chapter 10 part 1

part 1

What does the term Phylum Mollusca describe?

“Soft-bodied” animals, many of which have shells, but not all

How far back do mollusk fossils date?

More than 500 million years.

Which mollusks have changed little from their ancestors?

Some species of mollusks, such as the chambered nautilus.

When did many species of mollusks become extinct?

About 65 million years ago

What major event caused the extinction of many mollusk species?

Earth was hit by a giant meteorite.

What is the second largest animal phylum?

Mollusks (over 100,000 species).

What type of body do mollusks have?

Soft-bodied, mostly bilateral, unsegmented invertebrates.

Where is the coelom located in mollusks?

Around the heart.

Do most mollusks have shells?

Yes, most have shel

What kind of digestive tract do mollusks have?

Complete, one-way digestive tract with a mouth and anus.

What is cephalization in mollusks?

They have a distinct head with sense organs and brain.

How do mollusks move?

Locomotion by muscular foot.

What organs do mollusks have?

Heart, liver, gills, kidney.

How are mollusks classified?

Based on shell presence, shell type, and foot type.

How many major mollusk classes are there?

Three (major) classes.

What are the three major classes Of Mollusks?

Gastropods

Bivalves

Cephalopods

What does “gastropod” mean?

“Stomach foot”.

What animals are gastropods?

Snails and slugs.

Do gastropods have shells?

Snails have one shell (univalve); slugs have no shell.

What does “bivalve” mean?

Two shells.

What does the bivalve foot look like?

“Hatchet foot”.

What animals are bivalves?

Clams, mussels, oysters, scallops.

What does “cephalopod” mean?

“Head foot”.

What animals are cephalopods?

Squid, octopus, cuttlefish, chambered nautilus.

Which cephalopod has a shell?

Chambered nautilus

How many parts are in the mollusk body plan?

Four parts.

List the four parts of mollusk body plan?

1. foot

2. Mantle

3. Shell

4. Visceral Mass

What is the function of the foot?

Used for crawling, burrowing, and tentacles.

What is the mantle?

A thin layer of tissue that covers organs.

What is the shell made of?

Made by glands in the mantle that secrete calcium carbonate.

What is the visceral mass?

Contains the guts (internal organs).

What are the different foot structure of the Mollusca?

Flat structures

Spade-shaped structure

Tentacles

What foot structure is used for crawling?

Flat structures (snail).

What foot structure is used for burrowing?

Spade-shaped structures (clam)

What foot structure is used for capturing prey?

Tentacles (squid and octopus).

A rasping, tongue-like feeding structure.

The radula

Where is the radula found?

In most mollusks except bivalves.

What is the radula made of?

Tiny rows of chitinous teeth for scraping.

What is insect (and arthropod) blood called?

Hemolymph.

What does hemolymph mean?

No separation of blood and extracellular fluid.

What oxygen transport pigment does it contain?

Hemocyanin.

What color is hemolymph when oxygenated?

Blue (due to Cu).

What is blood used for in animals?

To transport water and food throughout the body.

What carries oxygen in human blood?

Hemoglobin, which gives blood its red color.

Do insects use blood to carry oxygen?

No.

How is oxygen distributed in insects?

Through a system of tubes and air sacs.

What color is insect blood?

Colorless, pale yellow, or green.

Which one is the simpler of the two systems open or closed circulatory system?

Open circulatory system

What does the heart pump in an open circulatory system?

The heart pumps hemolymph into an open cavity called a hemocoel.

What happens to hemolymph in the hemocoel?

It mixes with interstitial fluid and bathes the internal organs.

What does hemolymph deliver?

Nutrients and, in some cases, gases such as oxygen.

How is hemolymph moved in some animals?

The heart is simply an aorta or other blood vessel, and hemolymph is pulsed throughout the body by muscle contractions.

Are there arteries or major veins in an open circulatory system?

No, there are no arteries or major veins.

What is the blood pressure like in an open circulatory system?

Blood pressure is very low.

What do organisms with an open circulatory system typically have?

A relatively high volume of hemolymph and low blood pressure.

What animals have open circulatory systems?

Insects, spiders, and most mollusks

Which mollusks have a closed circulatory system?.

Cephalopods (squid and octopus)

How many hearts do cephalopods have?

Three hearts

What structures are present in a closed circulatory system?

Blood vessels and capillaries.

What do two of the hearts do in cephalopods?

Two of the hearts control the tentacles.

What does the third heart do?

One heart pumps the blood around the body.

Do most mollusks have separate sexes?

Yes, most mollusks have separate sexes (dioecious).

Are some mollusks hermaphroditic?

Yes, some are hermaphroditic (monoecious).

What does the life cycle of many mollusks include?

A free swimming, non-shelled, ciliated larval stage

What is the larval stage of mollusks called?

A trochophore.

What occurs in sex change in the Mollusca?

It is almost exclusively protandric.

What does protandric mean?

Sex change male to female

In which mollusks has protandry only been reported?

Gastropods and bivalves.

How does a pearl begin its life?

A pearl begins its life inside an oyster’s shell when an intruder, such as a grain of sand or bit of floating food, slips in between one of the two shells of the oyster and the mantle.

How does an oyster protect itself from irritation?

The oyster begins covering the uninvited visitor with layers of nacre.

What is nacre?

The mineral substance that fashions the mollusk’s shells.

What is another name for nacre?

Mother-of-pearl.

How is a pearl formed?

Layer upon layer of nacre coat the grain of sand until an iridescent gem is formed.

Which mollusk class is the largest?

Gastropoda.

Are gastropods usually single-shelled or multi-shelled?

Usually single-shelled.

How many named gastropod species are there?

About 70,000.

Q: What animals are included in Gastropoda?

Snails and slugs.

Where do gastropods live?

Marine, freshwater, and terrestrial environments

Do slugs have shells?

Slugs lack a shell.

How many sets of tentacles do snails have?

One or two sets of tentacles on top of the head.

What type of brain do snails have?

A very small cerebral ganglion.

How many sections does the cerebral ganglion have?

Four distinct sections.

Where is the mouth of a snail located?

At the bottom of the head, near the tentacles.

How do most land snails breathe?

They have a lung, so they breathe air.

How many pieces make up a gastropod shell?

One piece — univalve.

Can gastropod shells be coiled or uncoiled?

Yes, they may be coiled or uncoiled.

What part of the shell contains the oldest and smallest whorl?

The apex.

Can shells coil to the right or left?

Yes, shells may coil to the right or left.

What controls shell coiling direction?

It is genetically controlled.

What do most gastropods eat?

Most are herbivores.

How do herbivorous gastropods feed?

By scraping off algae using the radula.

What are scavenger gastropods?

Gastropods that feed on dead organisms.

How do carnivorous gastropods feed?

They drill (using a modified radula) into other mollusks.

How many shells do bivalve mollusks have?

Two shells (valves).

What animals are bivalves?

Mussels, clams, oysters, scallops, shipworms.

How do most bivalves feed?

They are mostly sessile filter feeders.

What holds bivalve shells together?

A hinge ligament.

Do bivalves have a coelom?

Yes, bivalves have a coelom.

What type of circulatory system do bivalves have?

An open circulatory system.

How do bivalves breathe?

Through gills.