Lab 5 Mollusca - EVERYTHING
What features contribute to the success of squid as predators?
- well-developed eyes - extensible tentacles with suckers - siphons for jet propulsion - fins for maneuverability - closed circulatory system for efficient gas transfer - aerodynamic, fusiform body shape
REPRODUCTION:Describe the types of reproduction that occur in the group (e.g. sexual vs. asexual) and any other characteristics or specializations they may have for reproducing (e.g. monoecious vs. dioecious, fission, budding, etc.). A)Sexual B)Monoecious ONLY C)Dioecious ONLY D) Both monoecious and dioecious E) Some alternation of sexual and asexual stage F)Asexual reproduction G)External fertilization mostly H) Internal fertilization mostly I) Both internal and external fertilization
A)Sexual D) Both monoecious and dioecious I) Both internal and external fertilization
ORGANIZATION:At what level is the basic body plan organized? (e.g. cell, tissue, organ, etc.) A)Tissue level B)Organ level C)none of the above
B)Organ level
Do organisms in Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Octopodiformes have a shell?
no
Is torsion and coiling the same thing?
no
The great diversity of molluscs is an example of what evolutionary phenomenon?
adaptive radiation
Class Cepalopoda Modified Shell Nautilus
gas-filled chambers
What is the arrow point to?
vascularized mantle Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Pulmonata
12. Which are 2 disadvantages of an open circulatory system? a) cannot increase or decrease blood flow volume b) does not support high metabolic rates and active lifestyles c) allows greater control over body temperature
Both a & b { a) cannot increase or decrease blood flow volume & b) does not support high metabolic rates and active lifestyles} --> Advantages: allows greater control over body tempreture and renders animal much less vulnerable to body compression due to high pressures(permitting molluscs to thrive at greater depths and other animals like insects to survive in higher ambient temperatures).
Class Polyplacophora Characteristics
Chitons Live in the intertidal zone on rocks Grazers Eight separate shell plates or valves Allows flexing upward and curling into a ball Pallial groove on ventral surface Marks separation between foot and mantle
Class Gastropoda Subclass Prosobranchia Characteristics
Shelled aquatic snails - Mostly marine Mantle modified to form siphon - Brings in water to ctenidia Have operculum - Hard covering over aperture
What structure in the image indicates the specimen's sex?
nidamental glands
Phylum Mollusca Class Bivalvia Name Meaning
bi = two valva = leaf of a door
What type of symmetry do molluscs have?
bilateral symmetry
Class Polyplacophora
chiton
What is the common name for Polyplacophora?
chitons
mantle
epidermal layer that covers all of visceral mass, delimis the mantle cavity; mantle also secretes shell, in those species that have one
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Euthyneura Name Meaning
euthy- straight -neura - nerve
Digestion/Feeding Class Bivalvia
filter feeder
Do organisms in Phylum Mollusca Class Cephalopoda have an open or closed circulatory system?
closed
Class Gastropoda Name Meaning
gaster- = stomach -pous = foot "stomach foot"
Class Ployplacophora Name Meaning
poly- = many plax = plate -phoros = bearing "many plate-bearing"
Digestion/Feeding Class Cephalopoda
predator
What does Class Bivalvia not have?
radula
Class Cepalopoda Modified Shell Cuttlefish
reduce to an internal "cuttlefish bone"
Class Cepalopoda Modified Shell Squid
reduce to an internal "pen"
What type of shell does Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes have?
reduced shell
Phylum Mollusca Class Scaphopoda Name Meaning
skaphe = boat pous = foot
What does the Class Cephalopoda use for locomotion?
jet propulsion
Phylum Mollusca Class Cephalopoda Name Meaning
kephale- head pous- foot
Gastropoda: Coiling of Shell Conispiral (Sinistral)
left-handed coiling
What is the common name for Gastropoda?
snails, slugs
How does excretion work in molluscs?
metanephridia (excretory gland)
Digestion/Feeding Class Gastropoda
mixed
Why not have a single type of shell in Gastropod?
Environmental adaptations Predation adaptations - Predators prefer dextral over sinistral)
Describe the evolutionary phenomenon that led to the great diversity of molluscs in a short sentence.
