Lecture 14

Question 1

Phylum Mollusca Characterisitcs

Answer 1

Includes:Snails, clams, mussels, octopuses, chitons, nudibranchs, squid, etc
• Lophotrochozoan Protostomes
• Triploblastic
• Coelomate (coelom is confined to small area around the heart)
• Bilateral symmetry
• Bilateral asymmetry in some
• Hydrostatic skeleton, and in some, a shell
• Complete gut
• No metamerism
• Reproduction: Sexual reproduction (monoecious or dioecious), no asexual reproduction
• Organ-system grade of organization
• Mostly open circulatory system
• Closed in cephalopods

Question 2

Classes Phylum Mollusca

Answer 2

Class Gastropoda:
• Snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies

Class Bivalvia: two valves (i.e. shells)
• Mussels, clams, scallops, oysters, and shipworms • Mostly sedentary filter feeders

Class Cephalopoda:
•Squids, octopuses, nautiluses, devilfish, and cuttlefish
• Marine active predators

Question 3

can Cephalopoda be terrestrial?

Answer 3

No! only marine, however, some gastropods are terrestrial

Question 4

Mollusca – Form and Function

Answer 4

consists of two basic parts:
• Head-foot:
feeding, cephalic, sensory, locomotor organs
• Visceral mass:
digestive, circulatory, respiratory, and reproductive organs

Many molluscs have a protective shell secreted by the mantle

Question 5

Head characteristics (mollusca)

Answer 5

• Well-developed head with mouth and sensory organs
• Mouth contains a structure unique to
molluscs; the radula
• Radula is a rasping, protrusible,
tonguelike organ found in most molluscs

Question 6

Foot Characteristics

Answer 6

• Adapted for:
• Locomotion and/or Attachment
• Usually a ventral, sole-like structure
• Modifications (e.g.)
Laterally compressed foot (bivalves)
Funnel (siphon) for jet propulsion in cephalopods

Question 7

Mantle

Answer 7

In mollusca

• Mantle is a sheath of skin, extending dorsally from the visceral mass, that wraps around each side of the body
Protects the soft parts
Outer surface of the mantel secretes the shell

Question 8

Mantle Cavity

Answer 8

In mollusca

• houses respiratory organs (gills or a lung)
• exposed surface also participates in gas exchange
• Products from digestive, excretory, and reproductive systems empty into the mantle cavity

Question 9

Reproduction in mollusca

Answer 9

• Sexual reproduction only (mostly dioecious)

* Most pass through free-swimming trochophore and veliger larval stages

Question 10

Trocophore larvae

Answer 10

Molluscs and annelids have a trochophore larvae

a free-swimming ciliated marine larva
characteristic of members of the Lophotrochozoa clade

Question 11

Veliger larvae

Answer 11

free-swimming larva of most marine snails, and bivalves. It develops from a trochophore and has the beginning of a foot, shell, and mantle

Question 12

Functions of Circulatory system

Answer 12

transports:
 • Gases
• Nutrients
• Waste
• Hormones 
• (heat)

Question 13

Why is diffusion bad for larger organisms

Answer 13

though simple, it takes a very long time so only works for small flat lil fellas

Question 14

Types of Circulatory Systems

Answer 14

Closed circulatory system

Open circulatory system

Question 15

Closed circulatory system

Answer 15

• Blood is contained within vessels

* Vertebrates and some invertebrates (e.g. annelids, cephalopods)

Question 16

Open circulatory system

Answer 16

• Blood is confined to vessels in only a
portion of circuit through body
• Blood mixes with interstitial fluids (i.e. fluids between cells) in the hemocoel
• Because it is mixed with fluid, it is properly called hemolymph
• Arthropods and some molluscs

Question 17

Class Gastropoda characteristics

Answer 17

Phylum mollusca
 Very diverse
Many, but not all, have shells
Terrestrial or aquatic
bilateral symmetry but visceral mass is asymmetrical

Question 18

Adaptations to Avoid Fouling in gastropods

Answer 18

The loss of the right gill reduces the effects of fouling

exhibit bilateral asymmetry

Question 19

class bivalvia characteristics

Answer 19

two valves (i.e. shells)
• Mussels, clams, scallops, oysters, and shipworms
•Marine and freshwater forms
• Mostly sedentary filter feeders , filter by ciliary action
•No head, no radula
•Very little cephalization

Question 20

What is Cephalization

Answer 20

concentration of sensory and neural organs

Question 21

Ocelli

Answer 21

simple eye or eyespot in many types of invertebrates AND BIVALVIA

Question 22

Bivalvia - Locomotion

Answer 22

sedentary (mussels) or sessile (oysters)
or move slowly

some move by clapping their valves together

Question 23

Class Cephalopoda charcteristics

Answer 23

• Squids, octopuses, nautiluses, devilfish, and cuttlefish
• Most complex molluscs
• Marine predators
• chiefly eat small fishes, other molluscs, crustaceans, and worms
• Highly mobile
• Vary in size
• Tentacles and arms capture prey by adhesive secretions or by suckers

Question 24

How does Class Cephalopoda move

Answer 24

Swim by expelling a jet of water from their mantle cavity through funnel (derived from the foot)

Question 25

Cephalopod - Form and Function

Answer 25

only shelled Cephalopods is Nautilus species

Cuttlefish and squid have an internal
shell called a pen

octopus have no shell