phylum cnidaria general characteristics: – cnidarian means “stinging creature.” – radial...
TRANSCRIPT
Phylum Cnidaria• General Characteristics:
– Cnidarian means “stinging creature.”– Radial symmetry – Two different body plans exist:
• medusa and polyp – Cnidarians are made up of two tissue layers separated by mesoglea.
• Habitat: aquatic
Phylum Cnidaria• Nutrition: Capture pray using cnidocytes (stinging cells).– Sting prey and paralyze it so that it can be pulled into the
mouth to be digested.– Some organisms become immune to the sting and form
mutualistic relationships with cnidarians.
Phylum Cnidaria• Digestion: takes place in the gastrovascular cavity, a digestive
chamber with one opening, food enters here.– Break down occurs in the cavity and then partially
digested food is absorbed by the gastroderm and digestion is finished intracelluarly.
Phylum Cnidaria• Circulation: takes place through diffusion in the
gastrovascular cavity• Respiration: Diffusion of oxygen and carbon dioxide takes
place in the gastrovascular cavity.• Excretion: diffusion through the body wall or exits out
through the mouth of the organism.
Phylum Cnidaria
• Nervous: – Touch sensitive stinging cells
called nematocysts– a nerve net, but no brain– statocysts used to detect
gravity– ocelli to detect light
(eyespots)
Phylum Cnidaria
• Reproduction:– Sexual reproduction occurs through external fertilization
when the sperm is united with an egg outside of the body
Phylum Cnidaria
• Reproduction: – Asexual reproduction can occur through budding and
fission.
Phylum Cnidaria• Examples: sea anemones and coral have a dominant polyp
stage, hydra alternate between forms, jellyfish and sea wasps (box jelly) with a dominant medusa form