Worms & Mollusks

Mrs. Wetzel Biology

Review• 5 kingdoms

- Prokaryotes *- Protista *- Fungi *- Plants * - Animals

Review• Animal Kingdom

– Invertebrates• Porifera *• Cnidarians *• Worms• Molluska• Arthropods• Echinoderms

Review• Vertebrates

– Fish– Amphibians– Reptiles– Mammals

Worms

• Three Phyla of worms– Platyhelminthes

• Flatworms– Nematoda

• Round worms– Annelida

• Segmented worms

Platyhelminthes• Flat worms

–Flatworms are soft flattened worms that have tissues and internal organ systems.

–They are the simplest animals to have three germ layers, bilateral symmetry and cephalization

Platyhelminthes• Examples of

flatworms are– Planaria– Flukes– Tapeworms

Platyhelminthes• Respiration,

circulation, excretion all depend on diffusion.

• Flame cells are specialized to remove waste

Platyhelminthes• Response-

– Platyhelminthes have a collection of nerve cells near the head called ganglion. They are not complex enough to be called a brain.

– Eyespot is also found on flatworms. It is used for detecting light

Platyhelminthes• Movement- Flatworms move using

cilia found on epidermal cells, or by twisting in the water

Platyhelminthes• Classification-

– Turbellarians- free living in water

– Bottom dwellers eat decaying material on the bottom

– Most famous = planaria

Platyhelminthes• Classification

– Trematodes- parasitic– Most famous = flukes

Fluke Life Cycle

Platyhelminthes/Flukes • Schistosomiasis- rampant in areas

with poor sewage systems (pee/ poo where you drink/ bathe)

• Schistosomiasis eggs accumulate in the blood vessels clogging heart & causing tissue decay

• * Parasitic flat worms have a slightly thicker coating that protects them from being digested by their host= tegument

Schistosomiasis

Platyhelminthes• Classification- Cestoda aka

Tapeworm• Live inside the intestine of the host• Attach with the scolex

Nematoda• Nematodes= Roundworms

Nematoda• Feeding- many are free living

carnivores that can live in moist soil, some are marine

Nematoda• Respiration/ Circulation/ Excretion

– There is NO internal transport system, they depend on diffusion for transporting cellular metabolic waste such as ammonia.

Nematoda• Response= Ganglia same as

flatworms (platyhelminthes)

Nematoda• Reproduction= Sexual

TrichinosisAdult worms live and mate in the

intestine of the host- eggs are released and burrow into the intestinal wall. The larva then travel into the bloodstream and organs causing pain. The life cycle is complete when something ingests the muscle infected with tissue infected with eggs

Filarial Worms• Elephantiasis is cause when a large

number of filarial worms block the passage of fluids within the lymph vessels of a part of the body

Ascarid Worms• Ascaris matures in the intestine of the

host reaching up to 50 cm. The Ascaris causes severe malnutrition in more than 1 billion people worldwide

Hookworms• Hookworms live in the soil and enter

the body through an exposed foot. They then borrow into the bloodstream where they set up shop sucking the blood of their host causing weakness and poor growth

Phylum Annelida• Segmented worms

– Animals with segmented bodies and a true coelom lined with mesoderm

Phylum Annelida• Feeding and digestion- feeding

varies• Annelids pull food into the pharynx it

is then stored in the crop then eventually pushed down into a gizzard where it is ground up and digested

Phylum Annelida• Annelids have a closed circulatory

system! Blood is circulated through a series of blood vessels

Phylum Annelida• Respiration- Marine annelids breath

through gills• Terrestrial annelids have very moist

skin which allows for gas exchange on the epidermis.

Phylum Annelida• Excretion-

– Solid waste is passed through the anus– Liquid waste is filtered from the blood

by nephridia

Phylum annelida• Movement

– Longitudinal Muscles & circulatory muscles contract alternately allowing the worm to move

– Marine annelids have parapodia= paddles

Phylum Annelida• Reproduction

– Sexual– Asexual– Hermaphrodites- worms rarely fertilize

themselves. Usually two worms will attach at each others clitellum and drop off some sperm. When eggs are ready to be fertilized the stored sperm from the other worm will be used. The thicken clitellum will then slip off of the worms body with the fertilized eggs and create a cocoon

Phylum Annelida• Classification

– Oligochaetes- earth worms– Hirudinea Leeches- external parasites– Polychaeta- marine worms

Phylum Molluska• One of the oldest and most diverse

Phyla• Soft bodies animals with an internal

or external shell

Phylum Molluska• Body Plan- usually soft bodies

animals with an internal or external shell– Shell– Visceral Mass– Mantle Cavity– Foot

• Molluska and annelids are closely related as their larva is similar

Phylum Molluska• Feeding- herbivores, carnivores, filter feeders, detritivores,

parasites – Snails & Slugs eat using their radula – looks like a big tongue– Octopi can produce toxins to poison their prey and then pull

them into their jaws using their tentacles

Phylum Molluska• Respiration- • Aquatic Mollusks breath using gills• Terrestrial animals breath through

gas exchange over the mantle cavity

Phylum Molluska• Circulation- open circulatory system-

organs are bathed with blood in sinuses

Phylum Molluska• Excretion- Nephridia removes

ammonia

Phylum Molluska• Response- Varies greatly

– Bivalves- pretty simple small ganglia– Gastropods- small antennae that can

sense their environment – Cephalopods- Highly developed brain

• Can remember things• Reward & Punishment

Phylum Molluska• Movement- varies

Phylumn Molluska• Reproduction-

– Sexual– Asexual– Hermaphrodites

Phylum Molluska• Classification

- Bivalves; Clams, mussels, oysters- Gastropods; Snails, slugs- Cephalopods; Octopus, squid, nautilus.

Gastropods

Bivalves

Cephalopods