Phylum Mollusca (Class Gastropoda and Bivalvia) Flashcards

For Zoology

What does HAM stand for?

Hypothetical Ancestral Mollusc

Describe HAM

A hypothetical primitive ancestor that appear among most members of the mollusca

Describe the foot

A broad, flat muscular organ that is adapted for locomotion and attachment

Describe the visceral mass

Contains the internal organs

Describe the mantle

A fold of tissue that drapes over the visceral mass; space between the mantle and the visceral mass is called the mantle cavity

What is responsible for secreting the shell?

The mantle is responsible for secreting the shell

List the three layers of the shell in order

Periostracum, prismatic layer, and the nacreous layer

What is another name for the nacreous layer?

Mother-of-pearl layer

What are the gills of HAM often indicated as?

One or more pairs of bipectinate gills

What is the specialized rasping (scraping) organ of a mollusc?

The radula

What organ does the radula sit upon?

The odontophore

How is food brought into the mouth of HAM?

They are brought into the mouth because they are bound to mucous secreted by the salivary glands

Is the circulator system in HAM open or closed?

HAM has an open circulatory system

Describe the metanephridia

The excretory organs of HAM

Describe the nephrostome

The funnel in HAM that leads into the exit, the nephridiophore

Describe the nephridiophore

Where waste leaves the body in HAM

Describe the trocophore larvae

The free-swimming ciliated larvae in most molluscs

Describe the veliger

The second larval stage in some molluscs (gastropods)

What is the spat stage?

A stage in some molluscs where they attach themselves to a surface

Name the three evolutionary innovations occurred among gastropods

Changes in the shell, increased development of the head (cephalization), and the embryonic process of torsion

What form of symmetry do gastropods exhibit

Asymmetry

Describe the operculum

A hardened plate on the back of the foot of a gastropod that closes the aperture when the body is withdrawn

What is the typical diet for most gastropods?

They are typically herbivores, but some are specialized to be carnivores

How do aquatic gastropods breathe?

They use gills for respiration

How do terrestrial gastropods breathe?

They obtain oxygen via a well vascularized mantle

What are some subclasses of gastropods?

Prosobranchia, opisthobranchia, pulmonata

What are some examples of Class Bivalvia?

Mussels, clams, scallops, oysters, and shipworms

Does Class Bivalvia possess cephalization?

They possess very little to no cephalization

Does Class Bivalvia possess radula?

They do not possess a radula

Is Class Bivalvia aquatic (fresh water) or marine (salt water)?

They are both (species are found in both fresh and salt water)

How does Class Bivalvia feed?

They use the cilia on their gills to filter feed

Is Class Bivalvia sessile or motile?

They are generally sessile for filter feeding

What is another term for valve?

Shell

Why are they called bivalves?

They have two valves (shells) connected by a hinge ligament

How are the two valves held together?

They are held together by a hinge ligament

How are the two valves in Class Bivalvia drawn together?

They are drawn together by adductor muscles

What is the oldest part of Class Bivalvia's shell?

The umbo is the oldest part of the shell

Describe the pedal gap

A specific part of a shell of Bivalves that allows for burrowing with the foot

Describe the siphons

Long tubular extensions of the mantle with both inhalant and exhalent openings

Certain molluscs do not possess a foot, but attach themself to a surface. How do they do this?

They fuse or cement one of their shells to the surface

How do most bivalves move?

They extend their foot out between the valves and use it to pull themselves forward

How do scallops move?

They swim by clapping their valves (shells) together to create propulsion

Are Bivalves monoecious or dioecious?

They are dioecious (male and female reproductive parts in separate individuals)

What larval forms do marine bivalves produce?

They produce free swimming trochophore and veliger larvae

What larval form do freshwater bivalve produce?

They produce larvae called glochidia

Describe glochidia

They are housed in the outer gills of fish and then parasitize the fins and fills of fish when released

What is another name for the foot?

The retractor

Describe the pallial line

The point of attachment of the mantle to the valve

What is another anme for the mantle?

The pallium

What is another name for the pair of gills in bivalves?

Ctenidia (singular: ctenidium)

Where does the food enter in a bivalve?

They enter through the incurrent siphon

Where does waste and gill-cycled water escape?

