flat worms. phylum platyhelminthes simple animals with soft leaflike or ribbonlike bodies, and...
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Phylum PlatyhelminthesPhylum Platyhelminthes Simple animals with soft leaflike or Simple animals with soft leaflike or
ribbonlike bodies, and includes ribbonlike bodies, and includes flatwormsflatworms, , flukesflukes, and , and tapewormstapeworms
Around Around 20,00020,000 species species Body is unsegmentedBody is unsegmented Bilaterally symmetricalBilaterally symmetrical Called “flatworms” because bodies Called “flatworms” because bodies
are flattened are flattened dorso-ventrallydorso-ventrally
Phylum PlatyhelminthesPhylum Platyhelminthes AcoelomatesAcoelomates-solid bodies without a lined -solid bodies without a lined
body cavity; internal organs lie in a loose body cavity; internal organs lie in a loose tissue called tissue called parenchymaparenchyma
3 body layers3 body layers: ectoderm, mesoderm, : ectoderm, mesoderm, endodermendoderm
Show Show cephalizationcephalization (concentration of (concentration of sensory organs at anterior or head end)sensory organs at anterior or head end)
No circulatory system; body cells No circulatory system; body cells exchange oxygen & carbon dioxide exchange oxygen & carbon dioxide directly with environment by directly with environment by diffusiondiffusion
Phylum PlatyhelminthesPhylum Platyhelminthes Single opening into gastrovascular Single opening into gastrovascular
cavity: cavity: two-way digestive tracttwo-way digestive tract In some a In some a tubular pharynxtubular pharynx can be can be
projectedprojected Mouth located at the front, ventral endMouth located at the front, ventral end Water balance is maintained by Water balance is maintained by
excretory tubules (excretory tubules (protonephridiaprotonephridia) ) equipped with flame cellsequipped with flame cells
Phylum PlatyhelminthesPhylum Platyhelminthes Nervous system: Nervous system: brain and nerve cordsbrain and nerve cords
extending along the bodyextending along the body Circular, longitudinal, and other muscle Circular, longitudinal, and other muscle
fibers enable turning, twisting, and fibers enable turning, twisting, and folding of the bodyfolding of the body
Free-living flatworms move by means of Free-living flatworms move by means of a a ciliated epidermisciliated epidermis and undulations of and undulations of the bodythe body
Parasitic flatworms have thick cell layer Parasitic flatworms have thick cell layer called called tegumenttegument covered by a nonliving covered by a nonliving cuticlecuticle covering their bodies as covering their bodies as protection inside hostsprotection inside hosts
Phylum PlatyhelminthesPhylum Platyhelminthes Mostly hermaphroditesMostly hermaphrodites Sperm and egg are exchanged during Sperm and egg are exchanged during
mutual copulationmutual copulation; internal fertilization; internal fertilization Asexual reproduction by Asexual reproduction by fragmentation fragmentation
and regenerationand regeneration Parasitic species have complex life cycles Parasitic species have complex life cycles
- with several larval stages often with two - with several larval stages often with two or more different hostsor more different hosts
ClassificationClassification Class TurbellariaClass Turbellaria
DugesiaDugesia (planarian)(planarian)
Class Trematoda Class Trematoda (flukes)(flukes) SchistosomaSchistosoma
Class Cestoda Class Cestoda (tapeworms)(tapeworms)
Class Turbellaria Class Turbellaria (Planaria)(Planaria) Most are marine but include Most are marine but include
freshwater planarian (freshwater planarian (DugesiaDugesia)) Spade-shaped anterior end with Spade-shaped anterior end with
light-sensitive light-sensitive eyespotseyespots 2 clusters of nerve cells (2 clusters of nerve cells (gangliaganglia) to ) to
form a simple brain and a nerve netform a simple brain and a nerve net Capable of simple learningCapable of simple learning
Class Turbellaria Class Turbellaria (Planaria)(Planaria)
Move by Move by ciliacilia Feed by Feed by scavengingscavenging or protozoans or protozoans Mouth located at the end of Mouth located at the end of
muscular tube called the muscular tube called the pharynxpharynx which is extended when feedingwhich is extended when feeding
Flame cellsFlame cells help remove wastes to help remove wastes to excretory poresexcretory pores
Class Turbellaria Class Turbellaria (Planaria)(Planaria)
Hermaphrodites that cross-fertilize Hermaphrodites that cross-fertilize eggs; deposited into a capsule until eggs; deposited into a capsule until hatching in 2-3 weekshatching in 2-3 weeks
