PHYLUM MOLLUSCA (Molle= soft body) Slide 2 PHYLUM MOLLUSCA OVER
100,OOO LIVING SPECIES; MANY 1000S OF FOSSIL SPECIES FOUND IN
ALMOST ALL ENVIRONMENTS: MARINE, FRESHWATER, TERRESTRIAL INCLUDES
SNAILS, SLUGS, CLAMS, SQUIDS, OCTOPUSES, Slide 3 CHARACTERISTICS
Body Plan: three main parts- head, foot, visceral mass body is
unsegmented Slide 4 Mantle - specialized tissue, secretes shell,
may be involved in feeding, reproduction and respiration Radula for
rasping; in all but one class CHARACTERISTICS Radula closeup Slide
5 ALL ORGAN SYSTEMS ARE PRESENT Circulation - Open (Hemocoel) -
Hemocyanin Respiratory System - gills (Ctenidia), lungs, mantle,
epidermis Osmoregulation - Metanephridia also excretion Slide 6
Feeding - Radula (scraping) Bivalves - Filter feed Nervous System -
Complex system of Ganglia ALL ORGAN SYSTEMS ARE PRESENT Slide 7
Reproductive System - usually dioecious, monoecious in some Marine
forms have free living trochophore larva Other larval stages may be
present ALL ORGAN SYSTEMS ARE PRESENT Slide 8 MOLLUSCAN CLASSES
Slide 9 Class Monoplacophora one plate all known from deep marine
waters (>12,000 feet) have a single circular shell with radula
Slide 10 Class Polyplacophora many plates- (chitons) have 8
overlapping plates or shells reduced head, no eyes or tentacles all
marine; usually live on rocky shores have radula, gills external
fertilization scrape algae Slide 11 Polyplacophora Respiration -
Gills in pallial groove Circulation - Heart at posterior end -
single Aorta Excretion - Nephridia Nervous System and sense organs
- Ganglia and nerves Sub Radular organ - Feeding Esthetes - light
sensing Osphradia - Sampling water Slide 12 Polyplacophora
Reproduction - Sexes Separate Usually external fertilization
Trochophore larva Slide 13 Class Aplacophora without plates Rare;
lack shell; wormlike deep marine; burrowing species; predators
About 320 species, not much is known of them Your book separates
them into two separate classes: !Caudofoveata !Solenogastres Slide
14 Class Gastropoda Largest class of Molluscs Most important
feature is Torsion Slide 15 Torsion Twisting of body into loop
Perhaps adaptation of veliger larva Disadvantages: Reduction of
organs on right side Excretion - Mouth moves near anus Adavntages
Allows water to be drawn from the front Slide 16 Gastropod -
Locomotion Foot Ciliary action below the foot Operculum Swimming
Slide 17 Gastropod - Nutrition Herbivores - Radula Carnivores
Filter feeders NERVOUS SYSTEM Similar to Chiton - but in the shape
of 8 Slide 18 Class - Bivalvia Includes Calms, Oysters, Mussels Has
two Shells (Valves) Shell held together by Adductor muscle Head is
lost Filter feeders Mantle secretes the shell Slide 19 MOLLUSCAN
SHELL STRUCTURE Periostracum ; outer layer Prismatic; middle layer
Nacre; inside layer- mother of pearl Slide 20 BIVALVIA Locomotion
Foot (burrowers) Active swimmers (Scallops) Circulation Open system
Excretion Nephridia Slide 21 BIVALVIA Nervous System 2 pairs of
ganglia Sense organs (statocysts, ocelli, ospharidia) Reproduction
Sexes separate Internal fertilization Larva - Glochidium Slide 22
Class - Cephalopoda Includes Squid, octopus, Nautilus Most advanced
of Molluscs Well developed head and eyes Head has tentacles with
suckers Squids are largest of invertebrates Locomotion by jet
propulsion Slide 23 Class Scaphopoda (tusk shells) slender, tubular
shells open at both ends all marine have tentacles around mouth no
defined head no gills, respiration across mantle
