Chapter 34 Section 1 Phylum 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?