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Phylum Platyhelminthes

Phylum Platyhelminthes. Flatworms. Introduction. # of species: 13,000 Size: wide range, from very small to very long/big 2 type of bodies: 1) Slender and leaflike 2) Long and ribbonlike 2 types of symbiotic relationships 1. Free living 2. Parasites

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Phylum Platyhelminthes

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  1. Phylum Platyhelminthes Flatworms

  2. Introduction • # of species: 13,000 • Size: wide range, from very small to very long/big • 2 type of bodies: • 1) Slender and leaflike • 2) Long and ribbonlike • 2 types of symbiotic relationships • 1. Free living • 2. Parasites • Adaptations: Organs that help them stick to host

  3. Acoelomate • Lack a coelom or pseudocoelom

  4. Characteristics • Triploblastic – Organisms with three germ layers • 1. Endoderm • Def – digestive system comes from this • 2. Ectoderm • Def – nervous system comes from this • 3. Mesoderm • Def – Muscular system and reproductive organs comes from this

  5. Characteristics • Symmetry: Bilateral • Description: True anterior and posterior end • Body: Flattened • Internal area: One space (with all organs contained within it) • Head region: Cephalization present • This is when animals have a well defined head region

  6. Characteristics • Excretory system/Osmoregulatory • Main cell type: Flame cell • Description: • Bulb shaped • Function: Excretion of wastes • Consist of: Large amount of cilia (hair-like appendages), long canals that run the length of the body • Location: Along the length of body

  7. Flame Cell

  8. Characteristics • Digestive system: Incomplete (mouth, pharnyx and intestine) • Nervous system • Description: pair of ganglia (concentrations of nervous tissue/cells) • Longitudinal nerve cords • Bilobed brain • Ocelli - light sensitive eyespot • Neurons – sensory, motor and association types

  9. Muscular system • Description: layers of circular, diagonal and longitudinal fibers beneath the epidermis • Epidermis • Cellular or syncytial (nuclei not separated by cell membrane) • Some are ciliated • Often described as “tegument” rather than a true epidermis • Unsure if this arrangement relates to parasitism

  10. Characteristics • Respiratory system • NO real respiratory organs • Circulatory system • NO real circulatory organs • Skeletal system • NO skeletal system

  11. Characteristics • Reproductive System • Most are monoecious • Def: have BOTH male/female reproductive parts in the SAME individual • Practice cross-fertilization • Asexual reproduction by fission • Regeneration of missing parts

  12. Reproductive System • Havecomplex reproductive systems - well developed gonads and accessory reproductive organs

  13. Classification • Kingdom Animalia • Phylum Platyhelminthes • Class Turbellaria • Ex. Planarians • Most are free-living (do not rely on host to live) • Mostly marine/salt-water • Body: soft, flattened • carnivorous

  14. Class TurbellariaProstheceraeus

  15. Class TurbellariaDugesia(Ex: Planaria)

  16. Classification • Kingdom Animalia • Phylum Platyhelminthes • Class Trematoda • Ex. Lung, liver and blood flukes • Symbiotic relationship: parasitic (live in host and harm the host) • Body: soft, flattened • Oral and ventral suckers with no hooks • Cause Schistosomiasis • Description: world’s second most common infectious disease, causes severe diarrhea

  17. Liver Fluke Life Cycle

  18. Class TrematodaLiver and Blood Flukes

  19. Classification • Kingdom Animalia • Phylum Platyhelminthes • Class Cestoda • Ex. Ribbon worms, tapeworms • Symbiotic relationship: parasites OR free-living • Body: flat, ribbon-like segmented body • Digestion: No digestive tract so dependent on host’s digestion • Tegument covered in microthrix (similar to microvilli which increases surface area)

  20. Scolex • most specialized structure • Organ of attachment

  21. Class CestodaRibbon Worms

  22. Class CestodaTape Worms

  23. Phylum Nematoda(Nemata) Roundworms

  24. Origin and Diversity • Location in world: Live everywhere! (oceans, freshwater, soil, polar regions, tropical zones, mountains) • Simplest organism to have complete digestive tract ( mouthanus) • # of species: hundreds of thousands • Symbiotic relationship: free-living and parasitic • Ex: Pinworms • Pinworms: can affect crops, domestic animals and humans, infect 30% of all US children

