Mollusk & Segmented Worms Chapter 27

Mollusk: Phylum Mollusca Consist of slugs, snails & animals that once lived in shells on the beach Consist of slugs, snails & animals that once lived in shells on the beach Range from slow- moving slugs to jet propelled octopus Range from slow- moving slugs to jet propelled octopus

Mollusk Characteristics Most live in the ocean, on land & freshwater Most live in the ocean, on land & freshwater Some have shells Some have shells All are bilateral symmetry with coelom & 2 body openings All are bilateral symmetry with coelom & 2 body openings Have a muscular foot for movement Have a muscular foot for movement

Have a mantle A mantle is a thin membrane that surrounds the internal organs. A mantle is a thin membrane that surrounds the internal organs. In shelled mollusk, the mantle secretes the shell In shelled mollusk, the mantle secretes the shell

Mollusk live in a wide variety of habitats Ocean: oysters, mussels live attached to the ocean floor Ocean: oysters, mussels live attached to the ocean floor

Mollusk live in a wide variety of habitats Ocean : octopus swim freely Ocean : octopus swim freely

Mollusk live in a wide variety of habitats Land Dwelling: slugs & snails can be found in moist tropical & temperate climates Land Dwelling: slugs & snails can be found in moist tropical & temperate climates

Classes of Mollusk There are 7 classes of mollusk. There are 7 classes of mollusk. The 3 that include the most common are The 3 that include the most common are 1. Gastropoda 2. Bivalvia 3. Cephalopoda They look different on the outside, but they are similar on the inside They look different on the outside, but they are similar on the inside Bodies are composed of a foot, mantle, shell & visceral mass that contains organs Bodies are composed of a foot, mantle, shell & visceral mass that contains organs

Gastropod-One shelled mollusk “Stomach Footed Mollusk” Land snails, slugs & marine limpet (sea slug) Land snails, slugs & marine limpet (sea slug) Name comes from the way the foot is positioned under the rest of its body Name comes from the way the foot is positioned under the rest of its body Many are hermaphrodites Many are hermaphrodites Marine Limpet

Sea Slug Land Snail Land Slug

Body Structure Radula-a tongue-like organ with rows of teeth used to scrape, grate or cut food Radula-a tongue-like organ with rows of teeth used to scrape, grate or cut food Simple nervous system w/ small brain Simple nervous system w/ small brain Blood is pumped by the heart Blood is pumped by the heart Open circulatory system Open circulatory system Radula

Cross-Section of a Snail Gut Mantle Shell Foot Head Visceral mass Mantle Shell Foot

Shelled Gastropods Snails, abalones, & conchs Snails, abalones, & conchs May be plant eaters, predators or parasites May be plant eaters, predators or parasites Conchs Abalones

Gastropods without Shells Sea Slugs, & Slugs Sea Slugs, & Slugs Sea Slugs feed on jellyfish & use its nematocysts to repel predators Sea Slugs feed on jellyfish & use its nematocysts to repel predators Some secret strong unpleasant smelling mucus Some secret strong unpleasant smelling mucus They are bright in color They are bright in color

Bivalves-2 Shelled Mollusk “Muscle Footed Mollusk” Oysters, Clams & Sea Scallops that have a 2 hinged shell Oysters, Clams & Sea Scallops that have a 2 hinged shell They strain their food from the water They strain their food from the water Do not have a distinctive head or radula Do not have a distinctive head or radula Strong hinge allows the shell to open and close Strong hinge allows the shell to open and close

Bivalves use cilia to beat & draw in water over the gills pushing food particles to the stomach

Cephalopods-Head footed mollusk Predatory squid, octopus & the chambered nautilus Predatory squid, octopus & the chambered nautilus Have sharp eyesight, muscular tentacles, jet propulsion, complex brain & ability to learn Have sharp eyesight, muscular tentacles, jet propulsion, complex brain & ability to learn Closed circulatory system Closed circulatory system

Octopus & Squid Often apply their intelligence to capturing prey or avoiding harmful situations Often apply their intelligence to capturing prey or avoiding harmful situations Instead of muscular foot, have tentacles w/ suckers for moving & capturing food Instead of muscular foot, have tentacles w/ suckers for moving & capturing food Octopus in a coconut shell

