A Guide for the Study of Animals Part 22

Identify your specimens. Then study as many as your time will allow, using these general questions for each:--

_Questions._

1. How large is the specimen and what is its shape?

2. Can you distinguish a head or a head end? If so, by what peculiarities?

3. State whether the body is segmented or not, and, if it is, whether the segments are alike in form and appearance, _i.e._ whether the segments are uniform.

4. State whether the animal is bilaterally symmetrical, radially symmetrical, or without symmetry.

5. Compare this worm with the earthworm as to sense organs.

6. What organs for respiration has it?

7. What special protective devices has it?

8. If possible, find out and state where this worm lives. What can you see in the structure of this worm which enables it to live where it does?

Summary of the Comparative Study of Worms

1. Name the different worms you have studied. What characteristics have they in common?

2. What different methods of obtaining food do they show?

3. What variations do they show in senses? in sense organs?

4. Which one seems to you best adapted to its habitat? In what ways?

_Suggested drawings._

a. One drawing of each worm studied.

Review and Library Work on Worms

1. What are the distinguis.h.i.+ng characteristics of worms?

2. Give the cla.s.ses of worms, and the authority for this cla.s.sification.

3. What kind of soil do earthworms seem to prefer? Why should they?

How do they form their burrows? What are the castings around the mouth of a burrow? How are they placed there?

4. In what ways do earthworms benefit the soil? How great is their effect estimated to be?

5. Give a brief sketch of the life of Charles Darwin, noting especially the work he did with earthworms.

Why is Darwin's work on earthworms noteworthy: because it is such a large proportion of the work he did, or because it is so much of the work which has been done on earthworms?

6. How are earthworms protected against the cold of our winters? What limits the northern range of earthworms?

7. Where are earthworms found geographically? Why are they so widely distributed? By what means are they extended from one locality to another?

8. How do earthworms reproduce? What care do they take of their young?

9. What tissues or organs of earthworms correspond in function with the ectoderm of hydra; with the endoderm? Why does an earthworm need a system of blood circulation more than a hydra does?

10. Contrast the number of openings in an earthworm's alimentary ca.n.a.l with the number in a hydra's digestive cavity. Which plan seems a better one? In what respects?

11. Contrast a cross section of hydra with one of earthworm as to the number of cavities. Which seems to you the better plan? Why?

12. Why does a nereis need more respiratory surface than an earthworm does?

13. Comparing earthworm and nereis, in what respects is the earthworm degenerate? How does it manage to succeed so well with such a degenerate body?

14. What is a parasite? How many hosts does a typical parasite require for its development? Which host is known as the intermediate one?

15. Trace the history of a tapeworm from the egg to the adult. At what stage are they most likely to be destroyed? What provision is there for this? What advantages are there to the host in the fact that a tapeworm's egg cannot develop in the original host? What advantages to the parasite?

16. What organs has a parasite lost, if it ever had them? How does it succeed without them? What connection is there between parasitism and degeneration? Can you decide which is cause and which is effect? If so, which is?

17. Why do worms so easily become parasitic? What advantages are there in becoming a parasite? What disadvantages?

18. What is radial symmetry? Name two animals which show it. What is bilateral symmetry? Name two animals which show it. What is the relation between locomotion and symmetry?

19. What is meant in biology by the term "regeneration?" To what extent have we this power? To what extent have hydra and earthworm?

What are the results of this power?

20. Name various methods of locomotion among worms. Give examples.

Name a fixed or sedentary worm.

21. What is the economic importance of worms? Consider here not only earthworms and tapeworms, but also the stomach worms of sheep, liver flukes, trichinae, hookworms, vinegar eels, and as many others as you have time and books to look up.

5. THE CONNECTION BETWEEN STRUCTURE AND FUNCTION

_A Review of the Work done on the First Four Groups of Animals_

Review all your studies on the protozoa, sponges, clenterates, and worms. Write the results in the following summary:--

1. What work, _i.e._ labor, must an animal do to live?