1.  The osmoregulation and ion regulation problems of a freshwater fish are exactly the opposite of those facing a saltwater fish. What are the problems facing each and what are the physical reasons that fish (or many invertebrates) in the two environments face opposite problems?

2.  Some invertebrates approach the osmotic problems presented by the marine environment very differently than a teleost fish while others approach them in basically the same way. What do I mean by this and what are the terms for these distinct strategies?

3.  Related to these problems, why do sea birds need a salt gland and sharks a rectal gland? What problem are these structures designed to cope with? Thinking about this, explain why a shark has basically the same problem with ion regulation that a salt water bony fish does, but not the same water regulation problems (osmoregulation).

4.  What basic characteristic or pattern distinguishes mammals from other terrestrial vertebrates in terms of nitrogenous waste disposal? Why is this important for mammalian success in terrestrial environments? What specialization of the mammalian kidney allows this? How so?

5.  Why does the breakdown of nucleic acids and proteins pose a problem for animals? How do animals deal with this problem and how are their ‘solutions’ affected by both the environment they live in and phylogenetic relationships? Think in terms of specific forms that waste products take and what the costs and benefits of each are to an animal that forms or uses these. Put another way for one group: why are bird droppings so difficult to get off your windshield?

6.  Related to the last question, what is gout and why is it perhaps not surprising that the T. rex nicknamed ‘Sue’ who made the news last year appeared to suffer from it?

7.  Here’s a question that we did in class and that proved difficult. Look at it again, pick the right answer and explain why the others are not correct. All of the following are functions of the mammalian kidney EXCEPT:

• water retention
• filtration of blood
• excretion of nitrogenous waste
• regulation of salt balance in the blood
• production of urea as a waste product of protein catabolism

8.  Explain why can we describe the excretory process for nitrogenous wastes in vertebrates and many other animals as basically "indiscriminate filtration followed by selective reabsorption"?

9.  What are the specialized nitrogenous waste excretion structures of insects? Why might you expect a filtration-based system such as is found in vertebrates to be less effective for an insect?