Biology Chapter 12: Phylum Mollusca Flashcards

Questions and Answers

What are the identifying characteristics of mollusks? (Select all that apply)

Most have internal or external shell (correct)

Unsegmented soft body (correct)

Have a radula (correct)

Have a backbone

How is a pearl formed?

A pearl is formed inside of an oyster from sand, water, and other debris.

Can you name examples of animals under Phylum Mollusca?

Clams, Chitons, Squids, Cuttlefish, Octopus, Snails

Why is a Nautilus unique among the cephalopods?

It has numerous slender tentacles and an external coiled pearly shell divided into air-filled chambers. Signup and view all the answers

How does a clam move and what structure does it use?

Clams move using their muscular foot, which is fleshy and located between their shells. Signup and view all the answers

How is jet propulsion used in cephalopod locomotion?

Cephalopods move by filling their muscular mantle cavity with water and quickly expelling it through the siphon. Signup and view all the answers

What is a pneumostome and what is its function?

A pneumostome is an opening in the right side of the mantle of a snail or slug that allows air to enter. Signup and view all the answers

What are the diverse respiratory functions in mollusks?

Aquatic snails or clams breathe using gills inside their mantle cavity. Signup and view all the answers

What is the primary function of the mantle?

To enclose and protect the internal organs. Signup and view all the answers

Describe the circulatory systems in mollusks.

Mollusks may have an open circulatory system that pumps blood between cells or a closed system where blood flows strictly within cells and organs. Signup and view all the answers

How does a pearl form in a bivalve?

The mollusk forms a pearl sac of mantle tissue cells and secretes calcium carbonate to cover the irritant. Signup and view all the answers

What is the function of the radula in cephalopods?

The radula is used for feeding, scraping, or cutting food before it enters the esophagus. Signup and view all the answers

Name examples of Class Cephalopoda.

Octopus, Squid, Nautilus, Cuttlefish, Vampire Squid Signup and view all the answers

Name examples of Class Gastropoda.

Slugs, Snails, Sea hares, Slipper shells, Sea butterflies Signup and view all the answers

Name examples of Class Bivalvia.

Mussels, Oysters, Scallops, Clam Signup and view all the answers

What are the identifying characteristics of Class Cephalopoda? (Select all that apply)

Ink sac Signup and view all the answers

What are the identifying characteristics of Class Bivalvia? (Select all that apply)

Two shells attached from external hinge Signup and view all the answers

What are the identifying characteristics of Class Gastropoda? (Select all that apply)

Muscular foot for movement Signup and view all the answers

Study Notes

Identifying Characteristics of Mollusks

Unsegmented soft body, typically featuring internal or external shells.
Presence of a mantle, a fold in the body wall that secretes protective shells.
Muscular foot and/or tentacles are characteristic features.
Radula: a toothed structure used to grate and obtain food.

Formation of Pearls

Pearls form inside oysters when sand, water, and debris causes irritation.
The mollusk secretes nacre (mother of pearl) layers around the irritant, which builds up over time.

Animal Examples in Phylum Mollusca

Includes clams, chitons, squids, cuttlefish, octopuses, and snails.

Unique Features of Nautilus

Nautilus has numerous slender tentacles and an external coiled pearly shell.
Its shell is divided into air-filled chambers, differentiating it from other cephalopods.

Clam Movement

Clams move using a muscular organ called the foot, located between the two shells.
The foot extends to aid locomotion and is protected by the clam’s shell.

Jet Propulsion in Cephalopods

Octopuses and squids utilize jet propulsion for movement.
They fill the muscular mantle cavity with water and expel it through a siphon, propelling themselves in the opposite direction.

Pneumostome in Snails

Pneumostome: an opening in the mantle of snails/slugs allowing air entry.
Functions as an entrance to a single lung located in the mantle cavity, which is highly vascularized.

Respiratory Functions in Mollusks

Respiratory and circulatory systems lie in the visceral mass.
Aquatic species, like snails or clams, breathe using gills located in the mantle cavity.

Function of the Mantle

Primary role is to enclose and protect internal organs.
Provides space for the mantle cavity, which facilitates respiration and holds air or water.

Circulatory Systems in Mollusks

Mollusks can exhibit open or closed circulatory systems.
Open systems allow blood to move freely between cells and internal tissues.
Closed systems restrict blood flow strictly within vessels, enhancing efficiency.

Pearl Formation in Bivalves

Irritation from an intruder leads bivalves to form a pearl sac from mantle tissue.
Calcium carbonate and conchiolin are secreted around the irritant, forming a pearl over time.

Radula in Cephalopods

Radula: a feeding structure compared to a tongue with tiny teeth.
Used for scraping or cutting food before ingestion through the esophagus.

Examples of Class Cephalopoda

Notable members include octopus, squid, nautilus, cuttlefish, and vampire squid.

Examples of Class Gastropoda

Includes slugs, snails, sea hares, slipper shells, and sea butterflies.

Examples of Class Bivalvia

Features mussels, oysters, scallops, and clams.

Identifying Characteristics of Class Cephalopoda

Features tentacles (8-10 limbs), pigment cells, and an ink sac.
Internal or absent shells, with sophisticated organ systems and eyes similar to human eyes.

Identifying Characteristics of Class Bivalvia

Lack distinct heads or eyes; possess soft bodies and two shells joined by a hinge.
Primarily filter feeders.

Identifying Characteristics of Class Gastropoda

Use a muscular foot for movement and typically have a single retractable shell.
Undergo torsion during larval development, affecting body structure; equipped with a radula.

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Description

Dive deep into the fascinating world of Mollusca with these flashcards. Discover their unique characteristics, such as their unsegmented bodies, shells, and the process of pearl formation. Perfect for students looking to enhance their understanding of this diverse animal group.