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Flatworms, Roundworms, and Rotifers. Germ Layers Layers of cells that originate in the developing embryo and become specific structures Ectoderm - outer.

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Presentation on theme: "Flatworms, Roundworms, and Rotifers. Germ Layers Layers of cells that originate in the developing embryo and become specific structures Ectoderm - outer."— Presentation transcript:

1 Flatworms, Roundworms, and Rotifers

2 Germ Layers Layers of cells that originate in the developing embryo and become specific structures Ectoderm - outer Mesoderm - middle Endoderm - inner

3 Acoelomate Without a coelom 2 germ layers Ectoderm and endoderm Not separated by a cavity Least complex body plan Sponges and cnidarians Body Plans

4 3 Layer Acoelomate 3 germ layers Endoderm, mesoderm and ectoderm Not separated by a cavity Flatworms

5 Pseudocoelomate Pseudocoelom Cavity formed between mesoderm and endoderm Roundworms and rotifers

6 Coelomate Cavity developed within the mesoderm Most complex body plan Mollusks, annelids, arthropods, echinoderms, and chordates

7 Phylum Platyhelminthes - Flatworms 13,000 species Bilaterally symmetrical Cephalization 3 classes (Turbellaria, Trematoda, and Cestoda) Trematodes and cestodes parasitic Parasites live in or on other organisms (host)

8 Parasitic Flatworms Originated from free living Some organs modified for parasitism Lack mouths Well developed digestive system

9 Hooks or suckers Tegument- thick covering of cells Cuticle- nonliving layer secreted by epidermis

10 Class Turbellaria 3000 species Most marine Ex. Planaria (fresh water)

11 Planaria Anterior end spade shaped Posterior end tapered Body covered with cilia External anatomy

12 Movement Move by undulative motion or Laying down mucus layer and beating cilia

13 Digestion and Excretion Scavenger (carrion) Predator (small prey)

14 Digestion Muscular pharynx extended out of mouth Food sucked in Passed into intestines (branched) Nutrients absorbed through intestinal wall or phagocytosis Undigested food excreted through pharynx and mouth

15 Excretion Chemical wastes and excess water eliminated by network of ducts (pores and canals) Contains flame cells Flame cells enclose a tuft of beating cilia Cilia moves wastes into the ducts -> Excretory pores -> out

16 Nervous Control Organized and cephalized Sense light intensity and direction Two anterior eyespots (photosensitive cells) Touch, taste, and smell receptors

17 Two anterior ganglia (clusters of nerves) -> simple brain Two longitudinal nerves connected by transverse nerves Capable of simple "learning" Memory stored chemically

18 Reproduction Hermaphrodites Sexual reproduction Simultaneous fertilization Protective encapsulated eggs stick to rock Hatch 2-3 weeks

19 Asexual (summer) Attach to rock surface with posterior end Stretch until they tear into two Each half regenerates lost parts

20 Class Trematoda 6,000 species Parasitic - both endoparasites and ectoparasites Leaf shaped

21 Structure and Reproduction of Flukes Parasites 1 cm long (oval shaped) Unciliated tegument

22 2 sucker mouths (anterior and ventral) Cling to host Anterior sucker sucks in blood, cells and fluids of host

23 Nervous and Excretory System Turbellarian like Reproduction Complex reproductive life cycle Hermaphroditic Long coiled uterus (stores eggs (10,000+) Eggs released through genital pore -> larvae

24 Life Cycle Adults live in sheep liver and gall bladder where they mate and produce eggs Eggs enter intestines -> Eliminated with feces - > Eggs hatch in water ->

25 Larvae invade snail -> Multiply asexually -> Leave snail and form cysts -> Cysts dormant larvae with hard protective covering

26 Ingested by sheep -> Hatch in digestive tract -> Bore through intestines into blood -> Mature and reproduce in liver

27 Schistosomiasis Blood fluke - schistosoma Infects million people (asia, africa, and so. America) Around lakes and rivers Spread via irrigation ditches and reservoirs

28 Adults live in human bloodstream Eggs lodge in veins, lungs, intestines, bladder, and liver Block blood vessels Cause internal bleeding and tissue decay

29 Class Cestoda - Tapeworms 1,500 species Most parasitic (7 in humans) Adapted for parasitic life Tough outer tegument

30 Hooks and suckers Nervous system extends length of body Lack sense organs, mouth, and digestive tract

31 Absorb nutrients directly through heavily folded tegument Knoblike head with hooks and suckers (scolex) Grows by producing body segments (proglottids) Oldest proglottids at posterior Excretory system drains proglottids of waste Life cycle and reproduction

32 Proglottids contain both male and female reproductive organs Cross fertilization is typical between individuals or proglottids After fertilization - proglottids break off and are eliminated with feces

33 Beef tapeworm Cattle eat grass with proglottids and eggs Larvae hatch Bore through cow's intestine -> blood stream

34 Burrow into muscle tissue and form cysts Human eats beef (muscle) -> intestine Cysts wall dissolves and bladder worm released Develops into an adult beef tapeworm

35 Nematoda and Rotifera Pseudocoelom Lined on the inside by endoderm and outside by mesoderm Fluid filled Contains organs

36 Supports the body Provides hydrostatic pressure against which muscles can contract Serves as a storage area for wastes or eggs and sperm

37 Phylum Nematoda - Roundworms 10, ,000 (million) species Long slender bodies that taper at both ends Flexible protective cuticle

38 Digestive tract with two opening (1 way) Anterior mouth Posterior anus Sexes distinct in most species Guinea worm female = 120 cm Male = 2.5 cm)

39 Excretory wastes collected by system of tubes Expelled through excretory pore in posterior end Longitudinal muscles, lack circular muscle -> thrashing motion Most free living

40 Many plant and animal parasites (enormous economic damage) Humans host 50 species More than 1/3 of humans infected

41 Ascaris Found in the intestines of pigs, horses, and humans Enter body in contaminated food or water Hatch in intestines Larvae bore into the blood stream

42 Carried to the lungs and throat Coughed up, swallowed, returned to intestines Mature and mate Block intestines -> death

43 Larvae in lungs cause respiratory illness Females produce 200,000 eggs/day (contain 27 million eggs) Shed through genital pore Exit in hosts feces

44 Ancylostoma and Necator - Hookworms Ancylostoma - effects 40 million people Necator - effects 360 million people Both tropical and semi- tropical Cutting plates hook into intestinal wall Feed on hosts blood -> anemia Attached to intestinal wall Migrating larvae

45 Travels via blood to lungs and throat where swallowed - > Mate in intestines -> Eggs shed in feces -> Hatch on moist soil -> Larvae bore through feet or new host

46 Trichinella Causes trichinosis Undercooked pork contaminated with cysts Cysts released larvae Larvae burrow into wall of small intestines

47 Mature into adults -> Adults produce larvae - > Pass into blood and form cysts in muscles -> Causing pain and suffering ->

48 Rotifera 1,750 species Transparent, free swimming and microscopic Freshwater and marine Crown of cilia surrounding mouth

49 Cilia sweep food into mouth Look like rotating wheel Feed on unicellular algae, bacteria, and protozoa Moves through pharynx -> mastax Mastax (muscular organ) chops up food

50 Hydrostatic pressure inside pseudocoelom Nervous system composed of anterior ganglia and two long longitudinal nerves Two anterior eye spots

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