Phylum Platyhelminthes (Flat- worms)

General Information Bilaterally symmetrical  Left and right half mirror each other Dorsal-top surface of animal Ventral- bottom surface of animal Anterior- front end of the animal Posterior-backend of the animal

Ventral Anterior Posterior Dorsal

Info Cephalization  developed a definite head region. What does having a head enable you to do?? Move faster, sense better Organs  a collection of different tissues that work together to perform a particular function

Phylum Platyhelminthes (Flat- worms) Bilaterally symmetrical Lack respiratory and circulatory systems Solid body-no body cavity (acoelomate) The lack of a cavity also constrains flatworms to be flat; they must respire by diffusion no cell can be too far from the outside, making a flattened shape necessary.

Cont… Have organs –EX: eyespots One way gut- food in and waste out from the same place (YUCK!) First organism to develop cephalization Eyespots

Three Classes. Turbellaria  Most free-living marine One- freshwater-Planaria Eyespots to detect light- ocelli Can regenerate Hermaphrodite Water continuously enters body by osmosis so water needs to be removed-flame cells beat cilia and remove excess water.

Turbellaria - Planaria Have a pharynx (tube that extends from the gut) which functions as a mouth The planarian is non-parasitic, and eats decaying meat. Have auricles (sense lobes) on the side of the head Have a simple nervous system that includes a 'brain' Exhibit the remarkable ability to regenerate their lost body parts.

Trematoda 2. Trematoda  Parasitic have complex life cycles specialized for parasitism in animal tissues Sucking mouth-part Tegument  outer layer of skin that is undigestable Called flukes Endoparasitic- live inside host Ectoparasitic- live on the outside of host

Parasite Adaptations 1. Reduced sense organs 2. Reduced locomotion 3. Reduced ability to maintain homeostasis 4. Elaborate life cycles 5. Special organs of attachment 6. High Reproductive Capability Usually with multiple hosts

Schitosoma EX: Schistosoma (blood fluke)  lives in blood vessel of infected host and causes bleeding of the liver-infestation occurs in the tropics- larvae bore into skin without host knowing it- will kill 800,000 people this year-can ingest with fish Reservoir host is a snail. In Dayton we have Avian blood flukes (birds) – swimmers itch

Cestoda 3. Cestoda  Parasitic (endoparasite) Lack mouth Lack digestive track Many are segmented and each segment is called a proglottid Each proglottid has a male and female organs capable of reproduction (lots of babies)

Tapeworms-attach to intestine wall-absorb food through their skin-grow by producing a string of rectangular body sections called proglottids-can be 40 ft long-Proglottid is full of eggs-break off and release eggs everywhere Can infect humans-if you eat meat that isn’t cooked well-

Tapeworm The tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. When the segment drops off, it is basically just a sac of tapeworm eggs. The sac is passed in the hosts stool or rear end and enters the world

Homework 1. A dog is rolling on its back, wagging its tail. What kind of symmetry does the dog have? Name the body surface of the dog that is rolling on the ground, and identify the end with the wagging tail? 2. Why do you think it an advantage to have multiple hosts? 3. Why is it important to properly cook beef?

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