They leave through the excurrent siphon

Describe the first step of digestion in bivalves

Food enters the incurrent siphon and onto the mouth

Describe the second step of digestion in bivalves

Food goes from the mouth into the esophagus

Describe the third step of digestion in bivalves

Food goes from the esophagus into the stomach where the food is surrounded by glandular digestive glands

Describe the fourth step of digestion in bivalves

Digested particles pass through the ducts into the digestive glands, where they are absorbed

Describe the style sac

It rotates and frees enzymes for mixing with the food particles

Describe the fifth step of digestion in bivalves

More coarse particles go through the intestine (where little absorption occurs)

Describe the sixth step of digestion in bivalves

The residual waste passes through the rectum which opens into the anus and exits out the excurrent siphon

Describe the first step of the excretory system in bivalves

Water and waste from the coelom is filtered by each nephridium

Describe the second step of the excretory system in bivalves

The nephridium leads into the bladders where water and waste is retained and stored

Describe the third step of the excretory system in bivalves

After being stored in the nephridium, waste and water is released into the suprabranchial chambers

Describe the fourth step of the excretory system in bivalves

Dilute urine from the suprabranchial chambers exits out the excurrent siphon

Describe the nephridium

Waste and water are retained and salts are reabsorbed into the body. It also bends 180 degrees to dilate into the bladder.

What are the three pairs of ganglia in Bivalves

Cerebral visceral, and pedal

Describe the cerebral ganglia

They connect to the other ganglia with nerve trunks

Describe the pedal ganglia

They are connected to the cerebral ganglia. They are connected to motor nerves that supply the muscles of the foot.

Describe the visceral ganglia

They give off motor nerves to the posterior retractor and adductor muscles. They have nerve trunks connected to sensory receptors on the fringe of the mantle.

How are gastropod shells built?

They are built as a series of spirals called whorls

What parts does the circulatory system of a Bivalve include?

Auricles, ventricles, veins, and arteries

Describe the function of the auricles

A pair of chambers that receive blood

Describe the function of the ventricle

A muscular pump

Describe the function of the arteries

They distribute blood to the tissues and tissue spaces through the body

Describe the function of the veins

They return blood to the auricles after it is oxygenated in the gills

Is the circulatory system of a bivalve open or closed?

It is open because arteries and veins are not continuous with one another

Describe the first step in the circulatory system of a bivalve

Blood from the ventricle is pumped into an anterior and posterior aorta

Where does the heart reside within a bivalve?

It resides within the pericardial cavity within the visceral mass

Describe the second step in the circulatory system of a bivalve

The anterior aorta conducts blood through its branches to the anterior digestive structures, the muscular foot, and the mantle in the anterior and ventral part of the body. The posterior aorta supplies blood through its branches to the posterior visceral structures as well as the mantle

How is waste carbon dioxide discharged in bivalves?

Waste and carbon dioxide are discharged into sinuses (tissue spaces)

How is food and oxygen absorbed in bivalves?

Food and oxygen is absorbed from the sinuses (tissue spaces)

Describe the third step in the circulatory system of a bivalve

Veins recover blood from the sinuses and either go to the nephridia or the mantle and gills into the auricles. Waste is filtered through the nephridia.

Describe the fourth step in the circulatory system of a bivalve

Veins from the nephridia go to the gills and absorb oxygen in which it returns to the auricle via a vein. Some respiration also takes place in the periphery in the mantle.

What defense mechanism do sea slugs possess?

They have developed complex chemical and biological defenses to ward off their predators

Identify A in the diagram

Pericardial Cavity

Identify B in the diagram

Digestive Gland

Identify C in the diagram

Stomach

Identify D in the diagram

Mouth

Identify E in the diagram

Ventral (Anterior) Adductor Muscle

Identify F in the diagram

Labial Palp

Identify G in the diagram

Intestine

Identify H in the diagram

Gonad

Identify I in the diagram

Foot

Identify J in the diagram

Mantle

Identify K in the diagram

Periostracum (Outer Layer)

Identify L in the diagram

Auricles and Ventricle (Heart)

Identify M in the diagram

Dorsal (Posterior) Adductor Muscle

Identify N in the diagram

Anus

Identify O in the diagram

Excurrent Siphon

Identify P in the diagram

Incurrent Siphon

Identify Q in the diagram

Gills