Transcript Unit 3 - Warren County Schools

(flat + worm)
Over 20,000 species.
: Aquatic free-living OR parasitic
Flatworms-Platyhelminthes
Least complex worm
 No body cavity (acoelomate)
 No respiratory system
 No circulatory system

◦ All cells close to environment
:
(three germ layers)
1.Ectoderm-Nervous, sensory, skin
2.Mesoderm-Connective tissue, reproductive,
excretory, muscle.
3.Endoderm- Gut/respiratory lining, digestive.
Regeneration is the ability to
“re-grow” lost body parts.
This is possible because the
organism has the ability to
form a blastema, which is an
accumulation of
undifferentiated cells, at the
site of the wound called
(adult stem cells)
These undifferentiated cells
will eventually differentiate
into the missing parts.
Flatworms

Three Classes
◦ Turbellerians (Planarian)
◦ Cestoda (Tapeworms)
◦ Trematoda (Flukes)
(commotion + like)
Turbulence of cilia
gives name
•Free living
•Freshwater or
marine
•Bottom dwelling
•Osmosis Problem –
flame cells pump out
water (remember
contractile vacuole)
•Over 3000 species
Turbellarians
Symmetry –Bilateral
 Structure
◦ shovel head
◦ flat body

rodlike cells that form protective mucus layer
: secretes chemical that sticks animal to substrate
A) Nervous system
B) Reproductive system
C) Digestive system
NERVOUS SYSTEM

Mass of nerve cells [ganglia] form
a simple brain

Ladder-like arrangement
throughout body

Head sensitive to touch, smell, and
taste

Two eyespots sensitive to light
REPRODUCTION

Reproduction
 Asexual
 If cut into pieces – each piece will
grow into new organisms
 Split themselves apart
 Sexual
 Produce both male and female sex
cells (hermaphodidic)
 Cannot fertilize itself
 Lay eggs
When conditions are favorable, the organism
will attach its tail-end to the ground and pull
forward with its head-end until it tears itself in
half. Each end will then regenerate its missing
half.
This is a form of asexual reproduction called
. The two “new” planaria are clones of
each other, both possessing identical genes.
COOL!
Planaria Regeneration
An injury divided
the head of this
planarian in half.
The two halves
regenerated their
lost parts.
Eventually, the
planarian will split
lengthwise into two
new planarians.
Turbellaria use their pharynx on ventral side to
capture food.
One way digestive system so waste exits pharynx
too .
Feed on small inverts.
Also scavengers, and
herbivores.
Partial external digestion
so food is small enough
to ingest.
Digestion
Excretion
The Monsters Inside Me
(perforated + form)
Common name
- Parasitic to vertebrates
: Most of life cycle spent in host organism
(liver fluke)
Class Trematoda
Parasitic flukes
a) Liver flukes
b) Schistomomes / intestinal
flukes that suck blood
c) use snails as an intermediate host
sucker
FLUKE – flat/parasitic
Monoecious / hermaphroditic
ovary
uterus
Class Trematoda
testis
Feed on the host’s cells.
: exterior layer of fluke that aids in
transport of nutrients & protects from host
organisms digestive enzymes.
suckers
SEM image
Intestinal
Schistosomiasis
16 yr. Old boy
Abdomen accumulates fluida body immune response to
eggs embedded in tissues
Definitive host
Schistosomiasis
Intermediate host
(girdle + form)
: Vertebrate digestive
system
TAPEWORM
: Cestodea absorb
all of their nutrients from the
digestive tract of it’s host.
(no mouth)
Tapeworm showing proglottids
Mature proglottids
:
Cestoidea can grow from 1mm to 30m in length. (~100ft)
They consist of two main body parts.
1)
(head) -Attachment structure
Tapeworm scolex (head )
light microscope
suckers
Immature proglottids)
hooks
Tapeworm scolex and hooks
SEM image
I love you
2)
(reproductive body)
-Reproduction & Nutrient absorption
: each segment of the worm, containing a complete
reproductive structure
Dog eats infected flea
Worm grows
in dog
Flea larva eats tapeworm eggs.
Tapeworm larvae develop inside flea
Proglottids with
eggs leave in wastes
(Wheel + to Bear)
: Most freshwater. About 10% marine
Solitary, free-swimming
Name is derived from the Corona (head)
Rotifer size: 0.1-3.0 mm
~1000 cells large
:
Triploblastic
Bilateral
Pseudoceolomate
Organisms that have a fixed number
of cells when they reach maturity, the exact
number being constant for any one species.
Approx 1000 in Rotifers, depending on the species.
Complete digestive tract
Excretion with Flame Cells
Feed on SOM or small microorganisms
: Jawlike organ that grinds food
Ciliated digestive tract
helps move food through
Summer eggs (thin shelled)
Winter eggs (thick shelled)
Rotifer video 2:30
Rotifer 1:30
Rotifer feeding
(thread)
Numbers: ~15,000 -- 500,000 species
Described
Estimated
Parasitic to plants or animals
Some free living
:
Triploblastic
Bilateral
Pseudocoelomate
Size:
Microscopic -- 2-5m long
Round in cross section
Long slender & tapered at both ends
: Feed on ANY type of organic matter.
(Carnivorous, herbivorous, omnivorous, saprobes, parasitic)
Cuticle provides protection against digestion by host.
Separate sexes.
(male & Female)
: Each sex has
different anatomical
characteristics
• Intestinal roundworm, infecting small intestine of humans
and other large mammals.
• Eggs exit with feces.
• Host must eat eggs to become contaminated and continue life cycle.
Egg
produced
by adult
exits in
host in
feces
Adult
stage in
host
intestine.
Host
ingests
eggs
Migrate to
trachea,
carried to
stomach
Hatch in
host
intestine
Molt in
lungs
Migrate to
lungs as
larva
(pinworm)
• Most common roundworm in US
• Lives in host(human) large intestine
• Eggs may be inhaled through infected dust
Eggs ingested
by host
Host gets
eggs on
fingers
Adult
migrates to
perianal
region to lay
eggs at night
Organism
matures in
host large
intestine
Adult lives in
host large
intestine
(hookworm)
• Southern US
• Feed on blood & tissue fluids
• Lays up to 10,000 eggs daily
Develop
into larva in
the
mud/soil
Eggs hatch
in feces
Eggs
produced
Penetrate
host skin
through
toes
Adult stage
in small
intestine
Swallowed
by host
Matures
and
migrates
to trachea
Enters
circulatory
system
Migrates
to lungs