Octopus

The Octopus Octopus have separate sexes Octopus have separate sexes Make adapted to transfer sperm into the females body Make adapted to transfer sperm into the females body Fertilization is internal, eggs laid outside the body Fertilization is internal, eggs laid outside the body Use “ink” it confuse predators Use “ink” it confuse predators

Squid Squids are known as "the ice cream cone of the sea" because they are a favorite food of many ocean dwellers Squids are known as "the ice cream cone of the sea" because they are a favorite food of many ocean dwellers Backbone & ink sack used to write with Backbone & ink sack used to write with

Cross-Section of a Squid Tentacle Arm Head Mantle Gut Visceral mass Mantle Shell Foot

Chambered Nautilus Only shelled member of the cephalopod family Only shelled member of the cephalopod family

Segmented Worms: Phylum Annelida

Segmented Worms Include Bristle worms, Earthworms, and Leeches Include Bristle worms, Earthworms, and Leeches Term annelid means “tiny rings” Term annelid means “tiny rings” Bilateral & coleom with 2 body openings Bilateral & coleom with 2 body openings

Characteristic of Annelids All Annelids Are made of segments All Annelids Are made of segments Bodies appear to be divided into rings Bodies appear to be divided into rings Segmentations continue internally Segmentations continue internally Each ring is its own muscle-helps shorten & lengthens Each ring is its own muscle-helps shorten & lengthens

Parts of the Earthworm Setae Nerve IntestineGizzard Crop Aortic arches Brain

Parts of the Earthworm Mouth: takes in soil, beginning of the digestive tract Mouth: takes in soil, beginning of the digestive tract Crop: holds soil before it is passed to the gizzard Crop: holds soil before it is passed to the gizzard Gizzard: grinds food into small pieces so it can be absorbed. Gizzard: grinds food into small pieces so it can be absorbed. Setae: helps earthworm move by providing a way to anchor their bodies in the soil Setae: helps earthworm move by providing a way to anchor their bodies in the soil Circulatory system: closed Circulatory system: closed Nervous system: nerve fibers connected by ventral nerve cord to a simple brain Nervous system: nerve fibers connected by ventral nerve cord to a simple brain Nephridia: excretory structure Nephridia: excretory structure

Where do they live? Everywhere except in frozen soils of polar regions & dry sand like soils of the desert

Bristleworms: Mostly marine organisms Mostly marine organisms Have distinctive head with eyes & tentacles Have distinctive head with eyes & tentacles Each body segment has a pair of appendages called parapodia which are bristle like structures Each body segment has a pair of appendages called parapodia which are bristle like structures

Earthworms Are nocturnal animal Are nocturnal animal Come to surface but stay close to their burrows Come to surface but stay close to their burrows Cool moist soil provides protection during the day Cool moist soil provides protection during the day Water in the soil is a source of oxygen that soaks into the body through the skin Water in the soil is a source of oxygen that soaks into the body through the skin

Earthworms are hermaphrodites 2 worms exchange sperm 2 worms exchange sperm Each worm forms a capsule for the egg & sperm Each worm forms a capsule for the egg & sperm The eggs are fertilized in each worms capsule & slipped off into the soil The eggs are fertilized in each worms capsule & slipped off into the soil 2-3 weeks young emerge 2-3 weeks young emerge

Leeches Segmented worms with flatten bodies & no bristles Segmented worms with flatten bodies & no bristles Found in different habitats mostly fresh water Found in different habitats mostly fresh water Have front & rear suckers Have front & rear suckers Parasites that suck blood Parasites that suck blood

OUCH!!! The bite is not painful b/c the saliva contains a chemical that acts as an anesthetic The bite is not painful b/c the saliva contains a chemical that acts as an anesthetic Keeps blood from clotting & increase blood flow Keeps blood from clotting & increase blood flow Can ingest 2-5 times its own weight in one meal Can ingest 2-5 times its own weight in one meal Once fed-it may not eat again for a year WOW! Once fed-it may not eat again for a year WOW!