Transcript Survey of the phyla: Porifera through Annelida

Survey-Animal Kingdom I
Porifera  Cnidaria 
Platyhelminthes  Nematoda
Annelida
Review of Animal Development
Phylum Porifera
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Belongs to Parazoa
(beside the animals)
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Evolved from colonial
protozoans
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Evolutionary “dead end”
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Most primitive animals
Sponges
come in many colors…
Phylum Porifera
General characteristics:
 pore-bearing animals
 sessile
 most are marine
 asymmetrical
 diploblastic
  5,000 species
Porifera General Construction
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“one hole sac”
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central cavity = spongiocoel
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water enters through ostium
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water exits through osculum
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filter feeders: algae, bacteria,
organic debris
Anatomy of a Sponge
Anatomy of a Sponge
Porifera Anatomy
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choanocytes or collar cells-
create
water currents for circulation & feeding
spicule-skeletal element for support
 amoebocyte-transport of nutrients from
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choanocytes to non-feeding cells
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mesenchyme-gelatinous protein colloid; not
a cellular layer
Porifera Reproduction
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Asexual – budding, regeneration,
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Sexual- sperm and ova arise from
gemmules
ameobocytes or choanocytes
– Sponges are monoecious (one house)
which is a reference to both sperm and
ova production by a single organism
Development of a Sponge
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1) Zygote
2) Embryo
3) Breaks open & everts
4) Larvum (amphiblastula)
5) Invaginates to form sessile adult
Classification of sponges
Based on canal system:
 Ascon – simplest 2 layer sac;
Leucosolenia
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Sycon – surface is folded to increase
surface area; Grantia
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Leucon – most advanced & successful; permits
maximum surface & size; surface deeply folded
to form systems of canals; commercial sponges
Classification of sponges
Based on spicule type:
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Calcium spicules – CaCO3 (calcium
carbonate); chalk sponges
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Silicon spicules – Si3O2; glass sponges
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Spongin spicules – organic or horny;
natural commercial sponges
Phylum Cnidaria
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Subkingdom Eumetazoa:
organ, organ system level of development
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Grade Radiata: radial symmetry
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Coelenterata –
“hollow gut or cavity” –
gastrovascular cavity
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Name derived from cnidocytes:
specialized stinging cells around mouth & tentacles
Close-up of a Cnidocyte
Two basic structural forms:
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Polyp
1) sessile
2) asexual: budding
3) sexual: gamete production
Medusa
1) motile
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2) sexual only
 One or both may occur in a given life
cycle
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Anatomy of a Cnidarian
General Construction:
3 “layer” but Diploblastic
 1) epidermis- (ectoderm)
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epidermal cells
cnidocytes
longitudinal muscles cells
gland cells
nerve cells connected to
sensory receptor cells =
nerve net
General Construction:
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2) mesoglea
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”middle glue”
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gelatinous colloid layer/ not a
true cellular layer – cells found
here originate in other layers
General Construction:
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3) gastrodermis
lines gastrovascular cavity
circular muscle
flagellated nutritive cells
gland cells -secrete digestive enzymes
into cavity. Food is partly digested
extracellularly. Digestion is completed
in the nutritive cells.
Obelia Life Cycle
Obelia Life Cycle
Obelia Life Cycle
z
Obelia Life Cycle
Cnidarian Life Cycle
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Many exhibit a life cycle which is
superficially plant-like because it
alternates between the two body
forms: polyp and medusa.
