phylum cnidaria: “ stinging cell ” hollow gut- (coel) on earth- since 670 mya radial symmetry...
TRANSCRIPT
Cnidarians 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: One body opening (mouth)
for food to enter and wastes to exit
Gastrovascular cavity: interior cavity where food is digested & nutrients are circulated around the body
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-10.html
Without Body Systems, how do they survive?
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
Cnidarians: Body Forms
Polyp: body with tentacles facing upward, sessile
Ex: hydra, sea anenome video polyp predation
Medusa: body with tentacles hanging downward, motile
Ex: jellyfish
Cnidarian Reproduction Asexually: by budding
Sexually: usually in medusa form, sperm and eggs are released into water
(fertilized egg zygote planula larvaadult)
Thousands of gametes are released at a time
Alternation of Generations:Video: medusa releasing from polyp
Checkpoint:1. List 5 traits that cnidarians share.2. How many germ layers do cnidarians
have? ____ Which are they missing?3. Are all cnidarians predators? Motile?4. Describe the specialized cells they
have on their tentacles.5. Describe how a cnidarian consumes
and digests food.6. Describe the two body forms
Cnidarians display, and give examples of each type.
basal disc: sticky structure at the bottom of polyp ; sessile
Epidermis
Mesoglea
Gastroderm
MesogleaGastrovascular cavity
Mouth/anus
Tentacles
Tentacles
Mouth/anus
Gastrovascularcavity
Polyp
Medusa
Structure:The Polyp and Medusa Stages
Diploblastic - 2 germ layers
› Epidermis - outer covering (ectoderm)› Mesoglea - middle non-living jelly-like
layer (missing mesoderm)› gastrovascular cavity (endoderm)
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Classes of Cnidarians
1. Hydrozoa
2. Scyphozoa
3. Anthozoa
Class Hydrozoa 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, GonionemusPhysalia (portuguese-man-of-war)36:40 Ocean Drifters
Asexual repro.-budding. Sexual repro. via gametes
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Class Scyphozoa 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 jellyfish12
Class Anthozoa ANTHO=“flower” All polyps-Medusa
stage absent Solitary or colonial Some produce
protective skeletons
All Marine Ex. Sea anemones,
corals 13
Class AnthozoaSea Anemone
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Video jewel anenome
Class AnthozoaMetridiumClass AnthozoaMetridium
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MouthMouth
TentaclesTentacles
PharynxPharynx
SeptumSeptum
Gastrovascular cavityGastrovascular cavity
Class AnthozoaCorals
Protective skeleton of calcium carbonate
Polyp retracts when not feeding
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Coral Reefs 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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Coral Reef Ecosystem
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photo © McGraw-Hill Higher Education, Barry Barker, Photographer
Cnidarian Cladogram
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AnthozoaScyphozoa Cubozoa
Hydrozoa
Radial symmetry, cnidocytes, planula larva
Septa divide gastrovascular cavity
Medusa cuboidal
Polyp stage reduced
Loss of medusa
Checkpoint
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?