1. Molluscs
PAges

3. Overview Phylum mollusca Protostome
1st embryonic opening becomes mouth
Includes Annelids and Arthropods

5. Body structure Visceral mass – soft bodied, contains internal organs
Foot – strong, muscular portion; used for locomotion
Mantle - membranous/muscular covering enveloping visceral mass
Mantle cavity is space between mantle folds
May create shell

7. Also have head region with eyes and sense organs
Classified by foot modification:
Gastropods
Cephalopods
Bivalves

9. NudiBranchs, conchs, and snails
Gastropods
NudiBranchs, conchs, and snails

10. Foot is ventrally flattened Movement by muscle contractions along foot
Nudibranchs ("sea slugs") lack shells
Conchs and snails have coiled shells
Where visceral mass follows
Land snails have mantles with blood vessels, function as a lung

12. octopuses, squids, and nautiluses
Cephalopods
octopuses, squids, and nautiluses

13. Body structure Means "head-footed" No shell
Foot evolved tentacles around head
Beak and radula (toothy tongue)

16. Response to stimuli Cephalization
Eyes have lens/retina with photoreceptors
Brain formed by ganglia fusion with nerves connecting to parts of body

17. Movement Nerves control rapid contraction of mantle
Allows quick movement by jet propulsion

18. Clams, oysters and scallops
Bivalves
Clams, oysters and scallops

19. Body structure Shells made of 2 parts
Secreted by mantle (made of protein no calcium carbonate)
Valves held together by adductor muscles

21. Feeding and digestion
Organs include mouth, labial palps, esophagus, stomach, intestine, and kidneys
Filter feeder
Siphon draws particles into mantle cavity
Siphon – posterior opening between 2 valves
Mucous secretions collect particles around gills
Ciliary action sweep towards mouth

23. Circulatory system Coelom is reduced
Heart located below hump of shell (pericardial cavity)
Pumps blood into dorsal aorta, then to organs
In organs, blood flows through sinuses
"Open circulatory system"

25. Nervous system
Consists of 3 pairs of ganglia (anterior, foot, posterior)
Connected by nerves
Lack cephalisation

27. Excretory system 2 excretory kidneys beneath heart
Remove waste from pericardial cavity into mantle cavity

29. Locomotion "hatchet" foot extends from anterior of shell
Expands tip of foot, pulls body forward

30. Reproduction Sexes usually separate
Gonads (ovary or testis) around intestine coils
all Have a larval stage