Question

table 8 - 3 anatomy of obelia
body form structure function
polyp hydranth (feeding polyp) polyp specialized for food acquisition
tentacles defense and prey capture
hypostome elevated mound of tissue that expands or contracts to regulate size of mouth opening
gonangium (reproductive polyp) polyp specialized for reproduction
medusa buds product of asexual reproduction; medusae will be released from the gonangium when mature and will produce either sperm or eggs, which fuse with the respective gamete forming a zygote that will develop into a new polyp
coenosarc common chamber within which extracellular digestion occurs; nutrients are distributed throughout organism
perisarc translucent outer covering of organism; serves protective function
medusa tentacles defense and prey capture
manubrium stalk of fleshy tissue that supports the mouth
mouth ingestion of food and egestion of indigestible particles
gonads organs for sexual reproduction: either testes or ovaries
2 now examine a w.m. slide of an obelia medusa using medium power. locate the following structures that are defined in table 8 - 3: tentacles, manubrium, and mouth. (fig. 8.11).
check your progress
2.1 list several ways in which obelia differs from hydra.
chapter 8 ctenophores and cnidarians 129

Explanation:

Obelia is a colonial hydrozoan while Hydra is solitary. Obelia has both polyp and medusa stages in its life - cycle, Hydra is mostly in polyp stage. Obelia has specialized reproductive polyps (gonangium), Hydra does not have such specialized reproductive polyps.

Answer:

1. Obelia is colonial, Hydra is solitary.
2. Obelia has both polyp and medusa stages in life - cycle, Hydra is mainly in polyp stage.
3. Obelia has specialized reproductive polyps (gonangium), Hydra lacks such specialized reproductive polyps.