Download Mollusks and Annelids

Flatworms and Roundworm
Chapter 34
688-700
http://www.microscopyu.com/moviegallery/pondscum/index.html
http://my.hrw.com/index.jsp
Modern Biology:
Chapter 34
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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. Platyhelminthes
flat 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
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Simple
Bilaterally symmetry
Flat body
Has 3 germ layers
Acoelomates
Gas exchange in skin
(diffusion)
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• Cephalization
• Free living
• Parasites (on or
inside animals)
• Only one opening
(mouth and anus)
• Freshwater or marine
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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. Turbellarira
A. 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. Turbellarira
B. 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. Turbellarira
C. 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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Modern Biology:
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c. Trematoda and
c. Monagenea
structure 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. Monagenea
Reproduction and life cycle flukes
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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 don’t leave---- can be fatal
• 200million people world wide
http://www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.asp?body=Frames/MR/Opisthorchiasis/body_Opisthorchiasis_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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Modern Biology:
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c. CestodaStructure of Tapeworm
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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. CestodaReproduction and life cycle of
Tapeworm
• Hermaphrodites
• 1000000 or more eggs in the proglottid
Tanenia saginatusHas 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)
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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/nematode/ind
ex.html
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Ascaris
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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?v=HOaZCkA8Zv
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k Biology:
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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 host’s
feet  travel to intestines
• Infect 1 billion people a year
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Trichinella
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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
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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=_ybbnPj
0t9Y&feature=PlayList&p=E0DC6AAA94A
FE60F&playnext_from=PL&playnext=1&in
dex=8
Modern Biology:
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Annelids
Chapter 35
704-719
http://www.microscopyu.com/moviegallery/po
ndscum/index.html
http://my.hrw.com/index.jsp
Modern bio: Chapter 35
Mollusks and Annelids
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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
Modern bio: Chapter 35
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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
1. 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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Mollusks and Annelids
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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. Polycheaetamany bristles
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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
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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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OK…to 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/B
L_14.html
• http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthwo
rm.htm
• http://biog-101104.bio.cornell.edu/BioG101_104/tutorials/animals/earth
worm.html
• https://meyerbio3.wikispaces.com/Annelida
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Dissections
• http://www.flushing.k12.mi.us/srhigh/migne
rey/web%20dissections/earthworm%20we
b/Frameset.htm
• http://www.youtube.com/watch?v=A2BY0h
RUA9E
• http://www.mhhe.com/biosci/genbio/virtual
_labs/BL_14/BL_14.html
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