Transcript Invertebrates: Phylum Porifera - hills

Invertebrates: Phylum Porifera
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Sponges
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Multicellular; body a loose aggregate of cells
All aquatic, mostly marine
 Body with pores (ostia), canals, and chambers for
circulation of water
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◦ Epidermis of flat cells, some with contractile fibers
◦ Middle layer is semi-fluid, with wandering amebocytes
◦ Inner layer of choanocytes-flagellated to move water
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Phylum Porifera cont’d
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Filter feeders- intracellular digestion
◦ Cells get food from circulating water
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Classified based on skeleton
◦ Composed of spicules
 Chalk sponges - spicules of calcium carbonate
 Glass sponges - spicules of silica
 Proteinaceous sponges - spongin fibers
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Reproduction
◦ asexual by budding, sexual by fusion of gametes
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Sponge
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Fig. 30.3
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Invertebrates: Phylum Cnidaria
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Cnidarians
◦ Multicellular, tubular or bell-shaped animalsradial symmetry
◦ All aquatic, mostly marine
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2 germ layers during development
◦ Organized at tissue level
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Nematocysts
◦ stinging cells unique to cnidarians
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Cnidarians cont’d
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2 body types-polyps and medusae
◦ Life cycle alternates between both forms in some;
in others one form is reduced or absent
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Gastrovascular cavity-sac-like body plan
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Includes corals, jellyfish, and hydrozoans
◦ Corals- polyps
◦ Jellyfish-medusae
◦ Hydrozoans-may have both forms
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Cnidarian diversity
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Fig. 30.4
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Cnidarians cont’d
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Hydra
◦ Representative organism (Class Hydrozoa)
◦ Freshwater, attaches to rocks, leaf litter
◦ Small tubular polyp, sac-like body plan with a
single opening
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Outer tissue layer – epidermis from ectoderm
Inner layer – gastrodermis from endoderm
Longitudinal and circular muscle fibers present
Diffuse nerve net between layers
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Cnidarians cont’d
◦ Digestion begins in gastrovascular cavity,
completed in cells
◦ Can reproduce sexually and asexually
(budding)
 Sexual reproduction- hydra develops an ovary or
testis in body wall-produces gametes
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Anatomy of Hydra
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Fig. 30.5
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Invertebrates: Phylum Platyhelminthes
Flatworms
 Bilateral symmetry, three germ layers,
acoelomate
 Mesoderm gives greater complexity
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◦ Muscles, excretory, reproductive, and digestive
systems in some
◦ Respiration by diffusion and circulation
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Platyhelminthes cont’d
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Class Turbellaria - Planarians
◦ Free-living flatworms
◦ freshwater, feed on small living and dead
organisms
◦ Ladder-like nervous system
 Ganglia and eyespots anterior
 Auricles – chemosensitive receptores
◦ Digestion:
 Feed through muscular pharynx
 Specialized cells for excretion: flame cells
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Platyhelminthes cont’d
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Class Turbellaria - Planarians cont’d
◦ 3 muscle layers- circular, longitudinal, and
diagonal
 Allows for more complex movements
◦ Cephalization
 Organized to have an anterior end and a posterior
end
◦ Hermaphroditic
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Planarian
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Fig. 30.6
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Parasitic Platyhelminthes
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Class Cestoda (Tapeworms)
◦ Internal parasites as adults
◦ Body Structure
 Tegument: tough outer covering
 protect from host’s enzymes
 Scolex - head
 Barbs/hooks for attachment
 Proglottids: segments
 Each contains organs of both sexes
◦ Lack a digestive system- why?
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Parasitic Platyhelminthes cont’d
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Class Cestoda (Tapeworms) (cont’d)
◦ Reproduction
 Fertilization is internal
 proglottids filled with fertilized eggs are called gravid
 Gravid proglottids drop off and pass out in feces
 Ingested by intermediate host
 larvae become encysted
 Intermediate host is then eaten by definitive host
 Larvae mature to adults
◦ Representative Organism: Tanea solium
 Pork tapeworm
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Life cycle of a tapeworm, Taenia
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Fig. 30.7
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Parasitic Platyhelminthes cont’d
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Class Trematoda - Flukes
◦ Endoparasites of many species
◦ Body Structure
 Tegument
 Oral sucker and posterior sucker
◦ Digestion
 Well-developed digestive canal
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Parasitic Platyhelminthes cont’d
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Class Trematoda - Flukes cont’d
◦ Muscles and excretory system much like freeliving flatworms
 Poorly developed sense organs- why might that be?
◦ Reproduction
 Hermaphroditic
 Complex life cycle involving two intermediate hosts
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Parasitic Platyhelminthes cont’d
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Class Trematoda - Flukes cont’d
◦ Representative Organism: Clonorchis sinensis
 Liver Fluke
 Transmission
 Snails ingest eggs
 Develop in to larvae, which leave the snail and burrow into
muscles of a fish
 Humans ingest fish
 Larvae moves into bile ducts where adults develop
 Eggs pass out of human in feces, cycle continues
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Invertebrates: Phylum Nematoda
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Roundworms
◦ First appearance of
 Tube-within-a-tube body plan
 2 openings, mouth and anus
 Body Cavity
 Pseudocoelomates
 Pseudocoel -filled with fluid, acts as hydrostatic skeleton
◦ Many species; some are free-living in soil and
water, others are parasitic
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Coelom structure and function
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Fig. 30.8
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Parasitic Nematodes
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Ascaris
◦ Move with whip-like motion
◦ Intestinal parasites in many animal species
◦ Females are much longer than males and highly
prolific
◦ Eggs enter host in uncooked vegetables, soil, or
feces
 Larvae burrow out of intestine and migrate to heart and
lungs
 Larvae are coughed up and swallowed
 Mature to adults in intestines
 Estimated to infect 25% of world population
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Roundworm anatomy
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Fig. 30.9
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Parasitic Nematodes cont’d
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Trichinella spiralis
◦ the trichina worm
◦ Causes trichinosis
◦ Humans contract the worm by eating
undercooked pork
◦ Larvae migrate out of intestines and form
painful cysts in the muscles
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Parasitic Nematodes
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cont’d
Wuchereria bancrofti
◦ filarial worm that
causes elephantiasis
◦ Migrates into
lymphatic vessels and
prevents lymph
drainage
◦ Edema occurs
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Parasitic Nematodes
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cont’d
Pinworms and hookworms
◦ Roundworm parasites which cause problems
in children
◦ Much more common in U.S.
 Pinworms are primarily an annoyance
 Hookworms cause skin irritations and in some
cases debilitating disease
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