Chapter 29: Mollusks and Annelids

What is a mollusk?What is an annelid?

Mollusks

Objectives:

• Describe the skeletal structure, fertilization, reproduction, body symmetry, body coverings and locomotion for the Phylum Mollusca and Phylum Annelida

• This will be completed through spreadsheet notes…..

How are annelids and mollusks related?

• Both were the first major groups of animals to develop:

• true coelom. – they have a body cavity, the gut and the rest of the organs are cushioned by the fluid in the coelom.

• trocophore: a larval stage develops from egg, in some species it is free swimming and propels itself with cilia.

Trochophore: Free swimming larval stage of mollusks and

annelids

Seven classes of mollusks make up phylum Mollusca

• Three largest classes and examples are:

• Gastropods- snails and slugs• Bivalvia- clams, oyster, and scallops• Cephalopoda- octopuses and squids

Know the 6 Key Characteristics of Mollusks

• 1. Body cavity: true coelom• 2. Symmetry: bilateral symmetry• 3. Three-part body plan: visceral mass-

central part, mantle- outer layer of body, foot- muscular region used for locomotion

• 4. Organ systems- excretion, circulation, respiration, digestion, reproduction

• 5. Shell- one or two shells (most)• 6. Radula- tongue like organ in the mouth,

thousands of teeth on radula scrap off food and pull in prey.

Animal Skeletal structurePhylum

Mollusks:3 part body plan

most have shells, (foot, visceral mass, mantle)

Fertilization and Reproduction: Molluskshas reproductive system, male and female individuals, some hermaphrodites

Important Features : Mollusksorgan systems for excretion circulation, respiration, reproduction, two ends to digestive tract, radula for feeding

Body symmetry: Mollusksmost bilateral

Body coverings: Mollusksmost have either one or two shells, mantle of tissue covering body

Locomotion: Mollusksmuscular "foot" used to dig, slide, jump

Mollusk - Gastropods Examples: snails, slugs

Fertilization and Reproduction for Gastropods: same as mollusks

Important Features (look in this column and fill in for gastropods)

have organ systems for excretions, circulation, respiration, reproduction, two ends to digestive tract, radula for feeding

same as mollusks, pair of tentacles on head with eyes at tips

Body symmetry of gastropods is bilateral

Body coverings of gastropods are a mantle of tissue covering

the body, spiral shells

Locomotion of Gastropods:"foot", secretes

mucus it glides on

Bivalves: Examples: clams, oysters, scallops (all the notes for the next 6 slides

are in the bivalve row)

Bivalve skeletal structure:

• All have two part hinged shell

Giant clams can weigh more than 227 kilograms (500 pounds), and are the largest bivalve mollusk in the world.

Fertilization and Reproduction of Bivalves:

sexually, release sperm and egg into water, fertilized eggs become trocophore larvae

Important features of Bivalves:filter feeders, through siphon tube, over gills out other siphon tube

Body symmetry of bivalves is bilateral

Body coverings of bivales: two part hinged shell, two thick

adductor muscles connect shells

Locomotion of bivalves: most sessile, some swim

opening/closing valves quickly

Cephalopod examples: squids, octopuses, cuttlefish, nautilus

Cephalopod skeletal structure:large head attached to

tentacles, lack external shell,

Cephalopod reproduction: Sexual

Cephalopod body symmetry: bilateral

Cephalopod body coverings: only nautilus has shell

Cephalopod locomotion: jet propulsion

Animal Skeletal structure

Annelids:

segmentation, setae: bristles, some have parapodia: fleshy appendages

Annelids:

Fertilization and Reproduction of Annelids:hermaphrodites, reproduce sexually

Important features of annelids: respire through skin, have closed

circulatory system, complex nervous system

Body symmetry of Annelids: bilateral

Body coverings of annelids: setae: bristles, some have

parapodia: fleshy appendages

Body coverings of annelids: setae: bristles, some have

parapodia: fleshy appendages

Locomotion of annelids: fluid filled compartment aids with

contracting, stretching to move

Marine worms: Examples feather dusters, Nereis

Marine worm skeletal structure: Many parapodia

Marine Worm Reproduction: Hermaphrodites, sexual

Marine worm special features:some burrow, others live in protective tubes, some feed by pumping water through body

Body symmetry of Marine worm: Bilateral

Body coverings and locomotion of marine worms: many parapodia, use parapodia to swim, burrow or crawl

Earthworms skeletal structures: no parapodia, only

setae

Fertilization and Reproduction of Earthwormshermaphrodites, reproduce sexually

Important Features of Earthworms: eat their way through soil

Symmetry, body coverings, locomotion of Earthworms:

bilateral few setae on each segment

fluid filled compartment aids with contracting, stretching to move

Leeches Skeletal Structure and Reproduction:

LeechesExamples:

suckers on both ends of body, flattened body

hermaphrodites, reproduce sexually

Important Features, Symmetry and Body covering of Leeches

most species predators or scavengers

bilateral lack both setae and parapodia

Locomotion of Leeches:contraction and elongation of

body

Let’s Review!

• Get out the worksheet titled Invertebrate Review: Cnidarian, Annelids, Molluscs

We have covered the Phylum of Sponges, Cnidarians, Annelids,

and Mollusks

• Over the next few slides, determine what phylum the animal is classified.

• Write the name of the animal under the correct heading on your worksheet.

• Write a sentence about the characteristics of each animal.

Slide 1: Earthworm- look at the example of the sentence for

characteristics.

Slide 2: Sea AnemoneCharacteristic example: all

polyps, have tentacles

Slide 3: Sponge Characteristic: Is

asymmetrical, is sessile

Slide 4: hydrozoan has stinging tentacles, radial

symmetry, formed of both polyps and medusa

Slide 5: gastropod, has a single shell or no shell

Slide 6: Leech suckers on both ends of body, segmented

flattened body

Slide 7: cephalopod has 3 part body plan, organ systems,

radula

Slide 8: Feather Dusters have many parapodia,

segmentation,

Slide 9: Scyphozoan has both polyp and medusa stage,

radially symmetric

Slide 10: Bivalve two part hinged shell, bilateral, filter

feeder

Slide 11: Sponge have spicules and spongin for

support

Slide 12: Sponge have ostia and oscula as body coverings

The Walrus and the Carpenter enjoyed Bivalves…..

End of Critter Quiz!

• Pass in your slide show notes

• Pass in your quiz

• Ready for a movie and quiz?

Humans are big fans of bivalves too.

Buried Bivalve

Marine Bivalves

1. What class of animals are they!

Giant Squid – a cephalopod

Nautiluses - Cephalopods

Pearly Nautilus

Cuttlefish

Octopus - cephalopods