Download ANIMALIA - Sardis Secondary

ANIMALIA
CNIDARIA LAB
Purpose:
To observe similarities and differences between the different members of the Phylum Cnidaria.
Procedure:
1. Sketch Hydra bud & ovaries under low power. Label the basal disc, stalk, bud, ovary,
tentacles, mouth and cnidocytes.
2. Sketch Hydra C.S. or T.S. under medium or high power. Be sure to sketch the round
cross- section(c.s) one. Label the endoderm, ectoderm, gastrovascular cavity, gland
cells, and mesoglea.
3. Sketch Obelia colony under low power. Label the feeding polyp, reproductive polyp,
mouth, medusa bud, and tentacles.
4. Sketch the Aurelia medusa. Label the mouth, mouth lobes, tentacles, and gonads.
Observations:
The four (4) diagrams listed in the procedure. Include all parts mentioned above and the
apparent magnification.
Discussion:
Answer the following questions in full sentences.
1. Describe the structure and function of cnidocytes (stinging cells)? (2 marks)
2. What type of symmetry is exhibited by cnidarians? (1 mark)
3. How does the method by which cnidarians obtain food differ from the method by which
porifera obtain food? Include the structures or cell-types involved. (4 marks)
4. a) How does the method by which cnidarians digest food differ from the method by
which porifera digest food? Include the structures or cell-types involved. (4 marks)
b) Which system is more advanced? Why? (2 marks)
c) What is the advantage of this system? (2 marks)
5. Describe the differences in sexual reproduction between the Hydra and Aurelia medusa.
(2 marks)
6. Corals are another class of Cnidarians. Describe the significant roles they play in marine
ecosystems. (2 marks)
** See back for Conclusion**
Conclusion:
Answer the following questions together in paragraph form. Be sure to begin your conclusion
with a restatement of the purpose in your own words.
i.
ii.
iii.
In Greek mythology, Hydra was a monster with nine heads. Any head, when cut off,
was replaced by two others. How does this relate to the freshwater creature?
How does the polyp differ from a medusa? Include a discussion of motility,
reproduction, and body form for each.
Describe three (3) evolutionary developments that cnidarians have that enable them
to capture prey and move that prey into their mouths?