Flatworms and Roundworm

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Flatworms and Roundworm

• Chapter 34
• 688-700
• http//www.microscopyu.com/moviegallery/pondscum/i
  ndex.html
• http//my.hrw.com/index.jsp

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Objectives 34.1

• Summarize the distinguishing characteristics of
  flatworms
• Describe the anatomy of a planarian
• Compare free-living and parasitic flatworms
• Diagram the life cycle of a fluke
• Describe the life cycle of a tapeworm

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P. Platyhelminthesflat worms

• The P. Platyhelminthes includes organisms called
  flatworms. Their bodies develop from three germ
  layers and are more complex than those of
  sponges, cnidarians, and ctenophores. Flatworms
  have bilaterally symmetrical bodies, with dorsal
  and ventral surfaces, right and left sides and
  anterior and posterior ends.

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Structure and Function of Flatworms

• Cephalization
• Free living
• Parasites (on or inside animals)
• Only one opening (mouth and anus)
• Freshwater or marine

• Simple
• Bilaterally symmetry
• Flat body
• Has 3 germ layers
• Acoelomates
• Gas exchange in skin (diffusion)

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Structure and Function of Flatworms

• 20000 species, 4 classes
• 1. c. Turbellarira
• 2. c. Trematoda
• 3. c. Monagenea
• 4. c. Cestoda

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1. c. TurbellariraA. Digestion and Excretion in
Planarians (Dugesia)

• 4500 species, Salt water and fresh water
• - scavengers of decaying plants and animals,
  small organisms
• Pharynx (throat) muscular tube that ingests food
  and sends food to the gastrovascular cavity?
  diffuses to other parts of the body
• Use flame cells (look like flickering candle
  flames) along with excretory tubules to remove
  excess water from hypotonic environments

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1. c. TurbellariraB. Neural control in Planarians

• More complex than cnidarians
• Cerebral ganglia- simple brain, two clusters of
  nerve cells at the anterior end
• Sensory cells transmit to nerves
• Eyespot- near the cerebral ganglia, can sense the
  intensity and direction of light
• Can also respond to touch, water currents and
  chemical in the environment

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1. c. TurbellariraC. Reproduction in Planarians

• Hermaphrodites
• Sexual reproduction- they simultaneously fetilize
  each other
• Eggs are in a capsules and stick to rocks (3wks
  to hatch)
• Can also reproduce asexually (summer)
• The worm will split in two- fission
• Worm can regenerate tail

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c. Trematoda and c. Monagenea

• Parasitic flukes (leaf-shaped flatworms)
• Parasite
• Endoparasites- live inside organism (blood,
  intestines, lungs, liver, other organs)
• Exctoparasites- external surfaces (fish and frogs)

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c. Trematoda and c. Monageneastructure of flukes

• Anterior suckers and ventral sucker
• Simple nervous system
• Tegument- outer covering made up of proteins and
  carbohydrates that is a defense mechanism
• Protects against digestive enzymes

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c. Trematoda and c. MonageneaReproduction and
life cycle flukes

• Hermaphroditic
• Fertilized eggs are store in uterus
• May release tens of thousands at one time
• Have more than one host

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Schistosoma

• Primary host- adult parasite gets its
  nourishment, sexual reproduction occurs (humans
  blood vessels)
• Excreted in wastes? fresh water system
• Becomes a ciliated larva and will attach a snail?
  will mature and develop a tail ? burrow into
  humans in water
• If eggs dont leave---- can be fatal
• 200million people world wide
• http//www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.a
  sp?bodyFrames/M-R/Opisthorchiasis/body_Opisthorch
  iasis_page1.htm

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Schistosoma
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c. Cestoda

• 5000 species of tapeworms
• Intestines of almost all vertebrates
• Eating raw or undercooked food containing eggs or
  larvae
• May cause digestion problems, weight loss, lack
  of energy, anemia, decrees in red blood cells

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c. Cestoda- Structure of Tapeworm

• Also have tegument
• Scolex- hooks and suckers to host
• Proglottids- long series of body sections
• Similar nervous/ excretory system to other
  flatworms
• Lack eyespots/ other light sensing organs
• No mouth, gastrovascular cavity, digestive organs
• Get nutrients by absorbing directly from host
  digestive track

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c. Cestoda- Reproduction and life cycle of
Tapeworm

• Hermaphrodites
• 1000000 or more eggs in the proglottid
• Tanenia saginatus-
• Has two host (human and cow)
• Cysts- dormant larvae

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34.2 Objectives

• Describe the body plan of a nematode
• Outline the relationship between humans and
  parasitic roundworms
• Describe the anatomy of a rotifer

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P. Nematoda

• Members of the phyla Nematoda are bilaterally
  symmetrical bodies that contain a fluid-filled
  space. This space holds the internal organs and
  serves as a storage area for eggs and sperm. It
  also supports the body and provides a structure
  against which the muscles can contract.

