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Phylum Platyhelminthes Phylum Nematoda

This overview delves into the characteristics of two essential phyla: Platyhelminthes (flatworms) and Nematoda (roundworms). Platyhelminthes display bilateral symmetry, possess three cell layers, and exhibit diverse life strategies as either free-living or parasitic organisms. Nematoda showcases unique features such as a pseudocoelom and a one-way digestive system, allowing them to thrive in various environments. Both phyla have significant ecological roles, contributing positively to ecosystems while some species, like Ascaris and Trichinella, pose health risks.

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Phylum Platyhelminthes Phylum Nematoda

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  1. Chapter 36 Phylum PlatyhelminthesPhylum Nematoda gecko.gc.maricopa.edu www.ncbi.nlm.nih.gov

  2. Phylum Platyhelminthes gecko.gc.maricopa.edu • Common Name: Flat worms • Examples: Tapeworm, Fluke, Planaria • Characteristics: • Bilateral Symmetry • 3 cell layers • Organs • Free-living or parasites • Flattened body • Nutrition: Scavengers, Parasites or Hunters members.aol.com

  3. www.biosci.ohio-state.edu Tapeworm www.abdn.ac.uk Scolex www.ndpteachers.org

  4. Planaria www.luc.edu

  5. Systems • Digestive: Simple - one opening, called the mouth, highly branched intestine allows nutrients to diffuse into individual body cells. • Parasites like the tapeworm absorb nutrients through their tegument or cuticle. • Nervous: Simple brain and nervous system. Planaria have eyespots to detect light.

  6. Systems • Reproductive: Asexual – they can stretch in two and have remarkable regenerative abilities. Sexual – hermaphrodites with cross-fertilization. • Excretory: Most use simple diffusion, but planaria use flame cells to excrete liquid waste and undigested food exits the mouth. • Respiration: Diffusion of gasses through skin.

  7. I don’t care who you are – That’s just cool. http://classes.design.ucla.edu/Spring05/152BC/projects/saito/ex3/planaria.jpg

  8. Positive Clean up detrius (dead organic matter) Negative Parasites Ecological Impact Schistosoma evolution.berkeley.edu

  9. Phylum Nematoda • Common Name: Roundworms • Examples: Ascaris, pinworm, hookworm, Trichinella, Filarial worms, Tubatrix www.organicnutrition.co.uk www.emc.maricopa.edu www.rlc.dcccd.edu www.organicnutrition.co.uk

  10. Phylum Nematoda • Characteristics • Bilateral Symmetry • Pseudocoelom • Parasitic or free-living in soil or water • First with a one-way digestive system • Size ranges from microscopic to 4 feet! • Nutrition: Herbivore, carnivore or scavenger. Free-living burrow through soil, parasitic often absorb nutrients through tegument/cuticle.

  11. Pseudocoelom members.aol.com Muscles Nerve Cord Pseudocoelom Intestine Ovaries Excretory Canal Uterus

  12. Systems • Digestive: Complete. Mouth and anus present • Nervous: Simple brain and nervous system • Reproductive: Sexual – separate sexes • Excretory: Simple – pore at anterior end for liquid waste. Solid waste exits through anus. • Support: Pseudocoelom • Respiration: Gasses diffuse across skin, aided by pseudocoelom. • Circulation: Fluid in pseudocoelom distributes nutrients to body cells.

  13. Positive Hookworm anti-clotting factor has been isolated, prevents clotting in arteries of cardiac disease patients Kill organisms in soil that harm plants, even insect larvae Organify and aerate soil, good for drainage and irrigation Used in the study of developmental biology Negative Ascaris, trichinella, pin worms, etc. cause disease Economic damage to crops Ecological Impact www.sghms.ac.uk

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