Phylum Cnidaria. General Characteristics About 9000 species Simple nervous system Called a nerve...
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Transcript of Phylum Cnidaria. General Characteristics About 9000 species Simple nervous system Called a nerve...
General Characteristics About 9000 species Simple nervous systemCalled a nerve net. No brainHas tentacles, sometimes very small
that grab prey and pull them to the mouth, thus they are predators.
They might be sessile or motile, or each at different times of their life.
General Characteristics Cont’d-• Either tubular or bell shaped(Polyp or medusa form)• Only animal with
cnidocytes• Cnidocytes-specialized
stinging cells (on tentacle)• All marine (aquatic) except For a few freshwater examples
____________________________
• Cnidarians’ bodies are organized around the (hollow stomach area)gastrovascular cavity, where digestion takes place• GV has a single opening that
serves as both mouth and anus
2 Layers of Cells
–Diploblastic means that its body developes from 2 layers of cells.–Gastrodermis: lines GV cavity–Epidermis: lines the outside of
the body (the skin)
Stinging Cells
• Have Cnidocytes which are cells that contain nematocysts: barbed thread-like structures inside the cnidocyte that shoots out and can puncture and poison or entangle prey
Feeding
• Using tentacles they touch the prey and inject the “poison” into them with nematocysts. This “stuns” or paralyzed the prey. WHY? So it wont tear its tentacles off in the struggle.• Inner gastrodermis secretes digestive juices into gastrovascular cavity which digests food and circulates nutrients
Nervous and Movement
•Have a nerve net & sensory receptors•Muscles help in directional movement & capturing prey
Life Cycles
• Cnidarians have two body forms that are representative of the sexual and asexual life cycles that they undergo.
–Polyp–Medusa
Polyp
–Usually attaches to a substrate at the aboral end (the end away from tentacles)–Oral end is surrounded by feeding
tentaclesUsually the asexual reproductive form
Medusa
Sexual Reproductive form (but hermaphroditic)
Shaped like an upside-down bowlTentacles surround the mouth that is
housed underneath the bell
• When cnidarians display both forms at some point in their lives, they are said to display dimorphism.
_________________________ Both sexual and asexual Sexual
Gametes (sperm and egg)released into water. Fertilization takes place to create free-swimming larvae
AsexualBy budding
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• Scyphozoa: Jellyfish
• Anthozoa: Sea anemones & Corals
• Hydrozoa: Hydra
• Cubozoa: Box Jellies
Includes hydras, fire corals, and Portuguese Man of War
Cubozoans• Similar to Scyphozoans, except that
their medusa is cuboidal• Includes the box jellyfish–1 of the 10 most venomous
animals on the planet
Class Anthozoa
• Polyps that are flower-like• Includes sea anemones, corals,
sea whips, and sea fans