Phylum Cnidaria Flashcards
what groups comprise the cnidarians?
- hydrozoans
- jellyfish
- sea anemones
- corals
characteristics of cnidarians
- marine
- cylindrical bodies
- possess tentacles
- blind gut (single mouth/anus)
- first organisms with true tissues
- nerve net
- acoelomates
- swim by beating rows of cilia
what kind of symmetry do cnidarians have?
radially symmetric
how many tissue layers do cnidarians have?
2 (diploblastic)
endoderm, ectoderm
what are the scyphozoa?
jellyfish (medusa stage)
what are the anthozoa?
corals, anemones, sea pens, sea fans (polyps)
what are the hydrozoa?
hydroids (polyps)
polyp stage
sessile (attached to a substrate)
juvenile
cylindrical with tentacles
mouth directed upward
medusa stage
adult, sexual
umbrella shaped free floating body type
mouth and tentacles pointed downward
what makes sea anemones different from other cnidarians?
their mouth leads to a pharynx and then the gastrovascular cavity (purpose is ingestion)
how do cnidarians catch prey?
tentacles around their mouth with stinging cells
-most cnidarians are carnivorous
cnidocytes
specialized cells that release barbed nematocysts which sting and inject toxins into prey
gastrovascular cavity
internal space in all cnidarians
- used for digestion
- only open at the mouth
what are the two tissues of sponges?
epidermis and gastrodermis (middle is lined with mesoglea)
