COMPARATIVE ANIMAL PHYSIOLOGY

FALL, 1995

HOUR TEST II

PART I: ESSAY. [40 points] Answer both. 20 points each.

1. The heat balance equation is usually put as a sum of all heat gains and losses experienced by an animal. These gains and losses should sum to zero over a twenty-four hour period. What are the major pathways of heat gain and loss? Why should they sum to zero? Pick any two major pathways and discuss (1) what physical factors influence the direction and rate of heat transfer, and (2) how animals take advantage of these factors to maximize or minimize heat transfer by the two pathways.

2. The two main mechanisms in urine formation are ultrafiltration and active pumping. Describe what is meant by each term, and how each contributes to urine formation. What are the main factors that influence the functioning of each mechanism? Using one invertebrate and one vertebrate example, illustrate the use of these two mechanisms by animals, discussing in each example how the factors you described are used (or compensated for) by the animal.

PART II. SHORT ANSWER. [40 points] Answer any eight. Each is worth 5 points.

1. Where is most of the water reabsorbed in the mammalian kidney?

2. Why is it reasonable that most marine teleosts lack glomeruli?

3. Differentiate between “freeze tolerance” and “freeze resistance”.

4. List (list only) five adaptations necessary for successful hibernation.

5. Why are tuna called “warm-blooded” fish?

6. What is meant by the “lower critical temperature” of an animal?

7. In Tolkien's “The Hobbit”, Bilbo almost stumps Gollum with the riddle

Alive without breath,

As cold as death,

Never thirsty, ever drinking,

All in mail, never clinking.

to which the answer is, of course, fish. Marine or freshwater? Why so?

8. How are fish chloride glands functionally analogous to bird salt glands?

9. How does ADH (antidiuretic hormone) regulate urine osmolarity and volume?

10. Why don’t terrestrial animals use ammonia to any significant extent as a nitrogenous excretory product?

Part III. Data analysis: (20 points)

Using the data provided in the figure below, answer the question asked.

The above figure shows the activity of the sodium-potassium ATPase pump extracted from the brains of hamsters hibernating at different temperatures relative to the activity of the same enzyme extracted from the brains of hamsters maintained at the same temperature but not hibernating. (D: Na-K-ATPase from hibernating animals; m: from non-hibernating animals).

Explain in your own words what the results show, and relate the results to the mechanisms of hibernation.