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Cnidarians exhibit the Diplontic Life
Cycle as do all animals (only the
gametes are 1N)
Obelia Life Cycle
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Cnidaria life cycle allows for
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1) rapid asexual reproduction by polyp
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2) dispersal & genetic recombination by
medusa
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3) habitat selection by planula larvum
Classification of Cnidaria
See pictures in Campbell, 5th ED, Chapter 33, page 602
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Class Hydrozoa –
polyp is dominant
 colonial polyps w/high degree of specialization
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Hydra – polyp only
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Obelia – both forms
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Physalia – both forms
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Gonionemus – both forms
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Hydrozoan polyps
Classification of Cnidaria
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Class Scyphozoa
medusa is dominant
“jellies”
Aurelia – true jelly fish
JELLY MEDUSA
Lion Mane Jelly
Purple-stripped Jelly
Classification of Cnidaria
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Class Anthozoa
all marine
 no medusa
 feed on mollusks, crustaceans, small fish
 Metridium – sea anemones
 Corals
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Anthozoan: Sea Anemone
Coral polyps
THIS
ENDS
THE
PHYLUM
CNIDARIA
AND
BEGINS
THE
PHYLUM
PLATYHELMINTHES
Grade Bilaterata
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Triploblastic
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All members exhibit bilateral
symmetry at some point; either
ancestral forms, larval form, or
adult form
Subgrade Acoelomata
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no body cavity
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solid mesoderm
no respiratory tract since no cell
is more than a few mm away from
surface
 digestive cavity is branched
carrying food to all regions
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Phylum Platyhelminthes
General characteristics:
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triploblastic
flattened dorsoventrally
exhibit cephalization: anterior & posterior
freshwater, marine, terrestrial
both free living and parasitic
incomplete digestive tract: mouth = anus
General construction
epidermis
mesoderm
incomplete digestive tract
gastrodermis
platy = flat
helminthes = worm
Classification
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Class Turbellaria
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Class Trematoda (& Monogenea)
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Class Cestoidea (formerly Cestoda)
Classification
Class Turbellaria – Planaria
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exhibit regeneration
carnivorous (extensible pharynx)
free-living, nocturnal
fresh water
monoecious
locomote via ventral cilia and gland cells
(slime)
largest to locomote with cilia
A Planarian
Classification
Class Trematoda (& Monogenea)
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Fasciola hepatica- sheep liver fluke
Clororchis sinensis – human liver fluke
Schistosoma – blood flukes that inhabit veins of
urinary tract
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all are parasitic
resemble planarians in structure – highly specialized
existence
special adhesive organs – suckers
complicated life cycles
infections can occur from poorly cooked fish & shellfish,
and unclean water or skin
Fluke
Life Cycle
Classification
Class Cestoidea (formerly Cestoda)
Taenia (beef tapeworm)
 highly specialized internal parasite
 aberrant (atypical) group
 show pseudometamerism – each tapeworm is
closer to being a colony of individuals rather
than one segmented organism
Classification
(figure 33.11 page 606)
Taenia pisiformis
 scolex (head) with hooks and suckers
 neck (immature proglottids)
 mature proglottids (sexually
reproductive)
 ripe or gravid proglottids (contain
zygotes)
 production of new proglottids is
strobilization
Tapeworm:
1) scolex
2) immature proglottids
3) mature proglottids
4) gravid proglottids
Grade Bilaterata
Subgrade Pseudocoelomata
Phylum Nematoda
General characteristics:
unsegmented roundworms
 triploblastic
 grossly polyphyletic phylum (8 phyla)
 complete digestive tract
 fluid-filled pseudocoel
 longitudinal muscles only produce a whipping
motion
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Phylum Nematoda
General characteristics:
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worldwide distribution – cosmopolitan
terrestrial & aquatic
712,000 species
free-living & parasitic
varied nutrition: parasitic, carnivorous,
herbivorous, saprophytic
Phylum Nematoda
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A spade full of garden soil
contains about 1 million
nematodes.
