Transcript Cnidarians - Cobb Learning

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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
predators
Have tentacles- stinging cells
(cnidocyts) , nematocysts
“thread cells” used as barbs
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
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: mouth, GVC
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
Sexually: usually in
medusa form, sperm and
eggs are released into
water
 (fertilized egg zygote
planula 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
(missing mesoderm)
› gastrovascular cavity (endoderm)
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1.
Hydrozoa
2. Scyphozoa
3. Anthozoa
Freshwater & marine.
 Medusa and polyp colonies
which appear to be one
organism different types of polyps work
together to serve the entire
colony
 Ex: Hydra, Obelia, Gonionemus
Physalia (portuguese-man-of-war)
36:40 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 anemones,
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
 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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1. Cnidarians are diploblastic, what does this mean?
2. What is the mesoglea?
3. How are Hydrozoans different from other classes of
cnidarians?
4. List examples of Hydrozoans.
5. What are scyphozoans, do they have a polyp
stage?
6. Anthozoans are known as the ______________
animals. Give examples of anthozoans.
7. What is an anthozoan’s protective skeleton made
of?
8. Why are coral reefs important?
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