Transcript Mollusks - Phillips Scientific Methods

Mollusks:
Phylum Mollusca
Invertebrates
Chart-notes
Mollusks
• Examples: snails, slugs, clams, squid,
octopus, oysters, scallops
• Phylum: Mollusca – “soft-bodied”
• Germ Layers: 3
• Body Symmetry/shape: Bilateral
• Segmentation: none
• Coelom: True Coelom
• Nervous: some simple; some complex
• Skeleton: some hydrostatic; some
Exoskeleton (shells)
The Mollusk Body Plan
Visceral mass-organs
Shell-protection
Squid
Snail
Shell
Mantle cavity
Foot
Clam
Early
mollusk
Foot- movement
Mantle-thin membrane surrounding organs
Gills
Digestive tract
Mollusks
• Digestion: varies: herbivores, carnivores, filter
feeders, detritivores, or parasites
• Excretion: tube-shaped nephridia
• Circulation: some have open system, some have
closed open- sinuses, simple vessels, simple heart
• Closed- complex blood vessels, complex heart
• Respiration: aquatic-gills; land-moist mantle
• Reproduction: all sexual; some hermaphrodites
a. Internal Fertilization- eggs fertilized inside
b. External Fertilization- eggs fertilized outside
3 Classes of Mollusks
1. Class Gastropoda – “stomach foot”
2. Class Bivalvia – “two shells”
3. Class Cephalopoda – “head foot”
1. Class Gastropoda – “stomach-foot”
• Shell-less or single shelled
• Examples:
snails, slugs, sea slugs
• Body Processes:
a. Digestion:
- radula – tongue-like organ
- teeth to scrape & cut out food
b. Nervous System – small brain
c. Open Circulatory System
d. Respiratory – gills(aquatic), primitive lung,
or diffusion through skin(land)
*** may secrete slime to help
in movement and breathing
Snail Exterior
Sea Slugs
2. Class Bivalvia – “two shells”
• Bivalves have 2 shells held together by one or
two powerful muscles
• Examples: Clams, oysters, scallops, and mussels
clams
oysters
scallop
Body Processes:
a.
Movement
- mostly remain in one place (especially
oysters)
- clams use foot to burrow into sand and
escape from predators
https://www.youtube.com/watch?v=ALaMoS_vvNE
Slide 11
- mussels use sticky thread to attach to
rocks
- scallops can move rapidly by flapping
shells
b. Digestion – filter feeders
c. Respiration – filter oxygen from the water
using gills
d. Circulation – open
e. Reproduction – sexual, hermaphrodites
foot
siphons
3. Class Cephalopoda – “head foot”
• most complex/ most active mollusk
• head attached to foot that is divided up into
tentacles
• Examples: octopus, squid, cuttlefish, & nautilus
•Body Processes of Cephalopods
a. Digestion
- radula & sharp beak-like jaws
- tentacles with suckers- capture prey/movement
**these adaptations make them effective
marine predators
b. Respiration – gills
c. Circulation – closed circulatory system
d. Reproduction: sexual
- separate sexes
- internal fertilization; eggs put outside of
body
e. Nervous System
- large brain
- good eyesight
- tentacles very sensitive to touch
f. Movement
- jet propulsion – squirts
water out of siphons (holes
in the side of the head)
g. Defense
- can change colors
(used for camouflage &
communication)
- can expel ink if threatened