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Chapter 34
Section 1Phylum Platyhelminthes
Structure & Function• Bilateral symmetry• Ectoderm, endoderm, mesoderm• No hollow body cavity- acoelomate• Gastrovascular cavity like cnidarians-
single opening• Sensory organs located at the anterior
end of body- cephalization
Structure & Function • Four classes:• Turbellaria- free-living, non-parasitic• Trematoda- parasitic• Monogenea- parasitic• Cestoda- parasitic
Class Turbellaria• Planarians• Arrow-shaped head• Most live in the ocean, some in
freshwater• Glide through the water using mucus
and propelled by cilia
Class Turbellaria• Digestion & Excretion• Scavengers- feed on dead and decaying
matter• Food is ingested by pharynx- runs
through middle of body• Use flame cells to get rid of extra water
since they are constantly taking in water.
Class Turbellaria• Neural control• More complex than cnidarians• Cerebral ganglia- simple brain
(cluster of nerve cells at anterior end)• Eyespots- organism can sense light
with these structures
Class Turbellaria• Reproduction• Hermaphrodites • Sexual reproduction- mate with other
planarians• Asexual reproduction-
regeneration/fission- body splits into two pieces
Classes Trematoda & Monogenea
• Parasitic flukes- leaf-shaped flatworms that parasitize many kinds of animals, including humans• Tremadoes- wide range of hosts-
blood, intestines, lungs, liver, or organs• Monogeneans- ecto-parasites- fish
Classes Trematoda & Monogenea
• Structure• Anterior & ventral sucker• No eye spots• External surface covering- tegument-
helps protect parasite when inside host
Classes Trematoda & Monogenea
• Reproduction & Life Cycle• Hermaphroditic • Primary host- parasite gets
nourishment from• Intermediate host- host from which
the larvae derive their nourishment
Classes Trematoda & Monogenea
• Reproduction & Life Cycle• Schistosomiasis- affects 200 million
people, mostly from Asia, Africa, & South America
Class Cestoda• Tapeworms• Live in intestines of vertebrates• Found in raw or undercooked food
containing eggs or larvae• Causes: weight loss, digestive
problems, lack of energy, etc
Class Cestoda• Structure• Tegument to protect from host
defence• Scolex- knob-shaped organ found at
anterior end of tapeworm- attaches worm to host
Class Cestoda• Structure• Proglottids- long series of body
sections, as it grows it adds proglottids• Can grow up to 33 feet in some cases!• Lack eyespots, sensitive structure, no
mouth, no digestion
Class Cestoda• Reproduction & life Cycle• Hermaphrodites• Cysts- dormant larva with protective
covering
REVIEW!!!• Name the four classes and an example of
each from the Phylum Platyhelminthes.• What kind of nervous system does the
Class Turbellaria have?• Where do tapeworms originate from?
What Class can we find them in?