Mollusk / AnnelidsMollusk / Annelids

Mollusk

History of WormsHistory of Worms

• Identify the characteristics of mollusks.

• Compare the adaptations of gastropod, bivalve, and cephalopod mollusks in their biomes.

Section Objectives:Section Objectives:

Phylum MolluscaPhylum Mollusca

• Snails, clams, squids, slugs and oyster are examples.

• Found freshwater, ocean or moist terrain.

Bilateral symmetry -Bilateral symmetry -

• Distinct regions mirrored on a left and right axis.

9 Structures9 Structures

1. Radula1. Radula

• Tongue like organ that protrudes from the mouth used for eating algae. Contains rows of tiny teeth that are used for scraping algae from surfaces.

• A radula may have as many as 250,000 teeth.

RadulaRadula

Radula

2. Mantle2. Mantle

• soft, moist layer inside the shell of mollusks.

Mantle

3. Shell3. Shell

• outer layer.

• Most made of calcium carbonate. CaCO3

Shell

4. Gills4. Gills

• gas exchange occurs through the mantle and the gills.

• Gills also filter food particles from the water.

5. Foot5. Foot

• extends out and helps with movement.

Foot

6. Heart6. Heart

• Has a 3 chambered heart.

• a. Open circulatory system - blood moves through vessels and into spaces around the body organs.

• Ex: Snails, squid, and clam

6. Heart6. Heart

• b. Closed circulatory system - blood moves through the body enclosed entirely in a series of blood vessels.

Some mollusks, such as octopuses, move nutrients and oxygen through a closed circulatory system.

Mollusks have a well-developed circulatory system that includes a three-chambered heart.Mollusks have a well-developed circulatory system that includes a three-chambered heart.

Heart

7. Siphons7. Siphons

• act as devices to let water in and out of mollusks.

8. Nephridia8. Nephridia

• tube like structure that form the excretory system.

9. Visceral mass 9. Visceral mass

• area located between the muscular foot and mantle

• contains most of the internal organs.

Mollusk DiversityMollusk Diversity

• Form the second largest phylum. Contains 7 different types of mollusks.

• First animals to have evolved respiratory organs.

Classified accordingClassified according

• to shell type, muscular foot structure, and arrangement of internal body organs.

ChitonsChitons

• live on rocky surfaces in shallow water. Ex: Chitons ( KY - tunz)

• Most primitive mollusks, do not have a ganglia and have simple sense organs.

• live on rocky surfaces in shallow water. Ex: Chitons ( KY - tunz)

• Most primitive mollusks, do not have a ganglia and have simple sense organs.

ChitonsChitons

•Have 8 overlapping plates.

Snails and SlugsSnails and Slugs

• largest class of mollusks.

• Have a radula that scrapes up algae or tears apart plants or one piece shells.

• Have sense organs concentrated in the head region. Open circulatory system.

• Aquatic gastropods use gills as respiratory organs.

Snails and slugsSnails and slugs

• Ex: snails or slugs

snails

Sea slug

Bivalves Bivalves

• Do not have a head, have two shells attached by a hinge, have sense receptors, ganglia, most are marine, and do not have a radula.

• Filter feeders.

BivalvesBivalves

• Ex: clams, mussels, scallops and oysters

clam

mussel

scallop

CephalopodsCephalopods

• Tentacled mollusk modified head and foot regions.

• Have a highly developed nervous system, sense organs, usually no external shell, closed circulatory system and can usually swim fast.

OctopusOctopus

CephalopodsCephalopods

• Ex: squids, nautiluses, octopuses, Cuttlefishes. Most recently evolved mollusks.

squids

nautiluses octopuses

Cuttlefishes

CuttlefishCuttlefish

NudibranchNudibranch

MollusksMollusks

oysters

Octopus

MollusksMollusks

Trivia:Trivia:

• The largest-known squid was 57 feet (17.5 m) long.

1. In shelled mollusks, the ___________ secretes the shell.

2. Bivalves obtain food by ______________.

3. ______________ have two shells.4. The excretory structures that

remove metabolic wastes from the bodies of animals such as mollusks and annelids are called ________________.

Mantle

Bivalve

Filter Feeding

Nephridia

5. An animal whose blood moves throughout its body within blood vessels has a(n) ___________________.

6. The ____________ is a tongue like organ with rows of teeth that is used by gastropods to scrape, grate, or cut food.

7. The most complex and most recently evolved mollusks are _______________.

Closed Circulatory system

Radula

Cephalopods

8. What compound are most shells composed of?

9. ____________ are involved in removing wastes from a mollusk’s body.

