Lecture 10 - Mollusks I Flashcards

1
Q

Phylum Mollusca:

A

Free-living invertebrates with an unsegmented, soft body consisting of a visceral mass, foot, mantle, gills, and usually a hard, calcareous, univalved or bivalved shell.

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2
Q

Three Important Classes of Phylum Mollusca:

A

Class Gastropoda
Class Pelecypoda
Class Cephalopoda

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3
Q

Class Gastropoda:

A

Snails, Slugs, & Pteropods

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4
Q

Class Gastropoda Geologic Range

A

Upper Cambrian to Recent

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5
Q

Class Pelecypoda:

A

Clams, Oysters, Scallops, & Mussels

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6
Q

Class Pelecypoda Geologic Range

A

Lower Cambrian to Recent

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7
Q

Class Cephalopoda:

A

Octopus, Squid, Nautiloids, & Ammonoids

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8
Q

Class Cephalopoda Geologic Range

A

Upper Cambrian to Recent

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9
Q

Visceral Mass:

A

Main part of the body containing the vital internal organs

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10
Q

Foot:

A

Muscular organ extending from the visceral mass; it is modified in various molluscan groups as a structure used in swimming, crawling, and/or burrowing.

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11
Q

Gills:

A

Sheets or filaments of blood-filled tissue that serve as respiratory organs.

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12
Q

Mantle:

A

Sheet of tissue that secretes the shell and lines the inside of the shell.

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13
Q

Siphon:

A

Fold in the mantle forming a tubular structure for bringing water into the mantle cavity.

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14
Q

Radula:

A

Rasping, tongue-like structure in the mouth of some mollusks (found in gastropods, cephalopods, & polyplacophores, but not in pelecypods); it is lined with tiny, sharp, tooth-like hard parts for scraping and/or drilling.

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15
Q

Molluscan Shell Composition:

A

Conchiolin (organic material composing the periostracum on the shell surface)
Calcite (may be pure calcite, or else low-Mg or high-Mig calcite)
Aragonite

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16
Q

Molluscan Shell Microstructure:

A

Prismatic, Foliated, Nacreous

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17
Q

Prismatic:

A

Layer consisting of tiny, vertical prisms of calcite or aragonite

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18
Q

Foliated:

A

Layer consisting of imbricated plates of calcite.

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19
Q

Nacreous (“mother-of-pearl”):

A

Interlaminated sheets of aragonite and organic conchiolin.

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20
Q

Mollusscan Shell Shape:

A

Planispiral, Conispiral

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21
Q

Planispiral:

A

Coiled in a single plane (e.g., nautiloids & ammonoids)

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22
Q

Conispiral:

A

Coiled along a translating axis to form a cone (e.g., gastropods)

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23
Q

Apex:

A

Pointed end of the shell

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24
Q

Aperture:

A

Opening in the end of the shell opposite the apex.

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25
Radial Ribs:
Raised ridges that radiate from the apex towards the aperture.
26
Growth Rings:
Ring-like ridges that parallel the aperture and represent shell growth.
27
Spines:
Long, sharp projections on the shell exterior.
28
Nodes:
Short, blunt projections on the shell exterior.
29
Class Gastropoda:
Mollusks with a distinct head that usually possesses eyes and sensory tentacles; mouth possesses a radula; foot adapted for crawling in most forms, but is adapted for swimming or burrowing in some forms; nervous system of head & body are distinct; heart has 2 or 3 chambers; general bilateral symmetry, which is secondarily reorganized during ontogeny by "torsion"; most (but not all) members of the class have a single, univalved, conispiral shell with one aperture; the shell is always composed of aragonite; 3 very diverse subclasses
30
Class Gastropoda Geologic Range
Cambrian to Recent
31
Three main subclasses of Class Gastropoda:
``` Subclass Prosobranchia Subclass Opisthobranchia Subclass Pulmonata ```
32
Subclass Prosobranchia:
Gastropods with gills in front next to head; a robust, external, conispiral shell; commonly have an operculum; very good fossil record
33
Subclass Prosobranchia Geologic Range
Upper Cambrian to Recent
34
Three main orders of Subclass Prosobranchia
Order Archaeogastropoda Order Mesogastropoda Order Neogastropoda
35
Order Archaeogastropoda:
Two gills; 3-chambered heart; no inhalent siphon; shell has a circular or oval aperture; mainly herbivores; mostly marine (a few fresh-water species)
36
Order Archaeogastropoda Geologic Range
Upper Cambrian to Recent
37
Order Mesogastropoda:
One gill; 2-chambered heart; well-developed siphon; shell typically has a siphonal notch; includes herbivores, scavengers & predators; exclusively marine
38
Order Mesogastropoda Geologic Range
Lower Ordovician to Recent
39
Order Neogastropoda:
One gill; 2-chambered heart; well-developed siphon; shell typically has a siphonal canal; highly specialized predators; exclusively marine
40
Order Neogastropoda Geologic Range
Upper Jurassic to Recent
41
Subclass Opisthobranchia:
Advanced marine gastropods with gills behind head; either a very thin, internal shell or no shell at all; most are active predators; exclusively marine; typically a very poor fossil record
42
Subclass Opisthobranchia Geologic Range
Middle Devonian to Recent
43
Subclass Pulmonata:
Advanced terrestrial gastropods with either a thin external shell or no shell at all; mantle adapted for breathing in air; mainly herbivores; continental environments; a very spotty fossil record found only in terrestrial sediments
44
Subclass Pulmonata Geologic Range
Pennsylvanian to Recent
45
Visceral Mass:
Torsion brings the stomach up and over the head
46
Foot:
Muscular organ modified mainly for crawling, but also for swimming and/or burrowing.
47
Gills:
Leaf-shaped structures of blood-filled tissue that serve as respiratory organs.
48
Mantle:
Tissue that lines inside of shell of prosobranchs or envelopes shell of opisthobranchs.
49
Siphon:
Fold in the mantle forming a single inhalent tube.
50
Radula:
Rasping, tongue-like structure in the mouth of all gastropods.
51
Protoconch:
Earliest portion of the shell, located at the apex.
52
Whorl:
One complete revolution of the conispiral shell.
53
Columella:
Pillar of shell material at the axis of coiling of the shell.
54
Aperture:
Large opening in the shell through which the foot protrudes.
55
Callus:
Thickened region of the shell along the inside margin of the aperture.
56
Lip:
Thickened region of the shell along the outside margin of the aperture.
57
Operculum:
Calcareous or chitinous "door", which seals off the aperture when the foot retracts.
58
Anal Slit:
Notch in the lateral side of the aperture (only in pleurotomariids & some primitive limpets) to accommodate excretion from the anus.
59
Anal Aperture:
Second opening in apex of some limpets to accommodate excretion from the anus.
60
Siphonal Notch:
Notch in the anterior end of the aperture of most mesogastropods to allow the siphon to protrude.
61
Siphonal Canal:
Groove-like or tubular extension of the notch in the anterior end of the aperture of most neogastropods to conceal and protect the long siphon as it protrudes.
62
Ornamentation:
Ribs, spines, nodes, etc., on the exterior of the shell.