Basal Animals: Radiata: Phylum Cnidaria Flashcards
Phylum Cnidaria
The hydroids, jelly fish, sea anemones, corals
Characteristics of Cnidarias
- Includes colonial hydroids, freshwater hydra, jellyfish, sea nettles, sea anemones, coral
- Radial symmetry
- “tissue” level of organization
- diploblastic construction- two “true” cell layers: epidermis and gastrodermis (what is mesolamella?)
- Gelatinous bodies
- Nematocysts- “ stinging cells”
- Body cavity and digestive cavity one and the same (no excretory system, no circulatory system.
Classification of the cnidarias
Phylum Cnidaria
- Class hydrozoa- colonial hydroids, freshwater hydras
- class scyphozoa- “true” jellyfish
- class staurozoa- star jeliies
- class cuboza- box jellies, sea nettles
- class anthozoa- sea anemones, corals
Class hydrozoa
- hydractinia”fuzzy” hydroid on hermit crab shell
- ## phylum cnidaria: class hydrozoa: the “hydroids”
sexual reproduction in medusa:
“ Alteration of generations”
-First polyp- planula larva- fertilization- gametes- medusa
Obelia hydroid- colony of polyps
Asexual reproduction in polyp colony:
“ Alteration of generation”
polyp colony- reproductive individual- medusa buds- medusae
obelia “jelly” medusa individual
Hydra
” freshwater hydras”
green hydra- hydra viridis
Book on freshwater hydra
Abraham trenbley’s 1744
Physalia physalia
” Portuguese Man-of-war”
Millepora complanata
” fire coral”
Aurelia aurita
Moon jelly
Phylum Cnidaria: class scyphozoa- “true” jellyfish
pelagia
” pelagie jelly”
Phylum Cnidaria: Class staurozoa- star jellies
Craterolophus
Phylum Cnidaria: Class Cubozoa: the “box jellies” and “sea nettles”
Chironex fleckerii “sea nettle”
Phylum Cnidaria: Class Anthozoa
- All are polyps
- no medusae in the anthozoa
- polyps reproduce both asexually (by budding) and sexually (by making gametes)
Darwin’s hypothesis- Subsidence of land
- coral reefs form around island
- reef grwo upward as land mass subsides
- lagon
Testing darwin’s hypothesis
- they drilled to 1114 ft. and found only coral; considered results inconclusive
symbotic relationship between reef-building corals and zooxanthellae
- mutualism- both organism benefit
- zooxanthellae provide coral with sugars and O2
- corals provide zooxanthellae with C02 and nitrogen
- coral with zooxanthellae deposit calcium carbonate 2- 3x faster than corals without
Phylum Cnidaria: Class Anthozoa corals
- Elkhotn Coral
- Staghorn coral
Phylum Ctenophora
- The comb jellies
Characteristics of ctenophores
Similar to cnidarias
- Radial symmetry
- “Tissue” level of organization
- Diploblastic construction (two “true” cell layers)
- gelatinous bodies
Different from cnidarians:
- no nematocysts
- combs, eight rows arranged radially