Phylum Nematoda
• epidermis w/ cuticle
• mesoderm
• digestive tract
• gastrodermis
• fluid-filled pseudocoel
l.s. of a typical nematode
Nematoda
Phylum Nematoda
Ascaris lumbroides
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200,000 eggs per day
parasitic intestinal roundworm
ova are ingested due to poor sanitation
dioecious
cuticle – noncellular & secreted by
epidermis; impermeable to toxic
compounds & digestive enzymes
sexually dimorphic
Phylum Nematoda
Enterobius vermicularis
pin worm (anal worm)
 female worms migrate from the colon to anal
area at night to lay their eggs
 nervousness, scratching, reinfection
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Phylum Nematoda
Necator americanus
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hook worm
male has hook-shaped body w/cutting plates
on mouth that cut through the mucosa of
the intestine
secrete an anticoaggulant to prevent
clotting
larvum can burrow through soles of feet
Phylum Nematoda
Trichinella spiralis
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Trichina worm
causes trichinosis
Eating poorly cooked meat
Larva become encapsulated in skeletal
muscle (also in tongue) wherever there is a
rich blood supply
Parasitic
Nematode:
Trichinella
Phylum Nematoda
Loa loa
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eye worm
Vector – mango fly
Wanders in sub dermal connective
tissue (eyes, tongue, scrotum)
Africa
Phylum Nematoda
Wucheria bancrofti
Filarial worm
Mosquito vector
Larval stages in human blood
 Mosquito picks up microfilaria in taking
blood meal then larvae migrate to thoracic
muscles of mosquito, grow and migrate to
mouth parts
 Mosquito bites human, microfilariae
migrate to lymphatic system, mature
causing blockage
 Elephantiasis
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Phylum Rotifera
General characteristics:
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“wheel animals”
(cilia around mouth resembles a wheel)
freshwater
dieocious
some exhibit parthenogenesis
size of protozoan but multicellular
Phylum Rotifera
Unique characteristic:
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exhibit “cell constancy”
each species composed of members
possessing exactly the same number
of cells; cell division ceases with
embryonic development; no growth
or repair
Rofiter
Subgrade Coelomata
Phylum Annelida
General characteristics:
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Segmented worms
True coelom
More specialized systems
Show metamerism = true segmentation
(characteristic of higher animals)
Organs are paired in segments
Subgrade Coelomata
Phylum Annelida
General characteristics:
segmented arrangements of circulatory,
excretory, nervous, muscular, and
reproductive systems
 fluid-filled coelom = hydrostatic
skeleton
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Phylum Annelida
General characteristics:
triploblastic
 ventral nerve cord
 complete digestive tract
 worldwide distribution (cosmopolitan)
 trochophore larvum – very similar to mollusk
and flatworm larvum; on this basis, annelids
are thought to have evolved from a common
flatworm type ancestor
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Phylum Annelida
General Body Plan
• ectoderm
• mesoderm
• endoderm
• coelom
one metamere
• septum
l.s. segmented worm
Phylum Annelida: Classes
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Oligochaeta (oligo = few; chaeta = bristles)
– earthworms
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Polychaeta (poly = many; chaeta = bristles)
– sandworms (Neries)
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Hirudinea
– leeches
Phylum Annelida
Class Oligochaeta
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Darwin estimated that 1 acre
of farmland possessed about
50,000 earthworms which
produce about 15-18 tons of
castings per year
Phylum Annelida
Class Oligochaeta
General characteristics:
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few setae per segment
term “earthworm” is academically incorrect
because aquatic & parasitic forms are
included
most are monoecious, cross-fertilization
most highly organized animals to have
regeneration
clitellum (secretes cocoon)
Lumbricus
Anatomy
of
an
Annelid
Phylum Annelida
Class Polychaeta
General Characteristics:
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have numerous setae at ends of
parapodia
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parapodia – fleshy segmented
appendages for locomotion &
breathing
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Neries – sandworm
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tube worms
Polychaeta: Neries
Polychaeta:
Christmas Tree Worm
Phylum Annelida
Class Hirudinea
General Characteristics:
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mostly fluid feeders
fresh & marine
possess clitellum – apparent only during reproduction
have annelid characteristics but lack setae
true bloodsuckers have cutting plates for cutting through
tissue of the host organism
Hirudo medicinalis – medicinal leech
usually attaches by posterior sucker until suitable spot is
found for attachment of anterior sucker
salivary glands secrete anticoagulant called hirudin that
prevents clotting
Hirudinea: leech
Phylum Annelida
Class Hirudinea
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