Page 1
How does Cnidaria fit in?
Porifera
unknown common ancestor
eukaryotemulticellular
heterotrophicBlastula stage
cellular level of organization
choanocytes
3 body types
Cnidaria
tissue level of organization
diploblastic
3 classes:Hydrozoa, Scyphozoa, Anthozoa
2 body types: polyp, medusa
Page 2
How do the Acoelomates fit in?
Porifera
unknown common ancestor
Cnidaria
Platyhelminthes Nemertea
the acoelomates
Page 4
Acoelomate Characteristics
Organ level of organization
Tissues are organized to for organs which are used to accomplish physiological functions
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Acoelomate Characteristics
3 Embryonic Germ Layers
endoderm
mesoderm
ectoderm
3 Tissue Layers
gastrodermis
mesoderm
epidermis
Triploblastic
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Acoelomate Characteristics
No body cavity
Gut
ectoderm
mesoderm
endoderm
ectoderm
mesoderm
endoderm
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Acoelomate Characteristics
Ectoderm
Endoderm
Mesoderm (mesenchyme, parenchyma)
Gut
Triploblastic
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Acoelomate Characteristics
Anterior: toward the front of the body
Posterior: toward the rear of the body
Bilateral Symmetry
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Acoelomate CharacteristicsCephalization
Eye spots
Auricles
the concentration of sensory organs in the head of the animal
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Phylum Platyhelminthes
the flatworms
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Physiology
Feeding– Free-living, carnivorous – parasitic
Digestion– intestine is simple or branched– incomplete system (no anus)– digestive system reduced or absent
in parasitic species
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Physiology
Osmoregulation and excretion – Protonephridia and flame cells– much excretion is via diffusion
protonephridia flame cell
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Physiology
Nervous system-ladder-like
-cephalization
-nervous system is
reduced in parasitic
species
Lateral nerve cords
Cerebral ganglia
Skeletal and circulatory systems– absent
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Physiology
Reproduction
Asexual
Sexual– usually monoecious, but most must cross
fertilize– Internal fertilization (usually reciprocal)
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Phylum Platyhelminthes
Class Turbellaria
Class Trematoda
Class Cestoda
Page 16
Class TurbellariaFree-living flatworms
• move on slime trails using cilia
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Class Turbellaria
• predatory
• use a pharynx to capture prey
pharynx
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Class Turbellaria
• have a branched (or lobed) gut
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ClassTurbellaria
Reproduction
Asexual– Fission
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ClassTurbellaria
Reproduction
Sexual– internal fertilization– simple life cycle
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Adaptations for Parasitism
• increased reproductive potential• monoecious• presence of adhesion organs (suckers, hooks)• poorly developed sensory systems• reduced, or absent, digestive system• resistant cuticle• complex life cycles with more than 1 host
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Class Trematoda
Parasitic Flukes
• endoparasitic
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Trematoda Life Cycle• have at least two hosts in their life cycle• final host = vertebrate
adult fluke (in host liver)
Vertebrate host #1
infective stage in host muscle
Vertebrate host #2
Invertebrate host eats eggs
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Class Cestoda
Parasitic tapeworms
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Class Cestoda
scolex
proglottids
2 body regions: scolex and proglottids
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Class Cestoda
Scolex suckers
rostellum
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Class Cestoda
Proglottids • repeating segments containing reproductive organs
• may be immature, mature, or gravid
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Class Cestoda
Immature proglottids
• found at the anterior end of the tapeworm
• contain no noticeable sex organs
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Class Cestoda
Mature proglottids
• found in the middle of the tapeworm
• contain noticeable sex organs
• sperm must come from either a different proglottid or a different individual
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Class Cestoda
genital pore
ovary
uterus
testes
sperm duct
vagina
Mature proglottids
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Class Cestoda
Gravid proglottids
• found at the posterior end of the tapeworm
• contain fertilized eggs
• entire proglottid is shed in the host’s feces
eggsuterus
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Cestoda Life CycleAdult tapeworm (in host intestine)
Gravid proglottids
eggs
Vertebrate host #1
Infective stage in host muscle
Vertebrate host #2
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Ecology
•Parasitic flatworms infect many people in some parts of the world (for example, the Chinese liver fluke infects approx. 30 million people in Asia)
•Some Trematodes have display polyembyony: a single larvae can have up to 4 younger larvae developing within it
•Trematodes are a model system for studying host parasite coevolution
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Phylum Nemerteathe ribbonworms
Page 35
Physiology
Feeding– Free-living, carnivorous – have an eversible proboscis that is
not connected to the digestive system
– Proboscis is used to stab prey and may have a poisonous tip (or stylet)
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Physiology
rhynchocoel
proboscis
mouth
rhynchocoel
Page 37
Physiology
Digestion– intestine is unbranched– complete system (mouth and anus)
This is the first animal to have an anus!!!
Page 38
Physiology
Reproduction
Asexual– Some species are capable of reproducing
asexually through fragmentation and regeneration
Sexual
– usually dioecious
– internal fertilization
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Physiology
Osmoregulation and excretion
– same as Platyhelminthes
Nervous system– same as Platyhelminthes
Skeletal systemsame as Platyhelminthes
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Physiology
Circulation– closed circulatory system
consisting of contractile blood vessels
This is the first animal to have a closed circulatory system!!!
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Ecology
•Nemerteans are mostly marine, although there are a few species found in freshwater (and even a few on land!)
•They range in size from a few millimeters to 30 meters
•Their biology is little known in part because they are extremely fragile and fragment easily
Page 42
How do the acoelomates fit in?
Porifera
unknown common ancestor
Cnidaria
triploblastic
organ level of organization
Platyhelminthes
protonephridia
cephalization
Ladder-like nervous system
Nemertea
proboscis
Complete digestive system
Closed circ. systemacoelomate
acoelomate