  25. Characteristics • Symmetry: Bilateral • Unsegmented • Germ layers: Triploblastic (three layers) • Adults have a pseudocoelom • Def: closed fluid-filled space acting as a hydrostatic skeleton • Description: tube-within-a-tube • Function: aids in circulation and dispersal of nutrients and movement of organism • Body wall: thickened cuticle • Description: Hardened protective covering • Muscle layers:mostly longitudinal

  26. Characteristics • Digestive system • Complete digestive system • “Tube within a tube” arrangement • Food comes in through mouth, leaves through anus • Circulatory system • NO true circulatory system/organs • Hydrostatic skeleton – aids in moving materials • Respiratory system • NO true respiratory system/organs

  27. Characteristics • Excretory System • Contain a cloaca • A cavity that receives excretory and reproductive systems products Nervous System • Cerebral ganglia (nerve ring) • Nerve ring is connected anterior and posterior nerves • Contain many sensory organs (cilia, bristles, eyespots) • Reproductive System • Contain gonads • Sexes usually separate • Males are smaller than females

  28. Classification • Kingdom Animalia • Phylum Nematoda • Examples: Pinworm, filarial worms, Ascaris, hookworms • Can be parasitic • Cause: Elephantiasis, inflammation of limbs, death, hearing loss, intestinal irritation/diarrhea

  29. Trichinellaspiralis Ingestion of infected muscle

  30. Trichuristrichiura“whipworm”

  31. Ascarislumbricoides Intestinal Roundworm

  32. Dirofilariaimmitis

  33. Dracunculusmedinensis

  34. Phylum Mollusca Mollusks

  35. Origin and Diversity • # of species: 100,000 • Classified by shell type, foot structure and internal body organization • Mollusca, means “soft animal” • From the Latin word Mollis which means soft

  36. Characteristics • Development • Torsion – twisting of the body • Causes the mantle to rest over the head • Allows for body to face the incoming current (of water), so that they can stay attached to rock surface • Symmetry: Bilateral • Usually have definite head region • Bodies: Soft • Some have a protective shell (snail) • Others may have 2 shells (clams) OR internal shell (octopus)

  37. Characteristics • Mantle • Soft outer tissue layer • Contained on DORSAL body wall • Secretes a protective shell • Mantle Cavity • Forms between the mantle and other body tissues • Holds respiratory organs (gills OR lungs) • Muscular Foot • Used for locomotion

  38. Characteristics • Visceral Mass/ Coelom • Contains most of mollusk’s internal organs • Includes: heart, gonads, stomach, kidneys • Circulatory System • Open circulatory system • Blood flows freely over body tissues • Blood is enclosed in vessels in some places • Vessels are open ended • Heart has three chambers

  39. Characteristics • Digestive System • Digestive tract has two openings • Contains a rasping organ called radula • Anus empties into mantle • Respiratory System • Gas exchange may occur in gills, lungs, mantle or body surface • Reproductive System • Most have separate sexes • All reproduce sexually • Internal fertilization: Squid, some snails • External fertilization: Clams, oysters

  40. Characteristics • Nervous System • Some have simple system • Contain sensory organs • Touch, smell, taste, vision • Eyes are highly developed • Some contain ganglia: centralized nerve ring • Others have pairs of ganglia • Octopus have very complex nervous systems

  41. Characteristics • Movement • May slide (snail, slug) • Bury foot and use as a shovel (clams) • Expel water quickly (squid, octopus) • Sessile (don’t move) • Shell • Made of calcium carbonate • Fossilizes easily • Explains rich fossil record

  42. Classification • Kingdom Animalia • Phylum Mollusca • Class Polyplacophora • Marine organisms • Found on hard sea bottoms/rocky coasts • Can withstand strong waves • How? By attaching its strong “foot” to rocks • Breathe? Gills along the side of body • Eat? Use? Radula to scrape algae off rocks • Some are predatory (hunt others for food) • Other: Little use to humans (some can be eaten)

  43. Class Polyplacophora • Ex. Chitons

  44. Classification • Kingdom Animalia • Phylum Mollusca • Class Gastropoda • Ex. Snails, slugs • Body: Coiled in shape • Head: Well developed • Feeding: Use radula • # of species: • over 40,000

  45. Class Gastropoda

  46. Classification • Kingdom Animalia • Phylum Mollusca • Class Bivalvia • # of species: 15, 000 • Includes: Clams, oysters • # of shells: two (Bi = two) • Feeding: Filter feeders

  47. Class Bivalvia

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