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P. Nematoda (roundworms)

• 15000 knows species, estimated 500,000
• Long slender bodies that taper at ends
• Pseudocoelomates
• 1mm to 120 cm
• Have a complete digestive tract (mouth-gut
  anus)
• Separate sexes
• Fresh and salt water, land
• Can be parasites of plants and animals
• http//www.microscopyu.com/moviegallery/pondscum/n
  ematode/index.html

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Ascaris

• Live in pig, horse, humans intestines
• Feed on food from host
• Can block hosts intestines
• 30cm long (1ft)
• 200,000 eggs every day, leave body in feces
• Can live in soil for years
• Contaminated food and water
• Larvae bore into bloodstream? lungs and throat ?
  to intestines
• Colonoscopy Demonstrating a Moving Worm
  http//www.youtube.com/watch?vHOaZCkA8Zvk

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Phylum Nematoda
Ascaris worms
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Hookworms

• Parasite (tropical and subtropical regions)
• Mouth has cutting plates hook on intestinal wall
• Can cause anemia
• Can cause slow mental development in children
• Larva live in soil ? boring through hosts feet ?
  travel to intestines
• Infect 1 billion people a year

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Trichinella

• Infect human, pigs and other mammals
• Eating undercooked meat
• Live in walls of host intestines
• Larvae are in cysts
• Causes Trichinosis, muscle pain and stiffness
• Cook and freeze at high temps to kill worms

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Other Parasitic roundworms pinworm, Enterobius

• Most common 50 in some areas
• Not serious
• 5-10mm, look like threads
• Live in lower region of intestines/ anus
• At night female exists and lays eggs
• Person scratches during sleep can be passed on to
  other persons
• Eggs must be ingested and will hatch in intestine

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Other Parasitic roundworms

• Filarial worms-
• Infect over 250 million in tropical countries
• Live in lymphatic system
• 100mm or 4in
• Enter blood passed by mosquitoes
• Causes swollen limbs and the skin hardens and
  thickens ? elephantiasis
• Toxocara or T. cati- heart worms of dogs and cats

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Ascaris Dissection

• http//www.youtube.com/watch?v_ybbnPj0t9Yfeature
  PlayListpE0DC6AAA94AFE60Fplaynext_fromPLplay
  next1index8

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Annelids

• Chapter 35
• 704-719
• http//www.microscopyu.com/moviegallery/pondscum/i
  ndex.html
• http//my.hrw.com/index.jsp

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35.2 objectives

• Identify the structures that provide the basis
  for dividing annelids into three classes
• List the advantages of body segmentation
• Describe the structural adaptation of earthworms
• Compare the three classes of annelids

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P. Annelida

• Colorful feather-dusters worms, common
  earthworms, and bloodsucking leaches are all
  members of the p. Annelida, a term that means
  little rings. The name refers to the many body
  segments that make an annelid look as if it is
  composed of a series of rings.

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Characteristics of annelids

• 15,000 species
• Bilaterally symmetrical
• Segmented worms
• True coelom
• One segment gets injured can still surrive
• External bristles setae
• Parapodis- fleshy protrusions
• 3 classes
• C. Oligochaeta 2. C. Polycheaeta
• 3. C. Hirudinea

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Class Oligochaeta- few bristles, few setae

• Live in soil or fresh water
• No parapodia
• ? How can this animal burrow
• 1. Structure and movement
• - 100 segments
• - contract circular muscles to move

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Class Oligochaeta cont

• 2. Feeding and Digestion
• Ingest soil as burrow ? mouth ? pharynx ? to
  esophagus? crop ? gizzard ? absorption of
  nutrients (typhlosole)
• Maintaining fertility of soil (decompose leaves),
  air to roots of plants, loosen soil
• 3. Circulation
• Closed system
• 5 pairs of aortic arches

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Class Oligochaeta cont

• 4. Respiration and excretion
• Diffuse directly through skin (gas exchange)
• Need to keep skin moist (cuticle/ mucus)
• Nephridia- excretory tubules
• 5. Neural control
• Chain of ganglia connected by a ventral nerve
  cord
• Anterior end- cerebral ganglia or brain
• Respond to light, touch, chemicals, temp., moist

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Class Oligochaeta cont

• 6. Reproduction
• Hermaphrodites
• Can not fertilize its own egg
• Ventral surfaces must join anterior ends pointing
  in opposite direction, held together by setae and
  film of mucus secreted by the clitellum
• Sperm is injected into mucus pass to seminal
  receptacle
• Fertilization occurs inside 2-3 wks to hatch

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C. Polycheaeta- many bristles

• Many bristles help them move
• 2/3 of all annelids
• Antennae
• Specialized mouth parts
• Trochophore stage
• Marine habitats
• Free swimming
• Some eat sediments in ocean

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C. Hirudinea

• Smallest of all annelids
• 500 species of leeeches
• Fresh water
• Mosit vegetation
• No setae or parapodia
• Sucker
• Secret an anaesthetic
• Can ingest 10 times own weight in blood

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OKto end to a peaceful note, these, too, are
segmented worms.
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virtual

• http//www.mhhe.com/biosci/genbio/virtual_labs/BL_
  14/BL_14.html
• http//shs.westport.k12.ct.us/mjvl/biology/dissect
  /earthworm.htm
• http//biog-101-104.bio.cornell.edu/BioG101_104/tu
  torials/animals/earthworm.html
• https//meyerbio3.wikispaces.com/Annelida

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Dissections

• http//www.flushing.k12.mi.us/srhigh/mignerey/web
  20dissections/earthworm20web/Frameset.htm
• http//www.youtube.com/watch?vA2BY0hRUA9E
• http//www.mhhe.com/biosci/genbio/virtual_labs/BL_
  14/BL_14.html

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