Midterm 1

Phylum Mollusca Diversity

Second most diverse phylum in described species, first in the ocean.

Mollusca Development & Tissue Layers

Exhibits protostome development, external cilia, and three tissue layers.

Mollusca Fossil Record

Dates back approximately 530 million years ago.

Mollusca Symmetry

Bilaterally symmetrical, except in some gastropods.

Mantle Function

Covers the body and secretes the calcium carbonate shell.

Molluscan Foot

Used for locomotion and modified in various ways.

Class Gastropoda Members

Includes snails, limpets, land slugs, and sea slugs.

Gastropod Shell Count

Typically one shell in adults; some slugs have none.

Radula

A ribbon of rows of teeth used for scraping or drilling.

Torsion

A 180-degree twisting of the body during gastropod development.

Gastropod Shell Composition

Made of calcium carbonate and protein, covered with periostracum.

Land Snails Respiration

Gills are replaced with a lung made of a modified mantle cavity.

Class Bivalvia Members

Commercially important clams, mussels, scallops, and oysters.

Bivalve Shells

Two equal or nearly equal shells called valves.

Bivalve Locomotion & Attachment

Foot is used for burrowing or attaching via byssus threads.

Bivalve Feeding Method

Filter feeders using gills to draw water and capture particles.

Bivalve Particle Sorting

Labial palps sort particles; non-food is expelled as pseudofeces.

Crystalline Style

An anterior structure in the bivalve digestive tract that aids digestion.

Bivalve Cephalization

No head or radula present; three pairs of ganglia control functions.

Class Cephalopoda Members

Includes squid, cuttlefish, octopuses, and the chambered nautilus.

Cephalopod Foot Modification

Modified and divided into many arms.

Cephalopod Jaws

Highly specialized beak accompanied by a radula.

Class Polyplacophora (Chitons)

Features eight overlapping shell plates held by a girdle.

Aesthetes

Sensory eyes distributed across the shell of chitons.

Class Scaphopoda Shell

A tubular shell that is open at both ends.

Class Monoplacophora Shell

Cap-like or coiled shell with many fossil representatives.

Aplacophora Characteristics

Worm-like body with shell reduced or absent as free spicules.

Haliotis (Abalone) Fertilization

External fertilization with no copulating organs or sexual dimorphism.

Haliotis Larval Stages

Trochophore stage swims for 2-3 days, followed by the veliger stage.

Nucella (Dogwhelk) Reproduction

Dioecious species that reproduces via copulation

Terrestrial Snail Reproduction

Simultaneous hermaphrodites that undergo copulation with mutual fertilization.

Helix Development

Direct development with no larval stage.

Pearl Formation

Mantle coats an irritant with layers of nacre.

Cultured Pearl Induction

Inserting a shell nucleus and mantle tissue into a pearl oyster.

Class Scyphozoa Composition

Gelatinous zooplankton consisting of approximately 97% water.

Atoll Formation Step 1

Fringe coral reefs form around a sinking volcanic island.

Atoll Formation Step 2

Corals grow upward as the island completely sinks below sea level.

Mollusk Circulatory System

Open circulatory system utilizing hemocyanin or hemoglobin to transport oxygen.

Osphradium

A chemoreceptor organ in the molluscan nervous system.

Statocyst

A sensory organ that helps orient the molluscan foot.

Phylum Bryozoa

Colonial organisms composed of very small, erect branching zooids.

Bryozoan Feeding

Filter feeders using a ring of rapidly retractable tentacles.