Mollusks and Echinoderms

What type of development does the phylum Mollusca have?

protostome

Which phylum has a trochophore ancestor?

Mollusca

What is the second largest invertebrate phylum?

Mollusca

Which phylum, between Mollusca and Echinodermata, is more diverse?

Mollusca

What is the Latin word for the phylum Mollusca and what does it mean?

“molluscus”; soft

What phylum is associated with Annelids and why?

Mollusca; they share a common larval form: trochophore larvae

What kind of body cavity does the phylum Mollusca have?

true coelom

How many distinct parts does a mollusk’s body have?

3

What are the distinct parts of a mollusk’s body?

foot, head, and visceral mass (covered by mantle)

What type of symmetry does a mollusk have?

bilateral symmetry

What feature do most mollusks have?

shells (internal and external)

What is a mollusk’s foot?

muscular organ used for locomotion

What does a mollusk’s head contain?

the mouth, sense organs, and ganglia

What does a mollusk’s visceral mass contain?

the heart and organs of digestion, excretion, and reproduction

What are the 2 functions of a mollusk’s mantle?

covers the visceral mass, secretes the shell

How is a shell an adaptation for mollusks?

it provides protection for their soft bodies

What is the problem with a shell for mollusks?

inhibits gas exchange

What are a mollusk’s gills?

organs specialized for gas exchange with water that pass food to mouth

What is a mollusk’s mantle cavity?

space where gills are found

What types of feeders are mollusks?

herbivores, carnivores, and filter feeders

What is a radula and which phylum has it?

flexible tongue-shaped structure used by some to obtain food

How do mollusks that are filter feeders feed?

Water enters through a siphon and flows over the gills; cilia move the food to the mouth

What organelle do aquatic mollusks use for respiration?

gills

What mollusks use a mantle for respiration?

land snails and slugs

What do land snails and slugs use for respiration?

mantle

Open system of circulation in mollusks:

blood is pumped by a simple heart through vessels; it then leaves the vessels into sinuses, then to the gills and back to the heart

Which mollusks have an open circulatory system?

snails, clams, oysters

What is the body cavity called in organisms with open circulatory systems?

hemocoel

What does a closed circulatory system mean?

blood is completely contained in vessels

What are examples of mollusks with closed circulatory systems?

octopus and squid

How do mollusks excrete waste?

by nephridia

How do mollusks reproduce?

some are hermaphroditic, some have external fertilization, some have internal fertilization

What are the 3 classes of mollusca?

Gastropoda, Pelecypoda, and Cephalopoda

What does ‘Gastropoda’ mean?

stomach foot

Examples of members of Gastropoda: (5)

snails, slugs, abalones, nudibranches, oyster drill

How many shells do members of Gastropoda have?

univalves or no shell

Members of Gastropoda undergo ______. What is this?

torsion; twisting of the visceral mass during development enabling the mantle cavity to be in the front allowing for space to retract head into the shell

In Gastropods, mucus is secreted by _______ and has 2 functions:

glands; helps it move and allows for gases to be exchanged

What is the class Pelecypoda also called?

Bivalvia

Examples of members of Pelecypoda: (4)

oyster, clams, scallops, mussels

How many shells do members of Pelecypoda have?

bivalves

What opens and closes the 2 shells of a bivalve?

adductor muscle

How many layers do the shells of a bivalve have and function?

3; prismatic (outer layer for protection)

, middle layer (for strength, made of CaCO3), and inner layer (protects the body)

Locomotion of Pelecypoda:

sessile

Feeding of Pelecypoda:

filter-feeders

What are the gills of Pelecypoda used for?

feeding and respiration

Do Pelecypoda have a foot?

yes; a muscular foot that helps dig into sand

Do members of Pelecypoda have cephalization?

no

Which class of mollusks form pearls?