Evolution of ecologically diverse taxa from a common ancestor after moving into a new environment
Do nudibranch have internal or external gills?
External gills In some heterobranchs (nudibranchs), the gills are outside of their body (hence the name; "nudi" =naked, "branchs"= gills)
Identify the structure indicated by line B
Gills
What is the function of the structure indicated by line D?
Locomotion - to keep chiton attached to rocks Foot
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Octopodiformes Characteristics
Octopuses and vampire squid Poor fossil record Found in all marine habitats Associated with ocean floor No shell
What is the phylum, class, and subclass for these organisms?
Phylum: Mollusca Class: Gastropoda Subclass: Prosobranchia
What is the phylum, class, and common name for this organism?
Phylum: Mollusca Class: Polyplacophora Common name: Chiton
Adaptive radiation
the evolution of ecologically diverse taxa from a common ancestor after moving into a new environment
What are the 4 body regions characteristic of molluscs? (in order from outer to inner regions)
1. Head 2. Foot 3. Visceral mass 4. Mantle
What are two types of coiling in a shell of Class Gastropoda?
1. Planispiral 2. Conispiral
What are two types of Conispiral coiling of a shell of Class Gastropoda?
1. Sinistral 2. Dextral
What are the four body regions of Phylum Mollusca?
1. head 2. foot 3. visceral mass 4. mantle
On the figure above, match the following structure with the corresponding letter branchial heart
A
Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Characteristics
Ammonites All extinct Name comes from the Egyptian god Ammon (Amun) With shells - Like Nautilus' With distinctive sutures that marked where the septa joined the shell wall
Eucoelomate
An organism that has a complete body cavity where the ectoderm and the endoderm is lined by mesoderm
On the figure above, match the following structure with the corresponding letter Cecum
B
DIGESTION/FEEDING:Describe the digestive process (e.g. incomplete and extracellular) and any specializations for feeding (e.g. cnidocytes, tentacles, etc.). A) Incomplete gut B)Complete gut (mount and anus) C)Intracellular digestion only D)Extracellular digestion only E)Extra and intracellular digestion F)Labial palps
B)Complete gut (mount and anus) D)Extracellular digestion only F)Labial palps Labial palms are in bivalves like clams.
CIRCULATION:Describe the circulatory system (e.g. diffusion, open system, etc.). A)Diffusion B)Open circulatory system C)Closed circulatory system D)3-chamber heart E)4-Chamber heart F)No circulation at all
B)Open circulatory system C)Closed circulatory system D)3-chamber heart 3-chamber heart is only in some molluscs. Most have a single ventricle and a single auricle/atrium.
What is the arrow pointing to?
Bivalve umbo
11. Why are sensory structures more prevalent on cephalopods than on bivalves? a) Cephalopods are active predators and need acute vision to spot prey b) Bivalves will NEVER need eyes cause they all filter feed c) Most bivalves are sessile and will not need the use of complex sensory structures
Both a & c -->Because cephalopods are highly active predators , they have benefited from any advances in their sensory systems, particularly in the area of vision. Over thousands of generations they have evolved acute vision to assist them in spotting and capturing prey.
How does sensation work in Class Cephalopoda?
Brain and eyes
On the figure above, match the following structure with the corresponding letter gill
C
SKELETON/SUPPORT:List the structures or ways this group of animals support themselves (e.g. hydrostatic skeleton, exoskeleton, etc.). A)Hydrostatic skeleton B)Endoskeleton C)Exoskeleton
C)Exoskeleton
MOVEMENT/LOCOMOTION:What structures are used to help them move around their environment?(e.g. types of muscles, jointed legs, cilia, etc.). A)Cilia B)Moves using flagella C)Jet propulsion D)Pedal disk E)Hydrostatic skeleton F)Muscular foot via pedal waives of muscle contraction
C)Jet propulsion E)Hydrostatic skeleton F)Muscular foot via pedal waves of muscle contraction
EXCRETORY/OSMOREGULATION:List how the group eliminates waste from their systems (e.g. diffusion, nephridia, Renette cells, Malpighian tubules etc.). A)Diffusion B)Protonephridia = Flame cell C)Metanephridia D)Urea E)Malpighian tubules F)Kidneys
C)Metanephridia
What type of support to molluscs have?
