Mollusca: Polyplacophora

Question 1

body wall and support

Answer 1

Body wall: three layers of cuticle, epidermis, and muscle; 8 calcareous
plates.

Support: 8 dorsal plates act as a protective exoskeleton; girdle surrounds
plates for support.

Question 1

synapomorphies (3)

Answer 1

Schwabe organ-sensory organ found on the ventral
surface,

8 overlapping shell plates,

poorly differentiated head without eyes or tentacles

Question 2

locomotion and body cavity

Answer 2

Locomotion: uses muscular foot to creep; can adhere using suction.

Body cavity: reduced coelom; hemocoel

Question 3

feeding/digestion and circulation

Answer 3

Feeding: herbivorous grazers, use radula to scrape algae; some species can
be omnivorous

Digestion: digestive system is a simple stomach with an elongated
intestine

Circulation: open circulatory system with a dorsal heart; ctenidia oxygenates blood

Question 4

Excretion and gas exchange

Answer 4

Excretion: nephridia filters waste from coelom and excretes it into the
mantle cavity

Gas exchange: water flows over ctenidia to facilitate oxygen uptake and
CO2 removal

Question 5

nervous system

Answer 5

Nervous system: ladder-like nervous system; nerve ring around
esophagus; chemosensory receptors on girdle; some have aesthetes
(light-sensitive organs)

Question 6

reproduction and development

Answer 6

Reproduction: sexually, with some being hermaphrodite; external fertilization, with gametes released into the water

Development: Indirect development with a trochophore larvae, which
settles and metamorphoses into an adult

Question 7

habitat (4)

Answer 7

Cold waters to tropics;

lives on hard surfaces, frock under rocks
to intertidal zones;

few species live in deep waters;

exclusively marine

Question 8

fun facts (2)

Answer 8

Radula contains magnetite, which is
magnetic;

Eyes on its shell