10. Which animal is believed to be smarter a snail or a squid?

CaCO3 and SiO2

Siphons or Nephridia

Squid

AnnelidsAnnelids

AnnelidsAnnelids

• earthworms, leeches and many segmented marine worms.

• Classified by the presence or absence of setae or parapodia.

leech

brownBrown sea

worm

Ex: earthwormsEx: earthworms

•

Earthworm movementEarthworm movement

11 Structures or Systems of earthworm

11 Structures or Systems of earthworm

1. Setae1. Setae

Bristles that help classify annelids depends on the number and presence of the bristles.

Help to anchor each segment in the soil and help with movement.

2. Parapodia2. Parapodia

leglike structure

3. Nephridia3. Nephridia

excretes the wastes.

4. Crop4. Crop

temporary storage organ.

4

5. Gizzard5. Gizzard

• Grinds up soil , freeing the organic matter and breaking it down.

5

6. Intestine6. Intestine

• long , straight tube where organic matter digested.

• Eat their way through the soil. (Casting - earthworm’s waste)

6.

7. Circulatory system7. Circulatory system

• closed system.

• (Aortic arches - muscular structures that functions as simple hearts by contracting and forcing blood into the ventral blood vessels.

7

8. Respiratory system8. Respiratory system

• Gas exchange takes place across the skin. Skin must be moist for diffusion of oxygen to take place.

• Produce a mucous secretion and have an outer cuticle that helps keep skin moist.

9. Nervous System9. Nervous System

• has a small brain made up of fused ganglia

• At the anterior end of the digestive tract.

10. Reproductive system10. Reproductive system

• Reproduce sexually, are hermaphrodites, but cannot fertilize their own eggs.

• When mate join head to tail and secrete a mucus covering around the joined areas and each worm then releases sperm into a special sac in the other worm.

11. Skeletal system11. Skeletal system

• hydrostatic (fluid filled to hold shape).

Earthworm AnatomyEarthworm Anatomy

TRIVIA:TRIVIA:

• Earthworm eggs hatch in 2-3 weeks.

BristlewormsBristleworms

Fan Worms

bristleworm

BristlewormsBristleworms

• largest and oldest class of phylum Annelids.

• Gas exchange takes place across the surfaces of the parapodia.

• Are typically free swimming or tube dwelling marine annelids.

leechesleeches• usually freshwater

parasitic annelids.• Attach to host with

a pair of suckers or hooks.

Uses of Mollusks and Annelids

Uses of Mollusks and Annelids

• Mollusks (clams, oysters , etc are important food sources.)

• Annelids - by burrowing through the soil, help to loosen , allowing water and air to pass easier.

Doctoring with LeechesDoctoring with Leeches

Medical LeechMedical LeechThe medicinal leech is best known as the organism

used for blood letting (people used to believe many health problems caused by getting rid of "bad" blood). Surprisingly, they are being used once again to remove blood from hematomas (areas of blood leakage) resulting from surgery (like re-attaching severed limbs, etc.). The ability of the leeches to parasitize humans and other mammals depends on a variety of adaptations that allow them to pierce or cut into skin without notice.  Hirudo uses three sharp cutting plates (teeth) like circular-saw blades to make a Y-shaped incision in the skin.  While cutting the skin, it secretes an anesthetic as well as a histamine-like substance that keeps the blood vessels open. The blood is then sucked into the pharynx. While it is being swallowed, an anticoagulant protein called hirudin produced by the salivary glands is added to the blood to prevent it from clotting. After the salt-water from this blood is eliminated by the nephridia, the concentrated blood is stored in within numerous diverticula (outpocketings) of the crop called gastric caeca (ceca). The proteins of hemoglobin and other components of the blood are then digested extremely slowly (as long as 200 days), which provides enough energy to live another 100 days without feeding!  Surprisingly, the gut does not secrete digestive enzymes.  Instead, the leeches rely on bacteria in the gut for enzymatic digestion.  In the medicinal leech, a single species of bacterium digests the blood and also produces an antibiotic that eliminates any other bacteria from the digestive tract, allowing the red blood cells to remain unspoiled within the leech for up to a year! This also means that you don't have to worry about getting a bacterial infection from the leech!

Leeches therapyLeeches therapy

TrochophoreTrochophore

• ciliated, pear shaped larval form of mollusks and annelids.