CaCO2 shell secreted by mantle
Phylum Mollusca Class Cephalopoda Circulation
Cephalopods unlike other molluscs have a closed circulatory system - With hemocoel, which is a blood-filled body cavity
Phylum Mollusca Class Bivalvia Characteristics
Clams, oysters, scallops and mussels Rely on flow of water for food and waste excretion No radula Most are suspension feeders, some are deposit feeders Gills in this group have multiple functions: feeding, respiration and respiration Many have poorly developed senses Notable exception are scallops that have complex eyes
Identify the class of specimen depicted.
Class Bivalvia
What class has a modified foot?
Class Cephalopoda muscular foot is modified into tentacles
Gastropoda: Coiling of Shell Planispiral
Coiling occurs in a single plane Thought to be ancestral
Identify the class of the specimen depicted
Class Polyplacophora
Gastropoda: Coiling of Shell Conispiral
Coiling creates a spiral in 3 dimensions
Digestion/Feeding of Molluscs
Complete gut Radula Rasping mouthpart used for cutting or scaping Chitinous ribbon with minute teeth Present in almost all molluscs except bivalves
SYMMETRY:What type of symmetry is found in the basic body plan? (e.g. asymmetrical, radial. etc.) A)Asymmetry B)Radial symmetry C)Pentaradial symmetry D)Bilateral symmetry
D)Bilateral symmetry
RESPIRATION:Describe how the group respires (e.g. diffusion, book lungs, gills, etc.). A)Diffusion B)Book lungs C)Lungs D)Gills inside mantle E)Gils outside the mantle F)Vascularized tissue lining the mantle cavity that acts as a lung
D)Gills inside mantle E)Gils outside the mantle F)Vascularized tissue lining the mantle cavity that acts as a lung
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes Name Meaning
Decapoda - ten feet iformes - shaped
Is this specimen male or a female?
Female because of the presence of nidamental glands.
operculum
Hard covering over aperture
What is this showing?
Hole in shells made by a radula of a predatory gastropod
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Characteristics
Includes gastropods with a gill origin different from that of other gastropods Marine, freshwater and terrestrial snails and slugs Very reduced shell or shell
What does HAM stand for?
Hypothetical Ancestral Mollusc
Respiration of Molluscs
Land snail and slug with vascularized mantle that acts like a lung - hence the name "pulmonates" (with lungs) Gills In some heterobranchs (nudibranchs), the gills are outside of their body (hence the name; "nudi" =naked, "branchs"= gills)
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Pulmonata Characteristics
Land snails and slugs Lost ctenidia Have vascularized mantle to act as lungs No operculum
Infaunal
Live within the sediment rather than on top (epifaunal) with mouths downward
What differentiates a female and male squid internally?
Male: testis Female: nidamental gland
What differentiates a female and male squid externally?
Males have hectocotyli for spermatophore transfer into female's mantle cavity
What phylum is an excellent example of adaptive radiation?
Molluscs evolved over 500 million years ago, and then evolved to fill many unoccupied niches and take over many occupied niches from existing marine animals. Selective pressures caused the divergence of different molluscs to produce the many different classes and body forms we recognize today. - Bivalves became sessile filter feeders, chitons and snails are primarily grazers and cephalopods are active predators.
What is this a picture of?
Nautilis shell
What does nudibranch mean?
Naked gill
Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Common Name
Nautiluses
Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Characteristics
Nautiluses Found in the tropical Indo-pacific Extensive fossil record Scavengers and predators of small animals in coral reefs Nautilus only living cephalopod with external shell - With internal chambers that help them stay buoyant
Do bivalves have a radula?
No, they are filter feeders
Match the following organisms' characteristics with the corresponding class or order: reduced to an internal "cuttlefish bone"
Order Decapodiformes
Match the following organisms' characteristics with the corresponding class or order: reduced to an internal "pen"
Order Decapodiformes
Match the following organisms' characteristics with the corresponding class or order: absent (no shell at all)
Order Octopodiformes
Phylum Mollusca Characteristics
Organ level organization Triploblastic Protostomes Eucoelomates Have a true coelom Bilateral symmetry Complete gut Support: CaCO2 Shell secreted by mantle Excretion via metanephridia Circulation open circulatory system Exception: cephalopods with closed circulatory system Locomotion: Muscular foot Cephalopods: foot modified into tentacles, instead use jet propulsion Sensory: complex sense organs Brain and eyes in cephalopods Most are dioecious Separate male and female Many heterobranchs are simultaneous hermaphrodites
What is the phylum, class, and common name for these organisms?
