Phylum Platyhelminthes

Michael Xu & Patricia ChengPeriod 6

General Characteristics Mostly parasitic They are acoelomates Soft and ciliated epidermis, or covered with

cuticle and with external suckers or hooks – used to attach to host

About 20,000 species found in marine and freshwater

Free living flat worms rely on camouflage. Flatworm can be microscopic or many feet

long and is generally very thin

Classes

http://www.thaigoodview.com/library/contest2551/science04/119/kingdon_animalia/images/turbellaria4.jpg

Turbellaria [free living flatworms]

Monogenea[flukes]

http://www.nhc.ed.ac.uk/images/collections/invertebrates/parasitic/LgMonogenea.jpg

Classes ContinuedTrematoda[flukes]

Cestoda[tapeworms]

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/01fluke.gif

http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20102/Bio%20102%20lectures/Animal%20Diversity/lower%20invertebrates/tapeworm1.jpg

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Form & Function

Feeding

Respiration

Excretion

Circulation

Response

Movement

Body Plan

Reproduction

End

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Body Plan Bilateral Symmetry Body has 3 layers of tissues with organs and

organelles (triploblastic) No internal cavity Has a blind gut, mouth but no anus Dorsoventrally flattened (hence, flatworms) Cephalization, a specialization of the anterior

end of the animal, can be seen in the clustering of sensory structures and clumps of nerves in the head region.

The mesoderm gives rise to muscles, various organ systems, and the parenchyma

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Feeding Usually carnivorous,

eating a wide range of living and dead organisms

Some species feed on algae

Mostly they feed on animals and other smaller life forms

Turbellarians have a muscular pharynx to up food.

Parasitic classes rely on the host for digestion.

http://infusion.allconet.org/webquest/PhylumPlatyhelminthes.html

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Respiration Respiration occurs through diffusion, on the cellular level Being flat helps the diffusion A flatworm takes in oxygen, but has no formal

respiratory system.

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http://www.earthlife.net/inverts/platyhelminthes.html

Circulation Circulation occurs

through diffusion. No special organs for

circulation, gut is only body cavity

The gut is often highly branched to allow for more effective transportation and diffusion of food to all parts of the body

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http://www.pbs.org/kcet/shapeoflife/animals/platyhelminthes.html

Excretion Incomplete digestive

system, no anus, usually much branched

Excretory system consists of many flame cells connected to excretory ducts

A flatworm has a combination digestive/excretory system.

A flatworm gets rid of wastes through the same opening it takes in food.

Protonephridial excretory organs replace anus

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http://www.ucmp.berkeley.edu/platyhelminthes/platyhelminthes.html

Response A flatworm has a very simple nervous system with two

nerve cords running down either side. It has two simple brains called ganglia, which are

simple bundles of nerves. It has two eyespots (ocelli) that help it sense light. Some platyhelminthes have chemoreceptors, balance

receptors, and receptors for water movement

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http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm

Movement Some groups, like

turbellians, use cilia on the epidermis for locomotion on slime trails

Parasitic worms rely on the hosts circulatory system for transportation

Some species have longitudinal, circular, and oblique layers of muscle under the epidermis which help with movement

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http://www.discoverlife.org/20/q?search=Platyhelminthes

Reproduction Mostly sexual

reproduction, as hermaphrodites

Reproductive system of each sex with gonads, ducts and accessory organs

Fertilization occurs internally

Lays strings of microscopic eggs each enclosed with several yolk cell in a shell

Development is either direct or with one or more larval stages

Asexual reproduction occurs through fragmentation or fission.

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http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm

BibliographyTEXT "The Flatworms and Tapeworms (Phylum Platyhelminthes)." The Earth Life Web. Web. 20 Apr.

2010. <http://www.earthlife.net/inverts/platyhelminthes.html>. "Introduction to the Platyhelminthes." UCMP - University of California Museum of Paleontology.

Web. 20 Apr. 2010. <http://www.ucmp.berkeley.edu/platyhelminthes/platyhelminthes.html>. "Platyhelminthes." W. Fielding Rubel School of Business: Bellarmine University. Web. 20 Apr.

2010. <http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm>. Platyhelminthes." Oracle ThinkQuest Library. Web. 20 Apr. 2010.

<http://library.thinkquest.org/26153/marine/platyhel.htm>. "M31.htm." Meer Home Page. Web. 20 Apr. 2010. <http://www.meer.org/M31.htm>. "The Shape of Life . Platyhelminthes." PBS. Web. 20 Apr. 2010.

<http://www.pbs.org/kcet/shapeoflife/animals/platyhelminthes.html>. "Flatworm." Monroe County Women's Disability Network. Web. 20 Apr. 2010.

<http://www.mcwdn.org/Animals/Flatworm.html>. "Phylum Platyhelminthes." Infusion. Web. 20 Apr. 2010.

<http://infusion.allconet.org/webquest/PhylumPlatyhelminthes.html>. "Animals - Phylum Platyhelminthes." Oracle ThinkQuest Library. Web. 20 Apr. 2010.

<http://library.thinkquest.org/28751/review/animals/3.html>.PICTURE "Platyhelminthes - Flatworms, Tapeworms, Flukes." Discover Life. Web. 20 Apr. 2010.

<http://www.discoverlife.org/20/q?search=Platyhelminthes>. สาระ ความร� ข่�าวสาร ความบั นเทิ�ง ข่องชาวม ธยมศึ�กษา และประถมศึ�กษา : Knowledge for Thai Student |

ThaiGoodView.com. Web. 20 Apr. 2010. <http://www.thaigoodview.com>. Natural History Collections: Home. Web. 20 Apr. 2010. <http://www.nhc.ed.ac.uk>. Estrella Mountain Community College. Web. 20 Apr. 2010. <http://www.emc.maricopa.edu>. Clinton Community College. Web. 20 Apr. 2010. <http://faculty.clintoncc.suny.edu>.