Question

name
section
chapter
8
questions for review
1 complete summary table a - 1 in the appendix, filling in the characteristics of cnidarians in the appropriate row.
2 what specialized cells in hydra aid in capturing and subduing prey?
3 what structures determine whether a polyp of obelia is a hydranth (feeding polyp) or a gonangium (reproductive polyp)?
4 speculate about the selective advantage of radial symmetry and a diffuse nerve net for sessile and free - floating animals such as sea anemones and jellyfish.
5 what modification do sea anemones possess that allows food and water to be distributed among the partitioned regions of their bodies?
6 what modification do sea anemones possess to increase their digestive surface area?
7 match the phylum and class with the correct organism or characteristic.
hydra\ta. phylum cnidaria, class hydrozoa
obelia\tb. phylum cnidaria, class scyphozoa
sea anemone\tc. phylum cnidaria, class anthozoa
jellyfish\td. phylum ctenophora
no medusa form; only polyp
comb jelly
medusa form dominant; polyp greatly reduced
both polyp and medusa forms
lacks cnidocytes
chapter 8 ctenophores and cnidarians 145

Explanation:

1. Refer to the Appendix table for cnidarian characteristics.
2. Nematocysts in Hydra are specialized cells for prey - capture.
3. Feeding polyps (hydranths) have tentacles for feeding, while reproductive polyps (gonangia) produce medusae.
4. Radial symmetry allows 360 - degree sensing and response in sessile and free - floating animals, and a diffuse nerve net enables simple, rapid responses.
5. Sea anemones have septa that partition their bodies and allow food and water distribution.
6. Sea anemones have highly folded septa to increase digestive surface area.
7. Hydra: a. Phylum Cnidaria, class Hydrozoa; Obelia: a. Phylum Cnidaria, class Hydrozoa; sea anemone: c. Phylum Cnidaria, class Anthozoa; jellyfish: b. Phylum Cnidaria, class Scyphozoa; no medusa form, only polyp: c. (e.g., sea anemones in Anthozoa); comb jelly: d. Phylum Ctenophora; medusa form dominant, polyp greatly reduced: b. (e.g., jellyfish); both polyp and medusa forms: a. (e.g., Obelia); lacks cnidocytes: d. (Ctenophores lack cnidocytes).

Answer:

1. Refer to Appendix table.
2. Nematocysts.
3. Tentacles (feeding polyps have them for feeding, reproductive polyps produce medusae).
4. Radial symmetry for 360 - degree sensing, diffuse nerve net for simple responses.
5. Septa.
6. Folded septa.
7. Hydra: a. Phylum Cnidaria, class Hydrozoa

Obelia: a. Phylum Cnidaria, class Hydrozoa
sea anemone: c. Phylum Cnidaria, class Anthozoa
jellyfish: b. Phylum Cnidaria, class Scyphozoa
no medusa form, only polyp: c
comb jelly: d
medusa form dominant, polyp greatly reduced: b
both polyp and medusa forms: a
lacks cnidocytes: d