Phylum Mollusca Class Scaphopoda Common Name: tooth or tusk shells
HAM applies to which phylum and classes of organisms?
Phylum Mollusca - Class Polyplacophora (chitons) - Class Bivalvia (clams, mussels) - Class Aplacophora - Class Cephalopoda (octopus, squid, cuttlefish, nautilus) - Class Monoplacophora - Class Gastropoda (snails, slugs) - Class Scaphopoda (tush, tooth shells)
What is the phylum, class, and common name for these organisms?
Phylum Mollusca Class Bivalvia Common Name: Clams, oysters, scallops and mussels
What is the phylum, class, and common name for these organisms?
Phylum Mollusca Class Cephalopoda Common name: Squid, octopods, and nautilus and ammonites
What is the phylum, class, subclass, and common name for these organisms?
Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Common name: ammonites
What is the phylum, class, subclass, and common name for these organisms?
Phylum Mollusca Class Cephalopoda Subclass Nautiloidea Common Name: Nautiluses
What is the phylum, class, order, and common name for these organisms?
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Octopodiformes Common Name: octopus and vampire squid
What is the phylum, class, subclass, infraclass, and common name for these organisms?
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Pulmonata Common name: land snails and slugs
What is this a picture of?
Phylum Mollusca Class Cephalopoda
What is the phylum, class, order, and common name for these organisms?
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes Common Name: squid and cuttlefish
What is this showing?
Radula
What is the function of the structure indicated by line E?
Reproduction Testis
Identify the class of the specimen depicted below.
Scaphopoda
Class Gastropoda Characteristics
Snails, slugs Aquatic and terrestrial Class diversity second only to Insecta Defining feature is torsion Body rotates 180⁰ in development Anus is above mouth Unrelated to shell coiling Secondarily lost in Infraclass Heterobranchia
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes Characteristics
Squid and cuttlefish Eight arms + 2 additional tentacles Active swimmers Food source of birds, marine mammals, and humans Reduced shell Cuttlefish = cuttlebone Squid = pen
Phylum Mollusca Class Cephalopoda Characteristics
Squid, octopods, and nautilus and ammonites Reduced shell (1 genus with shell) Various defense mechanisms due to lack of shell - Jet propulsion in squid and cuttlefish -Chromatophores for camouflage or warning signs - Ink sacks discharged through anus Closed circulatory system Well developed senses and nervous system Octopods are regarded as the most intelligent invertebrates
Match the following organisms' characteristics with the corresponding class or order: gas-filled chambers
Subclass Ammonoidea Subclass Nautiloidea
What subclasses belong to the Class Gastropoda that we have to know?
Subclass Prosobranchia Subclass Heterobranchia
Describe the evolutionary phenomenon that led to the cephalopod eye and the vertebrae eye in a short sentence.
The independent development of resemblance between species as a result of similar selection pressures typically generated by comparable ecological roles.
What is the function of the structure indicated by line A?
The mantle produces the shell
Phylum Mollusca Class Scaphopoda Characteristics
Tooth or tusk shells Deposit feeder Only group to be exclusively infaunal - Live within the sediment rather than on top (epifaunal) with mouths downward Typically live offshore rather than near beaches
What type of embryonic development occurs in molluscs?
Triploblastic Protosomes Eucoelomates
Defense mechanisms belonging to Phylum Mollusca Class Cephalopoda
Various defense mechanisms due to lack of shell - Jet propulsion in squid and cuttlefish -Chromatophores for camouflage or warning signs - Ink sacks discharged through anus
6. What is an explanation for the shared feature in the previous question (#5)? a) Methods of feeding b) Method of locomotion c) Need to detect prey d) Lack of a shell
a) Methods of feeding
visceral mass
all the innards (gut, gonads, etc.)
