How To Study Living Animals


Homology of the Vertebrate Skeleton
Materials.

Prepared skeletons of an amphibian, a reptile, a bird, another mammal, and man herunterladen. If any of these be lacking, lantern-slide illustrations may be used in a partially darkened room.

Observations.

Having studied the frog’s skeleton in detail, the student can readily compare each of these types with it herunterladen. Compare in a very general way the skulls, the girdles, and the limbs; their form and use. Note variations in the form and number of the vertebræ and the number of the ribs microsoft office kostenlos downloaden vollversion deutsch chip.

Questions.

1. In which types of vertebrates are the joints between the skull bones bound with cartilage? How does the joining change in later types?

2. What dissimilarities occur in the series as regards closure or boxing in of the eye orbits, nostrils, and skull bones? How would these changes in joining and closure affect strength, rigidity, and protection?

3. What evidence is there that such improvement has affected brain capacity and intelligence?

4. State how the attachment of the skull to the vertebral column changes as the animal man assumes an erect position.

5. Are the vertebræ of these types alike in structure? What is the general form of an horizontally placed vertebra, as in the horse or a reptile, and of a vertically placed one, as in man? If you see any differences, account for them.

6. Wherever possible, find the vertebræ of the neck (cervical), and note the number of them in each case.

7. How is flexibility of the column accomplished in certain types or in certain places of one type? How is rigidity gained? State instances in each answer.

8. Examining the interior of the turtle’s “shell,” find out and explain how the vertebræ have been modified to form the upper “shell.” How has the under portion (plastron) been formed?

9. In round numbers, which skeleton has the greatest number of vertebræ and which the least?

10. Which skeleton has the greatest number of ribs, and which has the least?

11. In a summarizing statement explain any variations you find in the pectoral and pelvic girdle for strength (rigidity); flexibility. This answer may be written as a table, naming the bones, opposite each stating its condition, and then what it affords or is adapted to.

12. What is accomplished by having two bones in the shank of the leg? In what types or forms is there but one, and which one is it?

13. Can you assign any advantages in power, agility, length of leg, or position of leg and foot accruing from a long ankle? (See horse, frog, et al.)

14. Enumerate the types or forms, and opposite each state the number of fingers and toes.

15. Make a table, heading one column “Form or type”; another, “Habitat”; and a third, “Habit.” Judging from the structure which you see or from your previous knowledge or experience, fill in the table, stating whether the type is aquatic, terrestrial, or aërial; whether it burrows, walks, runs, or climbs, etc.

16. From your statements in 15, explain how the peculiar mode of life affects the structure of these types.


CHAPTER VII
ADAPTATIONS FOR THE PRESERVATION OF THE SPECIES

A. Methods of Reproduction