q

What is the Aculiferan hypothesis?

A

It is development from an ancestral form that reinforced its outer layer with calcareous spicules cf Chaetoderma.

33
Q

What is the Testarian hypothesis?

A

The molluscan shell developed from a mucus coating, that first became stiffened into a cuticle. Eventually the cuticle would have become mineralised, using the same genetic machinery (engrailed) as most other bilaterian skeletons - able to take up CaCO3 as bicarbonate from seawater.
NB: a cuticle or shell are impermeable so their development would have forced the evolution of more efficient respiratory systems.

34
Q

What are the main functions of the Molluscan shell?

A

Protection against predators and harmful external conditions (e.g. salinity changes/desiccation)
Structural rigidity.

35
Q

What can the Molluscan shell be modified to do?

A 
Aid feeding
Provide bouyancy (cuttlefish & Nautiloids)
Compensate for external conditions.
36
Q

How are Molluscan shells formed?

A

During shell formation CaCO3 is laid down mainly as aragonite, though some calcite is found in the prismatic layer of some species.
The periostracum and the protein binding within the shell layers is formed of the protein conchiolin.

37
Q

What are the three layers of a Molluscan shell?

A

The periostracum, the prismatic layer and the nacreous layer(s).

38
Q

What is the nacreous layer’s function?

A

It’s pearlescent, so it allows soft tissues to move against the shell without abrasion. It’s made of flat plates of aragonite.

39
Q

What is the layering of the layers of the shell like?

A

They layering of the prismatic layer is perpendicular to that of the nacreous layer, to prevent any cracks from entering the nacreous layer.

40
Q

How and why are pearls formed in the Molluscan shell?

A

Pearl formation is a response to the presence of foreign material between the nacreous layer and the soft tissues of the mantle. The inflammation response causes the deposition of successive layers of nacre to isolate the irritant.

41
Q

How is the shell a buoyancy organ in Nautiloids?

A

In nautiloids the many-chambered shell largely is gas-filled. When first formed, each chamber is filled with seawater that is withdrawn by the active transport of salts into the siphuncle, causing water to follow and gas to come out of solution as the loss of water lowers the pressure inside the chamber.

42
Q

For what depth is the buoyancy adjusted in Nautiloids?

A

~200m.

43
Q

How is the shell a buoyancy aid in Cuttlefish?

A

The cuttlebone of sepiids is composed of pillar-like aragonite crystals, so that the structure is honeycombed with gas and fluid-filled spaces, created by a process similar to that seen in nautiloids.

44
Q

What are the organ systems in cephalopods like?

A

The evolution of a non-segmented body in molluscs has produced body forms with well-developed organ systems and associated physiology that allows major increases in size and levels of activity.
All molluscs have an advanced circulatory system and kidney like systems which require high blood pressure.

45
Q

What did the development of a circulatory system in molluscs achieve?

A

The development of a circulatory system increased the efficiency of respiratory and excretory systems.

46
Q

How do most molluscs feed?

A

The radula is the main feeding organ in molluscs. It has been adapted to several types of feeding that range from rasping of algal films, filter feeding and active predation.
Other body parts e.g. gills and foot have become secondarily adapted.

47
Q

What are some other feeding mechanisms in molluscs?

A

Cilia in gills adapted to link together and form sieve-like system, feeding into mucous trails that link to mouth.
Photosynthesis.
Cone shells adapt salivary glands for poison.
Aesthetes in giant clam detect light and cause it to shut.

48
Q

What is locomotion in molluscs like?

A

The foot is the primary locomotory organ in molluscs that are not sessile as adults. It is divided into three parts.

49
Q

What are the three parts of the molluscan foot?

A

The propodium, the mesopodium and the metapodium.

50
Q

What does the propodium do?

A

It is the front. It is extensible and exploratory.

51
Q

What is the mesopodium?

A

The bottom. It’s muscular, powerful with finely controllable waves of contraction.

52
Q

What is the metapodium?

A

The back. It carries the operculum in gastropods.

53
Q

What is the nervous system & the sense organs of the molluscs like?

A

They all have a circum-oesophageal ganglion, but there’s enormous variation in complexity of molluscan nervous systems. Some have chemosensory structures whereas others have simple eyes to the very complex eyes of the octopus.

54
Q

How do molluscs reproduce?

A

There is a broad range of strategies ranging from broadcast spawners to internal fertilisation. However:
+There is a tendency to hermaphroditism (particularly sessile/slow moving spp)
+Internal fertilisation in many groups (ensures fertilisation)
+Suppression of larval stage and encapsulation.
+Degree of parental care in some advanced forms.

55
Q

What is a siphuncle and what is its function?

A

A thin strand of tissue containing a blood space that connects the chamber in a nautiloid & is used in the secretion of gas into the chamber.

56
Q

What are the functions of the three hearts in cephalopods?

A

One main heart for general circulation and one at the base of each gill to increase gas exchange efficiency.

57
Q

How do bivalves feed?

A

Filter feeding using their gills.

58
Q

What is the final planktonic stage in most bivalves gastropods?

A

A veliger with a large ciliated velum.

Marine Invertebrates SOES1007 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions