Transcript Cnidarians

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Phylum Cnidaria: “stinging
cell”
Hollow gut- (coel)
On earth- since 670 MYA
radial symmetry
Germ Layers: 2
epidermal (ectoderm)
gastrodermal (endoderm)
NO ORGAN SYSTEMS
Segmentation: none
Movement: sessile or motile
Have tentacles- stinging cells
(cnidocyts) found on tentacles
Structures:
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One body opening (mouth) for
food to enter and wastes to exit
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Gastrovascular cavity: interior
cavity where food is digested &
nutrients are circulated around
the body
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Nerve net: net of nerves that
allow impulses to travel around
the body, senses the
environment
NEMATOCYSTS thread cells used
to capture prey (attach like
barbs)
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Label the hydra on
your notes!
http://www.arkive.org/common-jellyfish/aurelia-aurita/video-
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Nervous: Cephalization absent; Nerve
Net-conducts impulses
Skeleton: Hydrostatic- water pressure
maintains shape
Respiration: Oxygen diffuses into body
from water
Digestion: one body opening for food &
wastes
Excretion: simple diffusion into water
Circulation: GVC- gastrovascular
cavity
Reproduction: asexual and sexual,
alternation of generations
Polyp: body with
tentacles facing upward,
sessile
 Ex: hydra, sea anenome
 video polyp predation
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Medusa: body with
tentacles hanging
downward, motile
 Ex: jellyfish
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Asexually: by budding
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Sexually: in medusa form
only, sperm and eggs are
released into water
(fertilized egg
zygotelarvaadult)
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Thousands of gametes
are released at a time
Video: medusa releasing from polyp
Epidermis
Mesoglea
Gastroderm
Tentacles
Mesoglea
Gastrovascular cavity
Mouth/anus
Mouth/anus
Gastrovascular
cavity
Tentacles
Medusa
Polyp
basal disc: sticky structure at the
bottom of polyp ; sessile
› Epidermis - outer covering (ectoderm)
› Mesoglea - middle non-living jelly-like
layer
› gastrovascular cavity (endoderm)
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1.
Hydrozoa:fresh water and marine, polyp and medusa
present ex. Hydra, man-o-war, Obelia
2. Scyphozoans: cup- large jellyfish ex. box
3. Anthozoans: flower -all marine -polyps only
Ex: corals, sea anemone
Riches of the sea
Freshwater & marine.
 Medusa and polyp colonies which
appear to be one organismdifferent types of polyps work
together to serve the entire
colony
 Ex: Hydra, Obelia, Gonionemus
Physalia (portuguese-man-of-war)
37:40 Ocean Drifters
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Asexual repro.-budding.
Sexual repro. via gametes
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Scyph= “cup”
Large- Tentacles up
to 70 meters in
length
All marine
Independent
medusa forms
Lack polyp stage or
have for a very short
time
Ex. Box jellyfish
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 ANTHO=“flower”
 All
polyps-Medusa
stage absent
 Solitary or colonial
 Some produce
protective skeletons
 All Marine
 Ex. Sea anenomes,
corals
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Video jewel
anenome
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Tentacles
Mouth
Pharynx
Septum
Gastrovascular cavity
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Protective skeleton
of calcium
carbonate
 Polyp retracts when
not feeding
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Formed over thousands of
years from successive layers
of coral skeleton deposits
(calcium carbonate forms
underwater mountains of
coral animal skeletons)
 The underwater equivalent of
the amazon jungle- very high
species diversity and biomass
 Reefs contain sponges,
colonial hydrozoans,
anemones, many varieties of
coral, fish, many types of
worms we’ve not discussed,
not to mention bryozoans,
ctenophores, protists,
bacteria, etc etc..
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Coral Reef Ecosystem
Photo © McGraw-Hill Higher Education, Barry Barker, Photographer
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Anthozoa
Scyphozoa Cubozoa
Hydrozoa
Medusa cuboidal
Loss of medusa
Polyp stage
reduced
Septa divide
gastrovascular
cavity
Radial symmetry,
cnidocytes, planula
larva
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