Introduction Clam Oyster Snail Octopus Squid Write down as many facts as you can about these five animals Write a sentence at the bottom of the page telling what you think all these animals have in common

Phylum Mollusca Chapter 27-1 Pages

Chiton – relatively primitive marine mollusk. Shell made up with a number of plates Squid - at 24 feet, this female squid is not fully grown, so it's relatively small by giant squid standards. The longest one on record is 60 feet, researchers say.

An octopus eating a crab

General Characteristics Second largest animal phylum Share similar developmental patterns Special larva: trochophore Swim in open water Feed on tiny floating plants Coelomates 3 tissue layers Bilateral symmetry Level of organization: organ

General Characteristics Soft-bodied animals that have an internal or external shell Body is composed of 4 distinct parts: Visceral mass Foot Mantle Shell

General Characteristics Foot Contains a mouth for feeding Flat surface adapted for crawling Spade-shaped for burrowing Tentacles for capturing prey Mantle Thin, delicate tissue that covers most of it’s body, like a jacket Shell (skeleton) Made by glands (secrete CaCO3) in the mantle Visceral mass Underneath the mantle Contains internal organs (digestive tract, kidneys, reproductive organs, nerve cords, cephalization) For locomotion

ARE SQUIDS BILATERAL OR RADIAL?

7 Essential Life Functions Feeding: herbivorous, carnivorous, filter feeders, detritus feeders, parasitic Symmetry: bilateral Movement: motile and sessile Response: ganglia, nerve cords, sense organs, statocysts, ocelli, memory Reproduction: separate genders, external/internal fertilization Internal Transport: open and closed circulatory system Respiration: gills – organ for respiration Excretion: undigested waste thru the anus, metabolic waste thru nephridia

Feeding Herbivorous Carnivorous Filter feeders Clams, oysters, scallops Use gills to sift food Detritus feeders Parasitic Use radula - tongue shaped structure - a layer of flexible skin that carries hundreds of tiny teeth (like sandpaper) only a few species Show video

Response Sessile (ie Clams) Burrow in mud or sand Simple nervous system Small ganglia near mouth, nerve cords Touch receptors, statocysts, ocelli Motile (ie Octopus) Highly developed nervous system Well developed brain Good memory Sense organs Distinguish shape by sight Distinguish texture by touch Show video

Reproduction **Separate genders Release eggs and sperm into open water External fertilization Free-swimming larva (trochophore) develops Hermaphrodites Internal fertilization (inside female’s body) Snails pair up and fertilize each other’s eggs Oysters will switch genders

Internal Transport Oxygen and nutrients are carried by blood to all parts of a mollusk Blood is pumped by simple hearts Sessile/Slow-moving mollusks (Clam, oysters) Open circulatory system Blood does not always travel inside vessels Fast-moving mollusks (octopus, squid) Closed circulatory system Blood always travels inside vessels

open closed

Respiration Aquatic Gills (a pair) Located inside their mantle cavities Terrestrial Specialized mantle cavity lined with many blood vessels Needs to be moist

Keeps animal closed Comes in a pair - For locomotion - For digging

Excretion Anus Removes undigested food In feces form Nephridia Removes metabolic wastes In ammonia form

3 Classes Gastropod “ stomach – foot” Snails and slugs Bivalves “two - shelled” Oysters, clams, scallops Cephalopods “head – foot” Squid, octopus

Gastropod Without a shell Spend the day hiding under rocks Spend the night feeding Could have ink-producing glands Some have one-piece shell to protect soft bodies Some are poisonous Eg. snails, sea hare, slug Sea hare

Bivalve Have 2 shells hinged together by strong muscles Free-swimming Burrow into mud or sand Mostly sessile, some can move by flapping their shells Protect their bodies by secreting nacre that wraps around the foreign object (sand, small pebble) The beginning of a pearl

Cephalopod Head is attached to its foot Most have 8 tentacles (feet) Small internal shell or none at all For protection: Release dark-coloured ink Poison Camouflage Squids, octopus, cuttlefish

Ecological Role Filter feeders can clean up their surroundings Food for other organisms Environmental monitors Herbivorous mollusks will damage crops Don’t eat shell-fish that is contaminated. It will make you SICK! Homework: Read Questions 1, 2, 4