Video
• ..\..\..\Lesson Videos\Biology 11\Gold Mines
Unearth Worms From Hell.flv
Battle of The Worms
The Combatants
Platyhelminthes
Nematoda
FLAT
ROUND
Annelida
SEGMENTED
What can we say about the appearance of the
various worms?
Notice where they each are.
Are Platyhelminthes the first bilateral
animal?
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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 phyla
First up: Platyhelminthes
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OVERVIEW
Un-segmented body plan
DIFFUSION
Flat
Carnivores or Scavengers MACHINES!
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
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=w0QzSYQ
GsnA
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
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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)
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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
Invertebrates\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.
..\..\..\Lesson Videos\Biology 11\Later
Invertebrates\Planarian Regeneration Part 1.mov.flv
http://www.youtube.com/watch?v=J9EuFuJF9
N0&feature=related
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 parasites
DIGESTION
• 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
animals
RESPIRATORY, 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 body
MUSCULAR
• Only longitudinal muscles along length of body
REPRODUCTION
• 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
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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
Nematodes
In Groups come up with a one or two sentence description of each.
• Hermaphroditic
• Only one opening (mouth)
• Flat
• Mostly male or female
• Fully developed digestive
tract
• Round (due to the
pseudocoelom)
Create a Chart
• Draw a large chart differences Platyhelminthes
and Nematoda.