Download Mollusks

Mollusks
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Class: Bivalvia
Class: Cephlapoda
Characteristics
_______largest phylum
125,000 living species; 35,000 fossil species
_____________________
Soft body
Habitat
______________________(mostly marine, some freshwater), some moist
terrestrial habitats
Most are _____________________ and creep SLOWLY on a ventral muscular foot,
some are free swimming
Importance
Food, pearls, cultivated plant damage, intermediate hosts for parasitic worms, ship
damage (ex. wharves, pilinings)
Body Structure
_____________________
Coleom present
_____________________
2 body openings
Structure
_____________________: located in mouth,
tongue-like organ with rows of teeth, used to scrap, drill, grate or cut food
Bi-valves are filter feeders, (no radula)
Digestion
_____________________ digestive system
(mouth stomach  intestine anus)
_____________________: filter feeders, burrow in sand & use cilia to beat water
through incurrent siphon (gill-like structure) and push food to stomach
Gastropods & Cephalopods are predators
Nervous system
_____________________ nervous system
Brain & associate nerves
Most have paired eyes
Range from simple cups that detect light to complex eye (retina, pupils, irises)
Circulatory System
_____________________: blood flows through vessels into open spaces around body
& over organs (most mollusks)
_____________________: blood enclosed in vessels (squid & octopi)
Heart has 2 chambers (one atrium and one ventricle
Respiration
Marine mollusks have one, to many, _____________________
Terrestrial mollusks have a “lung” (not a true lung)
Gas exchange also takes place through epidermis (skin)
Reproduction
_____________________: most species have male & female, few are hermaphrodites
Mollusk Classes
Class: Gastropoda
Examples: Snails, slugs, whelks, conks, abalone
Most are marine, a few live in freshwater or on land
Structure
 Conspicuous head with two pairs of retractile tentacles, a pair of eyes and a mouth
Head joins directly to a long ventral muscular foot
 On top of foot there is a shell (one piece and is unchambered)
 Shell is spirally coiled and asymmetrical
 Soft parts can be drawn up into shell
Class: Bi-valva
Examples: Clams, mussles, scallops, oysters
Mostly marine, a few fresh water species
Structure
 Hard shell, symmetrical halves joined by an elastic hinge ligament
 Shell is secreted by mantle & is made of three parts
o Periostracum – (top layer) horny covering that prevents parts underneath from being
dissolved
o Prismatic – (middle layer) layer of crystalline calcium carbonate
o Nacre – (inner layer) mother of pearl, formed by thin layers of calcium carbonate
Class: Cephalopoda (head-foot)
Examples: Octopus, squid, cuttlefish, chambered nautilus
 Foot has evolved to have tentacles with suckers
 Grab food & use for movement
Structure
 Most advanced invertebrates
 Cartilage “brain box”, vertebrate type eyes, separate pancreas
 Simple eyes (do little more than detect light and shape)