13. Mollusks

Question 0

How large is the animal group of mollusk?

Answer 0

Second largest after arthropods

Question 1

Mollusks are part of which subgroup?

Answer 1

Lophotrochozoa (protosomes)

Question 2

Mollusks - diversity?

Answer 2

Highly diverse in response to environment

• Terrestrial or aquatic
• Different morphology, mode of nutrition, reproduction

Question 3

Mollusca - body shapes?

Answer 3

Bilaterally symmetrical, triploblastic, coelomate protostomes

Question 4

Mollusca are ….. larvae

Answer 4

Trochophore larvae (marine mollusks)

Question 5

Major groups of mollusca?

Answer 5

Polyplacophora
Gastropoda
Bivalvia
Cephalopoda

Question 6

Mollusk body plan?

Answer 6

• Foot at bottom
• Mantle
• Visceral mass
  Contains gills (if aquatic) or acts as lung (if terrestrial)

Question 7

Polyplacophora means….

Answer 7

Many plates

Question 8

Characteristics of polyplacophora?

Answer 8

Segmented shell (8 overlapping plates)
Multiple gills

Question 9

Polyplacophora - feeding?

Answer 9

Omnivorous - radula scrapes algae & bryozoans

Question 10

Characteristics of bivalvia?

Answer 10

• Reduction of head
• Hinged shell
• Enlargement of foot
• Mantle cavity modified by siphons
• Enlargement of gill
• Relatively sessile
• Filter feeders
• Broadcast spawners

Question 11

Siphons?

Answer 11

Extensions of posterior mantle

Water flows in mantle cavity and then across gills that act as filters for food

Question 12

Bivalvia close shell…

Answer 12

With their large adductor muscles

Question 13

Mantle of bivalvia is lined with…

Answer 13

Eyes - to detect motion and light

Question 14

How large is the gastropoda group?

Answer 14

Most diverse group of mollusks

Question 15

Gastropoda - habitat?

Answer 15

Terrestrial or aquatic

Question 16

Gastropoda - feeding?

Answer 16

Herbivores, predators, scavengers

Question 17

Gastropoda - reproduction?

Answer 17

• Internal or external fertilization

- Either dioecious or hermaphroditic, but can produce only sperm or eggs at one time

Question 18

Some cool stuff gastropods do with their body?

Answer 18

• Torsion (twisting of body - 180 degrees rotation of visceral mass, mantle cavity, anus moved over head)
• Coiling of visceral mass

Question 19

Characteristic of land snails?

Answer 19

Eyes on tips of tentacles

Question 20

Characteristic of cone snail?

Answer 20

Radula modified into toxic harpoon (peptide toxins)

Question 21

Some gastropods have nudibranchs which allows….

Answer 21

Secondary de-torsion

Question 22

Some gastropods prey on tentacles of ……

Answer 22

Cnidarian polyps and re-used the cnidocytes

Question 23

Body characteristics of cephalopoda?

Answer 23

• Subdivided foot (arms, tentacles)

- Enlarged head, reduced shell)

Question 24

Cephalopods - feeding?

Answer 24

Predators

Question 25

As predators, cephalopods have…

Answer 25

• Excellent vision
• Complex behaviour (visual communication with colour and texture, cryptic colouration)
• Ink sac for defense
• Closed circulatory system
• Mantle & siphon used for jet propulsion
• Arms with suckers &/or hooks - some have 2 elongated tentacles

Question 26

Cephalopod reproduction?

Answer 26

Separate sexes!! (with elaborate courtship)

• Internal fertilization (males transfer sperm via specialized arm - hectocotylus)
• Females die after laying eggs (or after eggs hatch)
• NO TROCHOPHORE LARVA

Question 27

Nautilus - example of a cephalopod. Characteristics?

Answer 27

• 80-90 arms
• Regulate buoyancy with gases in chambered shell
• Only extant shelled cephalopod

Question 28

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Answer 28

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