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Parazoa
Eumetazoa
Bilateria
Radiata
Coelomates
Pseudocoelomates
Protostomia
Ctenophora
Porifera
Cnidaria
Acoelomates
The Animal Kingdom:
The Protostomes
Deuterostomia
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
Chapter 30
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Parazoa
Eumetazoa
Bilateria
Platyhelminthes
Radiata
Ctenophora
Porifera
Acoelomates
Cnidaria
Protostomes
Fig. 29-7, p. 627
Coelomates
Pseudocoelomates
Protostomia
• Characterized by
– spiral cleavage
– determinate cleavage (fixed fate of cells)
– development of mouth from blastopore
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Phylum Platyhelminthes
(Flatworms) - 20,000
spp.
• Acoelomate animals with:
– bilateral symmetry
– cephalization
– 3 definite tissue layers
– well-developed organs
• Many are hermaphrodites
– single animal produces both sperm and eggs
Fig. 29-7, p. 627
Phylum Platyhelminthes
(Flatworms)
• Ladder-type nervous system
– sense organs
– simple brain composed of two ganglia
– 2 nerve cords that extend the length of body
• Protonephridia
– function in osmoregulation and disposal of
metabolic wastes
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3 Classes of
Phylum Platyhelminthes
Protonephridia
• Class Turbellaria
– free-living flatworms, including planarians
Flame bulb
• Classes Trematoda and Monogenea
– parasitic flukes
• Class Cestoda
– parasitic tapeworms
Fig. 28-13
Class: Turbellaria
Ganglia
Carnivorous
Auricle
Auricle
????
Eyespot
Class turbellaria
e.g. planarians
Nerve
Gastrovascular
cavity
Pharynx
Food in
Sexual (hermaphrodites)
+ asexual
Sheath
surrounding
pharynx
Undigested
out
Mouth
Gasses via diffusion
Protonephridia
1 mm
Fig. 28-13
Fig. 30-1ab, p. 642
Class: Trematoda (Monogenea) Flukes
•
•
•
•
Look like free living flatworms - BUT
Modified body plan - suckers for clinging to host
Complex life cycle that may involve several hosts
Large number of eggs
Liver Fluke
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Do not post photos on Internet
2. Larvae make their way to the
circulatory system. During
reproduction, which takes place
in the intestinal veins, the male
holds the female in a long groove.
1. Larvae burrow
through the skin.
3. Eggs pass into
the intestine.
7. Finally, fork-tailed larvae
(cercariae) develop and
leave the snail.
4. Eggs containing developing
embryos are excreted with
the feces.
6. The larvae must enter a second
host, a freshwater snail. After
burrowing into the tissues of the
snail, larvae develop into a form
that reproduces asexually. This
process greatly increases the
number of larvae.
5. If they find their way to fresh
water, the eggs hatch, releasing
free-swimming larvae (miracidia).
Blood Fluke
Fig. 28.15
Slide 19
Trematoda
Class: Cestoda (tapeworms)
5,000 species
Long, flat ribbon like animals
Head (scolex) that attaches to intestine and absorbs
digested food
Body a long chain of proglottids
No mouth – no digestive system
Proglottids
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Tapeworm
Parazoa
Eumetazoa
Bilateria
Platyhelminthes
Radiata
Nemerteans
Ctenophora
Porifera
Cnidaria
Acoelomates
Coelomates
Pseudocoelomates
Protostomia
Deuterostomia
Nemerteans
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Fig. 29-7, p. 627
Phylum: Nemertea
(ribbon worms or proboscis worms)
•
•
•
•
900 species
Free living critters – marine habitats
Characterized by proboscis
Coelom (rhynchocoel)
• carnivorous!!!
• Separate sexes
• Evolutionary milestones!!
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Parazoa
Eumetazoa
Bilateria
Nemerteans
Porifera
Cnidaria
Phylum: Nemertea
Ctenophora
Acoelomates
Coelomates
Pseudocoelomates
Nematoda
Platyhelminthes
Radiata
Protostomia
Deuterostomia
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
1st blood vessels????!!!!!
Complete digestion???!!!!!!!!!
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Nematoda - The Roundworms (20,000 spp.)
New major grouping - Pseudocoelomate animals
• Decomposition and nutrient recycling
• Free living and parasitic
• Pseudocoelom acts as a hydroskeleton
Complete digestive tract (mouth and anus)
Three germ tissue layers
No circulatory system
• Sexes separate
• Body covered by tough cuticle
– helps prevent desiccation
Fig. 29-7, p. 627
Phylum Nematoda (Roundworms)
• Parasitic nematodes in humans
– Ascaris
– hookworms
– trichina worms
– pinworms
Ascaris
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Parazoa
Eumetazoa
Bilateria
Coelomates
Pseudocoelomates
Protostomia
Phylum Rotifera
Deuterostomia
Rotifera
Nemerteans
Ctenophora
Porifera
Cnidaria
Acoelomates
Nematoda
Platyhelminthes
Radiata
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
•
•
•
•
•
•
•
•
~ 2000 spp.
Most Marine
Recycling of nutrients
Characteristic crown of cilia
Brain – sense organs – eye spots
Protonephridia
“cell constant”
Dormancy!!! For months/years
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Fig. 29-7, p. 627
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Parazoa
Eumetazoa
Bilateria
Onychophora
Pseudocoelomates
Tardigrada
Coelom
Coelomates
Protostomia
Rotifera
Nemerteans
Ctenophora
Porifera
Cnidaria
Acoelomates
Nematoda
Platyhelminthes
Radiata
Deuterostomia
• True coelom is a fluid-filled body cavity
– completely lined by mesoderm between digestive
tube and outer body wall
Segmentation
Segmentation
Pseudocoelom
Deuterostome
development
True coelom
Radial
symmetry
Protostome development
Three tissue layers (mesoderm)
Bilateral symmetry
Tissues (ectoderm and endoderm)
Multicellularity
Choanoflagellate
ancestor
Phylum: Tardigrada
• Tiny with unbranched clawed legs
• Allows tube-within-a-tube body plan
– body wall is outer tube
• inner tube is digestive tubeA space in which internal
organs develop
– including gonads!
• Helps transport materials
• Protects internal organs
Fig. 29-7, p. 627
Phylum Onychohoran
• Paired appendages not jointed
• Jaws are derived from appendages
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