Cnidarians

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Cnidarians

• (Coelenterates)

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Phylum Cnidaria (Coelenterata)

• Class Hydrozoa Hydra
• POLYP body form vase shaped sessile
• Most live in colonies.

1 of 3 classes within Phylum Cnidaria
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Phylum Cnidaria (Coelenterata)

• Class Scyphozoa Cup Animals
• Medusa body form (bell-shaped) swimming
• Commonly known as jellyfish
• Portuguese Man-o-war
• 200 different species

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Phylum Cnidaria (Coelenterata)

• Class Anthozoa Flower Animals
• 6,100 different species
• Sea Anemones, Corals
• Coral Reef 30 degrees North or South of the
  equator, shallow water for photosynthetic algae
  that live in symbiosis with coral

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Classification

• Common Name Hydra
• Scientific Name Hydra
• Phylum Cnidaria
• Class Hydrozoa
• Other Phylum Coelenterata (Old name)

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Major Characteristics

• Body Plan Hollow, 2 layered sac
• Body Cavity Endoderm, Mesoglea (jelly like),
  Ectoderm
• Symmetry Radial - pull in food from all around
• Cell Specialization No Organs, Nematocysts
  harpoon like stinging cells neurotoxins cause
  paralysis

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Life Support Processes

• Absorption Gastroderm directly into the body
  wall
• Feeding tentacles pull food into the mouth
  they are carnivores
• Digestion Gastroderm (endoderm), food vacuoles
  in cells
• Respiration Circulation Gastrovascular inner
  cavity

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Life Support Processes

• Excretion Mouth opening, diffusion
• Secretion sticky base for attachment
• Response Nerve Net - contractile fibers in the
  epidermis Ocelli - detects light
• Movement contractile fibers tumble motion
  through the water
• Reproduction Asexual budding sexual
  hermaphrodite (no self fertilization)

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Life Support Processes

• Support tissue layers, hydroskeleton

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Ecological Relationships

• Freshwater living
• Solitary - not colonial like most hydrozoans
• Carnivorous - predatory lifestyle

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Body Systems Compared With Humans

• Tissues - layers like our skin

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Advancements Over the Previous Phylum

• Nervous Structure
• Movement
• Active Feeding

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Diagram of Hydra
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Noteworthy Cnidarians!

• The largest jellyfish is the Arctic Giant
  Jellyfish it can have a diameter over 8 ft. with
  tentacles stretching as long as 120 ft.
• The most venomous jellyfish is the Australian Sea
  Wasp death can occur within 1-3 minutes.
• The Great Barrier Reef is the worlds largest
  stony coral structure stretching for 1,260 miles
  off Northeast Australia.

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Lions Mane Jellyfish
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Preventing beach erosion
Coral Reefs can be visible from the air!
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Great Barrier Reef - Australia