Phylum Mollusca Class Cephalopoda Subclass Ammonoidea Common Name
ammonites
Which letter indicates the oldest part of the shell?
apex
2. What feature is shared by Gastropoda and Polyplacophora? a) number of shells b) large muscular foot c) tentacles d) torsion
b) large muscular foot
hemocoel
blood-filled body cavity
15. Among the three major groups of molluscs (Gastropoda, Bivalvia, and Cephalopoda) only the Gastropods have invaded terrestrial environments. Given their great success in marine and freshwater why have Cephalopoda not been successful on land? a) They do not have mutualistic algae on land b) Filter-feeding is not possible in the air c) They cannot move quickly on land to catch prey d) There aren't enough rocks for them to attach themselves
c) They cannot move quickly on land to catch prey
Do molluscs have a complete or incomplete gut?
complete
How does sensation work in molluscs? What class is an exception?
complex sense organs Class Cephalopoda
The cephalopod eye and the vertebrate eye demonstrate what evolutionary phenomenon?
convergent evolution
What type of reduced shell do cuttlefish have?
cuttlebone
What is this a picture of?
cuttlefish bone
Are molluscs monoecious or dioecious?
dioecious Separate male and female Many Subclass Heterobranchia are simultaneous hermaphrodites.
Digestion/Feeding Class Polyplacophora
herbivore
Class Gastropoda Subclass Heterobranchia Name Meaning
hetero- = different -branchia = gills
foot
muscular (usually for locomotion)
What do molluscs use for locomotion?
muscular foot
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Octopodiformes Name Meaning
octopus = eight feet iformes = shaped
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Octopodiformes
octopus and vampire squid
What type of circulatory system do molluscs have? Which class is an exception?
open circulatory system Class Cephalopoda is the exception with a CLOSED circulatory system
What are the arrows pointing to?
operculum Phylum: Mollusca Class: Gastropoda Subclass: Prosobranchia
What type of organization do molluscs have?
organ level
What type of reduce shell do squids have?
pen
Class Gastropoda Subclass Prosobranchia Name Meaning
proso- = forwards -branchia = gills
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Pulmonata Name Meaning
pulmoneum = lungs
9. Name the 3 functions of the gills of a mussel, which are an excellent example of a multifunctional organ.
reproduction, respiration and filter feeding. -->The gills help with feeding by collect minute food particles, act as a respiratory surface, and (in females) aid in reproduction by being used to brood eggs.
Gastropoda: Coiling of Shell Dextral (Sinistral)
right-handed coiling Most snails are dextral
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes
squid and cuttlefish
What is the arrow pointing to?
squid pen
SENSORY/NERVOUS:Describe the nervous system (i.e. ganglia, CNS, ventral nerve cord, etc.) and any sensory specializations found in the group (e.g. auricles, eyes, antennae, etc.). A)Nerve net connecting nerve cells and neurons B)Ocelli C)Cerebral ganglia D)Ventral nerve cord E)Dorsal nerve cord F)Cephalization G)Auricles H) Giant fibers
B)Ocelli C)Cerebral ganglia D)Ventral nerve cord F)Cephalization H) Giant fibers Ganglia forms a true brain in cephalopods. In other molluscs, the ganglia are paired and connected by nerve fibers.
CLASSIFICATION: Only answer the phyla, classes, subclasses and other classification that you are responsible for knowing this week in lab. *HINT: check the worksheet. A)Phylum Annelida B)Phylum Mollusca C)Phylum Nematoda D)Class Monoplacophora E)Class Pulmonata F)Class Polyplacophora G)Order Cephalopoda H)Class Scaphopoda
B)Phylum Mollusca F)Class Polyplacophora H)Class Scaphopoda
EMBRYONIC DEVELOPMENT:List the characteristics found during the formation of the blastula (e.g. triploblastic, deuterostome, etc.). A) Diploblast B)Triploblast C)Protostome D)Deuterostome E)Acoelomate F)Pseudocoelomate G)Eucoelomate (or coelomate) H)No embryonic development
B)Triploblast C)Protostome G)Eucoelomate (or coelomate)
What infraclasses belong to the Class Gastropoda that we have to know?
Infraclass Euthyneura Infraclass Pulmonata
Phylum Mollusca Class Gastropoda Subclass Heterobranchia Infraclass Euthyneura Characteristics
Marine, freshwater slugs Very reduced shell or no shell Secondarily lost torsion
Which organism of Phylum Mollusca Class Cephalopoda are the most intelligent invertebrates?