Reproduce asexually by Reproduce asexually by fragmentationfragmentation
Class Turbellaria Class Turbellaria (Planaria)(Planaria)
Pharynx
Mouth
Gastrovascular Cavity
Nerve Cords
EyespotsBrain
Class Trematoda (Flukes)Class Trematoda (Flukes)
Includes parasitic flukesIncludes parasitic flukes Most around 1 cm long and oval Most around 1 cm long and oval
shapedshaped Require a Require a hosthost to live to live Have Have oral and ventral suckersoral and ventral suckers to cling to cling
to host & suck blood & body fluidsto host & suck blood & body fluids EndoparasitesEndoparasites: live inside a host: live inside a host EctoparasitesEctoparasites: live on outside of host: live on outside of host
Class Trematoda (Flukes)Class Trematoda (Flukes)
Covered in tough, unciliated Covered in tough, unciliated tegumenttegument
Nervous & excretory systems like Nervous & excretory systems like turbellariansturbellarians
HermaphroditesHermaphrodites Long, coiled uterus stores & releases Long, coiled uterus stores & releases
10,000+ eggs10,000+ eggs Eggs released through Eggs released through genital poregenital pore & &
develop into larvadevelop into larva
Class Trematoda (Flukes)Class Trematoda (Flukes)Life cycle of sheep liver fluke (Life cycle of sheep liver fluke (Fasciola Fasciola
hepaticahepatica):):1.1. Adult liver flukes live in sheep Adult liver flukes live in sheep liver & gall liver & gall
bladderbladder where they mate & form eggs where they mate & form eggs
2.2. Eggs enter intestines, pass out with feces, & Eggs enter intestines, pass out with feces, & hatch in waterhatch in water
3.3. Larva enter Larva enter snailssnails, asexually multiply, then , asexually multiply, then leave snail & form cystsleave snail & form cysts
4.4. CystsCysts (dormant larva with hard, protective (dormant larva with hard, protective covering) clings to grasscovering) clings to grass
5.5. Sheep ingest cysts when they eat grassSheep ingest cysts when they eat grass
6.6. Cysts hatch in Cysts hatch in digestive tractdigestive tract & bore through & bore through intestines into intestines into bloodstreambloodstream
7.7. Mature and reproduce in the liverMature and reproduce in the liver
Class Trematoda (Flukes)Class Trematoda (Flukes) SchistosomiasisSchistosomiasis::
disease caused by disease caused by parasitic blood parasitic blood flukes flukes ((Schistosoma)Schistosoma); ; infects people in infects people in Asia, Africa, and Asia, Africa, and South America South America causing intestinal causing intestinal bleeding and bleeding and tissue decay that tissue decay that can result in deathcan result in death
Class Cestoda Class Cestoda (Tapeworms)(Tapeworms) Adapted for Adapted for parasitic lifeparasitic life
Tough outer Tough outer tegument prevents tegument prevents being digested by being digested by hosthost
ScolexScolex: anterior : anterior end, contains end, contains hooks & suckers hooks & suckers for attachment to for attachment to intestine of hostintestine of host
Class Cestoda Class Cestoda (Tapeworms)(Tapeworms)
Long, ribbon-like bodies up to Long, ribbon-like bodies up to 12 m12 m in lengthin length
Nervous system extends length of Nervous system extends length of body but body but lacks sense organslacks sense organs
Lacks mouth and digestive tract; Lacks mouth and digestive tract; absorbs digested nutrients from absorbs digested nutrients from hosthost
Grows by making body segments Grows by making body segments called called proglottidsproglottids
Class Cestoda Class Cestoda (Tapeworms)(Tapeworms)
Each proglottid produces eggs & Each proglottid produces eggs & sperm that cross-fertilize with other sperm that cross-fertilize with other segments & also self-fertilize segments & also self-fertilize (hermaphrodites)(hermaphrodites)
Oldest, mature proglottids Oldest, mature proglottids containing eggs at posterior end; containing eggs at posterior end; break off & pass out with fecesbreak off & pass out with feces
Class Cestoda Class Cestoda (Tapeworms)(Tapeworms) Life cycle of beef tapewormLife cycle of beef tapeworm::
1.1. Cattle eat grass with Cattle eat grass with proglottids containing proglottids containing fertilized eggsfertilized eggs
2.2. Eggs hatch into larva & Eggs hatch into larva & bore through cow’s bore through cow’s intestine into bloodstreamintestine into bloodstream
3.3. Larva burrow into cow’s Larva burrow into cow’s muscle & form cystsmuscle & form cysts
4.4. Humans eat beef (muscle) Humans eat beef (muscle) & cysts travels to & cysts travels to intestinesintestines
5.5. Cyst breaks open & adult Cyst breaks open & adult beef tapeworm formsbeef tapeworm forms