Pelecypoda

What does “cephalopoda“ mean?

head foot

Examples of members of Cephalopoda:

squid, octopus, cuttlefish, nautilus

How many shells do members of Cephalopoda have?

external, internal, or no shell

Do members of Cephalopoda have a foot?

no; foot has developed into tentacles which can have suction cut or hooks

What abilities do tentacles of Cephalopods have?

chemosensory

What type of feeders are Cephalopods?

carnivores

What type of habitats do Cephalopods live in?

marine

How do Cephalopods move?

by jet propulsion by expulsion of water from the mantle cavity

Do Cephalopods have cephalization?

yes; highy developed

Do Cephalopids have a brain?

yes; well developed

What mental capabilities do Cephalopods have?

ability to learn and remember

What ability do the eyes of Cephalopods have?

well developed with lens to focus

What does the word “echinodermata“ mean?

hedgehog-skinned

What type of development does the phylum Echinodermata have?

deuterostome

What type of symmetry do echinoderms have?

radial symmetry

What type of feeders are echinoderms?

carnivores

What types of environments do echinoderms live in?

marine

What type of body plan do echinoderms have?

5-part, pentaradial

What unique system do echinoderms have?

water vascular system

All echinoderms have ________. These are well developed in some like ___________ but reduced in others like ___________.

spines; sea urchins; sea cucumbers

What type of skeleton do echinoderms have?

endoskeleton (internal skeleton)

What is an echinoderm’s skeleton composed of?

plates of calcium carbonate found beneath the skin

Describe the nervous system of echinoderms:

central nervous system with sensory areas; no true brain; nerve ring and radial nerves

What type of symmetry is echinoderm larvae?

bilateral; changes its symmetry to adult

What type of larvae do echinoderms have?

bipinnaria

What are the 3 functions of echinoderms’ water vascular system?

locomotion, respiration, and food capture

Describe the process of the water vascular system:

1. water enters the system through the madreporite (sieve plate)

2. water passes through the stone canal to the ring canal

3. ring canal then passes water down each arm’s radial canal

4. each radial canal sends water to the ampullae which connect to the tube feet

5. water inflates the ampullae, causing it to create suction in the bottom of the tube feet

How many digestive glands are in each arm of echinoderms, and what do they connect to and how?

2; stomach; pyloric ducts

How many regions does an echinoderm’s stomach have and what are they?

2; pyloric stomach and cardiac stomach

How do echinoderms feed?

the cardiac stomach is everted through the mouth; digestive enzymes are released; partially digested food is taken in and passed to l=pyloric region and then to anus

What do echinoderms eat?

bivalves

How do echinoderms coordinate their movement?

a nerve ring sends radial nerves down each arm

What are located on the end of sea stars’ arms and what do they detect?

sensory cells; light and chemicals

What do some brittle stars have for sensory abilities and what do these things do?

lens cells that focus light on receptor cells

What special ability do echinoderms have and what does it require?

regeneration; if part of the central ring canal is intact

Describe the circulatory system of echinoderms:

no circulatory system; use WVS

What are the 2 ways echinoderms respirate?

through tube feet; can also occur through skin gills that project through the epidermis

How do echinoderms reproduce?

separate sexes, external fertilization (egg and sperm discharged into water)

Are males and females distinguishable in echinoderms?

no

What are the 5 classes of echinoderms?

Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea

What class of echinoderms is the most ancient?

Crinoidea

What class of echinoderms includes sea lilies and feather stars?

Crinoidea

What animals does Crinoidea include?

sea lilies and feather stars

What type of feeders are Crinoidea?

filter feeders

What type of locomotion does Crinoidea have?

sessile

What organisms does Asteroidea include?

sea stars

What class of echinoderms are sea stars in?

Asteroidea

What organisms are in class Ophiuroidea?

brittle stars and basket stars

What class of echinoderms are brittle stars and basket stars in?

Ophiuroidea

What organisms are in class Echinoidea?

sea urchins, sand dollars, and sea biscuits