Octopods
What is the phylum, class, and common name for these organisms?
Phylum: Mollusca Class: Gastropoda Common Name: snails, slugs
What is the phylum, class, subclass, and infraclass for these organisms?
Phylum: Mollusca Class: Gastropoda Subclass: Heterobranchia Infraclass: Euthyneura
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Order Decapodiformes Common Name
Squid and cuttlefish
5. What feature do Scaphopoda and Bivalvia share? a) Reduced or absent head b) Number of shells c) Absence of a mantle d) A complex eye similar to vertebrates
a) Reduced or absent head
7. A bivalve is ecologically most similar to which of the following? a) Sponge b) Box Jelly c) Tapeworm d) Earthworm e) Octopus
a) Sponge
Class Cepalopoda Modified Shell Octopus
absent (no shell at all)
13. Which of the following do you think is a good comparison of Cephalopods to vertebrates. a) Ecologically and behaviorally similar, similar in morphology b) Ecologically and behaviorally similar, different in morphology c) Ecologically and behaviorally different, similar in morphology d) Ecologically and behaviorally different, different in morphology
b) Ecologically and behaviorally similar, different in morphology
14. Among the three major groups of molluscs (Gastropoda, Bivalvia, and Cephalopoda) only the Gastropods have invaded terrestrial environments. Given their great success in marine and freshwater why have Bivalvia not been successful on land? a) Their shell makes it impossible to live out of water. b) Filter-feeding is not possible in the air c) Locomotion on land is not practical for their body shape d) There aren't enough rocks for them to attach themselves
b) Filter-feeding is not possible in the air
8. Why do you suppose the adductor muscles are so well developed in bivalves? a) allows bivalves to open and close shells at will so they can move freely b) allows bivalves to keep their shells closed tightly as a defense mechanism agains predators c) allows bivalves to keep their shells closed tightly for better filter feeding
b) allows bivalves to keep their shells closed tightly as a defense mechanism agains predators -->To give bivalves a defensive advantage against predators by allowing them to keep their shells closed tightly
siphon
brings in water to ctenidia a soft fleshy tube-like structure equipped with chemoreceptors which "smell" or "taste" the water, in order to hunt for food. Marine gastropods that have a siphon are either predators or scavengers
3. What factor is responsible for the similarity of the feature in the previous question (# 2)? a) Presence of a shell b) Being an active predator c) Method of locomotion d) Filter feeding
c) Method of locomotion
16. Which phylum that we have covered so far in this course shares with Mollusca the characteristics of being triploblastic and unsegmented? a) Porifera b) Cnidaria c) Platyhelminthes d) Annelida e) Ctenophora
c) Platyhelminthes
Chitons appear segmented because of the 8 'valves' (shells). However, internally, chitons, show no signs of segmentation and segmentation is not known in other mollusks. What is the most likely explanation for these observations? a) Ancestral Chitons were segmented b) Ancestral mollusks were segmented c) The eight shell 'segmentation' evolved independently in chitons d) Chitons independently evolved internal and external segmentation and almost completely lost it.
c) The eight shell 'segmentation' evolved independently in chitons
4. The term 'slug' is used to refer to gastropods that have lost their shell. Evolutionary loss of a shell has occurred more than once in marine and terrestrial gastropods. Which feature would you expect to be shared by different groups of slugs? a) ability to swim b) a predatory way of life c) complex eyes similar to vertebrates d) loss of torsion
c) complex eyes similar to vertebrates --> secondarily loss of torsion & reduction of shell or complete loss of shell
10. What are the functional differences between the gills of squid and the gills of clams? a) gills of squid function in needed and reproduction b) gills of quid function in feeding c) gills of squid function only in respiration d) there are not differences, both types of gills function ONLY for respiration, they are gills!
c) gills of squid function only in respiration
Digestion/Feeding Class Scaphopoda
deposit feeder
ctenidia
specialized gills in mollusca
Torsion in Gastropods
the rotation of the visceral mass, mantle, and shell 180˚ with respect to the head and foot of the gastropod. This brings the mantle cavity and anus to an anterior position above the head.