Phylum Platyhelminthes
Platyhelminthes:
1.
2.
3.
4.
“Flat”worm
One body
opening
Very simple
Nervous &
Muscular Systems
May be Parasitic
or Free living
Planarian: (Class Turbellaria)
1. Free-living flatworm with
2. Bilateral Symmetry
3. Lives in freshwater
4. Found under leaves & rocks
5. Feeds on dead or slow moving
organisms
6. Reproduction:
a. Sexually: Hermaphrodites = Male & Female Parts
b. Asexually: Fission = can regenerate body parts
7. Nervous & Sensory System
a. Brain-like Ganglion located in anterior region
b. Nerve cord to carry impulses
c. Eyespots: sense
light & dark
d. Sensory pits line
sides of head to
aid in movement
e. Cilia line body & aid in
movement
f. Flame cells remove excess
water & nitrogenous wastes
7. Digestion: Food enters mouth &
solid wastes exit mouth
a. Mouth: located in center of
ventral side
b. Pharynx: tube-like struture
which extends from mouth
during feeding-acts like a
straw sucking up food &
carrying it to the body
Figure 27–3 Page
The Anatomy of a Flatworm
Freshwater flatworms have
simple ganglia and nerve
cords that run the length of
the body. The excretory
system consists of a
network of tubules
connected to flame cells
that remove excess water
and cell wastes.
Head
Eyespot
Flatworms use a
pharynx to suck food
into the gastrovascular
cavity. Digested food
diffuses from the
cavity into other cells
Mouth
of the body. Eyespots
in some
species detect light.
Pharynx
Flame cell
Most flatworms are
hermaphrodites,
having male
reproductive organs
(testes) and female
reproductive organs
(ovaries) in the same
organism.
Tapeworm (Class Cestoda)
1. Parasitic Flatworm
2. Lives in the Intestines of Vertebrates
3. Can grow up to 10 meters in length!
4. Reproduction: Hermaphrodites
5. Flattened body is made up of individual
segments called: Proglottid
a. Each proglottid is detachable
b. Each proglottid may contain up to
100,000 eggs
c. Fall off when full
d. Released with wastes
6. Head Region: Scolex
a. Surrounded by hooks & suckers to aid
in attachment to intestine
b. Smallest section of worm
c. Proglottids grow out from scolex
7. Life cycle:
a. Eggs hatch in intestines of
Intermediate Host (pig)
b. Young worms burrow into pig
muscle
c. Secondary Host (man) eats
undercooked/raw meat
contaminated w/ worm larvae cysts
d. Larvae hatch & mature in intestines,
must live in intestines since they don’t
have them
e. Attach to intestines and soak up
digested food of host
f. May enter bloodstream & infect other
tissues w/ cysts
Flukes(Class Trematoda)
1. Parasitic Flatworm
2. Lives in Digestive System or Liver
3. Feeds on cells, blood, & body fluids
4. Blood flukes:
a. Eggs are released in water from
wastes of infected host
b. Hatch into larvae
c. Larvae enter snail where they
develop & reproduce
d. Enter water again & bore into
skin of new host
e. From blood, they bore into intestines
where they attach & feed on blood
5. Liver flukes:
a. Lodge in liver ducts of host
b. Block liver ducts which can cause liver
damage or failure
Quiz #2
Flatworms
IN
1. Planarians have ___ symmetry.
a. bilateral b. radial c. assymetrical
d. symmetry
2. Flatworms reproduce sexually, they are hermaphrodites,
what does this mean?
A. produce only sperm
C. produce only eggs
B. produce egg & sperm
D. none
3. A tapeworms body is made of individual segments called
__
A. segments B. flame cells C. scolex D. proglottids
4. The difference between planarians and tapeworms?
a. planarians are parasites, tapeworms are freeliving
b. tapeworms are parasites, planarians are freeliving
c. both are parasites d. all the above
5. The function of ___ is to remove excess water & waste
A. pharynx
B. flame cells
C. fission
D. cysts