Video

• ..\..\..\Lesson Videos\Biology 11\Gold Mines Unearth Worms From Hell.flv

Battle of The Worms

The Combatants

Platyhelminthes AnnelidaNematoda

FLAT

ROUNDSEGMENTED

What can we say about the appearance of the various worms?

Notice where they each are.

Are Platyhelminthes the first bilateral animal?

• Two-way gut (no anus)• No circulatory system• No coelom (acoelomate)• Simple excretion with he

help of flame cells.

Platyhelminthes

• There are more than 20,000 species of Platyhelminthes. They range from brilliantly colored creatures that swim in the ocean to parasitic flatworms that live inside the bodies of an estimated 200 million humans around the world.

Lets measure up the phylaFirst up: Platyhelminthes

OVERVIEW• Un-segmented body plan • Flat• Carnivores or Scavengers• CEPHALIZATION• Many are parasites (feed on blood, tissue, cells

in host)• Lack circulatory, respiratory, & excretory system• Why are they so flat?• Triploblastic but no coleom

DIFFUSION MACHINES!

Digestive system•Pharynx (muscular tube to suck food)•Intestine (with enzyme assisted digestion)•Gastrovascular cavities increase absorption of food into blood.•Only MAJOR difference from Cnidarians is?•Muscular Pharynx

Important parts. Notice the mouth will not always be located at the head!

Video

• ..\..\..\Lesson Videos\Biology 11\Planarian.flv• http://www.youtube.com/watch?

v=w0QzSYQGsnA

The first head.

• Scientists believe that flatworms were the first creatures to develop heads.

• Two nerve chords run the length of the animal.

• Eye Spots/ Oceli

First Brain

• Ganglia - nerve clusters are found in the head.

Despite having more developed nervous system and a head, Platyhelminthes has strong regenerative powers.

Remember the sponge anyone?

Certain classes of flatworms can be chopped up as shown below and will regrow in the following ways.

Why do we get each of the following outcomes?

Has to do with cell differentiation and chemical messages. Undifferentiated cells will grow into their specific tissue type depending on chemical messages received from neighboring cells. That’s why we see the results we do. Cells near head will have more pressure to develop into brain and head cells, therefore larger head to body ration than situation 2.

Excretion• Specialized FLAME CELLS function like

kidneys.• Capture water and waste, beating of cilia

propels wastes to exterior of the worm.

Reproduction

Asexual• Can reproduce by splitting,

“fission,” and re-growing.• Hermaphroditic and

reproduce with themselves with sperm and egg

Sexual• Often meet to swap sperm

and eggs.

Triploblastic tissue development and Flame cells: close up.

Parasitic flatworm adaptations

• Some have NO digestive tract and rely on hosts to absorb via diffusion. This is why they live in the gut of animals.

• Food is already broken down and easily absorbed via diffusion.

• Some lose Ocelli (eyespots)• Develop complex life cycles relying on various

hosts.

Class Cestoda (The Tapeworm)

Tape worm in the stomach, attached to the stomach wall.

Tapeworm (class Cestoda)

• can be up to 18 m long!• weakens, but doesn’t kill host• live in intestine of vertebrate animals• has a scolex = at the head, suckers and a ring of

hooks to attach to intestinal wall• body sections containing a full set of male and

female sex organs • absence of digestive tract makes room for

hundreds of thousands of eggs

Species Examination: Taenia solium

• T.solium is a parasitic tapeworm of the phylum Platyhelminthes and Class Cestoda.

• Please do the reading and answer the questions for discussion.

The life cycle of the pork tapeworm.

Will you ever eat pork again?

• The pork tapeworm• ..\..\..\Lesson Videos\Biology 11\Later Inverte

brates\Monsters Inside Me_ Pork Tapeworm.flv

Tape worm diet. Are you kidding?

..\..\..\Lesson Videos\Biology 11\Later Invertebrates\ tapeworm diet expert.flv

Planarians (a non parasitic Platyhelminthe) and Stem Cell research

• Reading

• Stem cell video: ..\..\..\Lesson Videos\Biology 11\Later Invertebrates\Life-saving research in to stem cells - Horizon - BBC.flv

• Show video on Planarians.

http://www.youtube.com/watch?v=J9EuFuJF9N0&feature=related

..\..\..\Lesson Videos\Biology 11\Later Invertebrates\Planarian Regeneration Part 1.mov.flv

Review sheet of Platyhelminthes

• Worksheet review: Platyhelminthes

Phylum Nematoda (roundworms)

How many roundworms (or nematodes) do you think are in a rotten apple?

90,000

Overview: Nematoda • Most of free-living, some are parasitesDIGESTION• First to have a complete, straight digestive track

(mouth to anus) increase efficiency!!• Carnivores- eat small animals, algae, fungi; some

detritus feeders• Some are parasites of plants (crops, fruits) and

animalsRESPIRATORY, CIRCULATORY, EXCRETORY• diffusion through body wall and body• Some with excretory canal

NERVOUS• Cephalization groups of nerve cells at head

forming ganglia• Chemical sensory cells along bodyMUSCULAR• Only longitudinal muscles along length of bodyREPRODUCTION• Sexual through internal fertilization• Most species with separate sex (male, female)• Some hermaphroditic (with both m & f organs)Triplobasts – endoderm, ectoderm and mesoderm.

Why develop a complete digestive system?

• You can ingest new food while you are still digesting old food.

• More efficient capture of energy.

Pseudo-coelemate• What's the word Pseudo mean?• Pseudo Science?• False• Nematodes have a body cavity but it is not created from the

splitting of the mesoderm.

Effects on Humans• River Blindness (Onchoceriasis)- Cause by parasitic roundworms spread by

black flies in water• Elephantiasis-Filarial worms live in blood and lymph vessels (transfer by biting insects like via mosquito)• Trichinella worms -Uncooked pork,Cause Trichinosis

Videos• River Blindness:

..\..\..\Lesson Videos\Biology 11\Later Invertebrates\River Blindness - Tanzania.flv

• Elephantiasis:..\..\..\Lesson Videos\Biology 11\Later Invertebrates\Elephantiasis Afflicts 120 Million in Africa, Asia.flv

Assignment: draw the life cycle of either parasitic worm. Show in the human part of the life cycle which areas of a person are being affected. Gallery walk.

Can you remember the main differences between:

Platyhelminthes

• Hermaphroditic• Only one opening (mouth)

• Flat

Nematodes

• Mostly male or female• Fully developed digestive

tract• Round (due to the

pseudocoelom)

In Groups come up with a one or two sentence description of each.

Create a Chart

• Draw a large chart differences Platyhelminthes and Nematoda.