Cnidarians. (Coelenterates). Phylum Cnidaria (Coelenterata). Class Hydrozoa = Hydra POLYP body form = “vase shaped” ; sessile Most live in colonies. 1 of 3 classes within Phylum Cnidaria. Phylum Cnidaria (Coelenterata). Class Scyphozoa: “Cup Animals”
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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
Phylum Cnidaria (Coelenterata) • Class Scyphozoa: “Cup Animals” • Medusa body form (bell-shaped); swimming • Commonly known as jellyfish • “Portuguese Man-o-war” • 200 different species
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
Classification • Common Name: Hydra • Scientific Name: Hydra • Phylum: Cnidaria • Class: Hydrozoa • Other: Phylum Coelenterata (Old name)
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 likestinging cells; neurotoxins cause paralysis
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
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)
Life Support Processes • Support: tissue layers, hydroskeleton
Ecological Relationships • Freshwater living • Solitary - not colonial like most hydrozoans • Carnivorous - predatory lifestyle
Body Systems Compared With Humans • Tissues - layers like our skin
Advancements Over the Previous Phylum • Nervous Structure • Movement • Active Feeding
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.
Preventing beach erosion Coral Reefs can be visible from the air!