II. Phylum Cnidaria

Question 1

Phylum Cnidaria characteristics

Answer 1

Eumetazoa
Radial symmetry
Diploblastic, tissue organization (ectoderm, endoderm)
Cnidocytes - stinging cells unique to phyla
GVC - digestive system (gastrodermis)
Mesoglea - gelatinous matrix between tissues
Waste - diffusion of ammonia
Gas exchange - diffusion
Nervous system - netlike

Question 2

Basic structure

Answer 2

Epidermis from ectoderm
Gastrodermis from endoderm
Mesoglea between layers
Cnidocytes - epidermal or gastrodermal in origin (nematocysts), used for defense, feeding, and anchoring

Question 3

Body plans

Answer 3

Polyp - columnar shape, sessile, asexual, single or colonial
Medusa - jelly fish, free swimming, inverted bowl surrounded by tentacles, dioecious
Alternation of generation - some classes have 2 distinct generations (asexual polyp stage, sexual medusa stage), planula larva - free swimming ciliated larva similar to flatworm

Question 4

Gastrovascular cavity (GVC)

Answer 4

Single opening (mouth)
Lined with gastrodermis (simple digestive system)
Functions: digestion, gas exchange, waste removal, locomotion, reproduction

Question 5

Classes of Cnidaria

Answer 5

Hydrozoa
Scyphozoa
Cubazoa
Anthozoa

Question 6

Class Hydrozoa

Answer 6

Alternation of generations
Colonial
Most marine
Ex: hydra, obelia, physalia

Question 7

Class Scyphozoa (true jellyfish)

Answer 7

Medusa - dominant stage of life cycle

Ex: aurelia, rhizostoma

Question 8

Class Cubazoa (box jellyfish)

Answer 8

Strong stings
Polyp stage is inconspicuous or unknown
Ex: box jellyfish

Question 9

Class Anthozoa

Answer 9

No medusa stage
Largest class
Symbiotic algae
Ex: sea anemone, sea pen, corals