Transcript Presentation

Phylum
Platyhelminthes
General Characterisitics
• Bilateral symmetry
• Acoelomate
• Triploblastic
• Dorsoventrally Flattened
• Un-segmented bodies
• Cephalization (has a head)
Characteristics Cont.
• 20,000 species
• Actual organ systems present
–Nervous, Digestive, Excretory
Taxonomy
• 3 Classes
–Class Turbellaria
–Class Trematoda
–Class Cestoidea
Class Turbellaria
Planarians
Free-living bottom-dwellers in
aquatic environments
few terrestrial species in the tropics
3,000+ species
Vary widely in color, size, and shape
Terrestrial ones can be up to 60cm
Body Description
3 Layers
Ectoderm
Mesoderm
Endoderm
Acoelomate- have a solid mass of
mesoderm cells between the ectoand endo- derms
Acoelomate Design
Locomotion
As bottom dwellers the flat
worms glide over the substrate
(ground)
Use cilia and muscular
contractions
Lay down a sheet of mucous as
they travel (like slugs)
Body Systems
Digestive- can be simple or complex
Pharynx: muscular ingestion organ
Some digestion takes place outside
the body
Enzymes secreted on food
particles; helps to break them
down so the pharynx can swallow
them easier.
Digestive System
Body System Con’t
Respiratory- have none
gases are exchanged over the
epidermis
Circulatory
Protonephredia: fine networks of
tubes that run the length of the body
and collect waste
Flame cells: bulb-like structures that
force waste out of the body through
openings called nephridiopores.
Excretory System
• Nervous: detecting and responding
to environment
–Simple: nerve net w/ Statocystssense gravity
–Complex: nerve net and two main
nerve cords with ladder like
connections between
• Auricles: chemoreception
• Ocelli: eyespots; detect light
Nervous System
• Reproductive:
–Most hermaphrodites
–Exhibit both sexual and asexual
• Asexual- transverse fission
• Sexual- mutual sperm transfer
Planarian Body
Systems
Class Trematoda
• Parasitic flatworms (called flukes)
• 1mm to 6cm in size
• Most infect internal organs – can
be blood or virtually any
other organ
Primary host = the
host in which a
parasite reproduces
sexually
Intermediate host =
the host in which
asexual reproduction
occurs
Fish Flukes
• 30 million people infected in Asia
• Caused by eating raw or
improperly cooked fish
• Resides in liver bile ducts
• Causes fever, weight loss, joint
aches, inflammation, hives,
weakness, diarrhea, and an
enlarged liver.
Chinese Liver Fluke
More Flukes
• Liver Flukes
–Live in the liver bile ducts of
sheep and humans
–Host infected by eating aquatic
vegetation (watercress)
• Schistosomes: blood flukes
–Millions infected worldwide
–Causes rash, fever, chills,
inflammation, liver and spleen
enlargement.
Schistosoma mansoni - multiple host:
Primary host = human
Intermediate host = snail
Causes Schistosomiasis -in humans; decays
lungs liver, spleen, or intestines, occurs in
tropical areas with poor sanitation/sewage.
Blood Fluke
Class Cestoidea
• Tapeworms
• 3,500 species
• All are endo-parasites of
vertebrates
Lack a mouth and digestive tract
Body consists of 3 main parts
scolex: hold fast structure
Strobila: the neck region
Proglottids: reproductive sacs
that make up 90 percent of the
body
Each mature proglottid is a
hermaphrodite
Testes produce sperm, fertilize the
eggs to produce a zygote
Zygotes are
passed out
through the
feces.
Sometimes, a dormant, protective cyst is
formed in the intermediate host muscles
****This is why you should never eat
incompletely cooked meat.
Tapeworm Life cycle
Tapeworm Life Cycle