Let’s Make Urine!

   Excretory System

Mrs. O'Donnell

Honors Biology - Normal West High School

Nitrogen wastes are a by product of protein metabolism (break down of proteins). Amino groups are removed from amino acids prior to energy conversion. The NH2 (amino group) combines with a hydrogen ion (proton) to form ammonia (NH3).
Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss. Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.

1.       Go to the following site and click on the “Invertebrate  Excretory Organs” http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEXCRET.html#Invertebrate%20Excretory%20Organs

a.       Read over the descriptions of the flatworm, earthworm and ant excretory system. From these descriptions, explain what Malphigian tubules are. 

b.      What is the nephridium?  What types of organisms have these tubules? 

c.       Some organisms like the sponge, starfish, jellyfish and the amoeba do not have excretory systems.  Do these organisms create waste?  If so, how is the waste removed from the organism?

2.      Go to the following site http://www.biology.com.  Click on chapter 32 and then activity 32.2.  Using the mouse, scroll over the body and determine the function of each of the following parts of the excretory system 

·        Kidneys: 

·        Ureters

·        Urinary bladder

·        Urethra

3.      After you know a little bit about the above organs, you need to find out exactly how a kidney creates urine.  The nephron is the functional unit of the kidney where the filtration of blood occurs.  Click on the next activity (32.2 page 2).  Using the pictures and explanations, try to explain in your own words, what is happening.

Filtration:

Reabsorption: 

Secretion: 

 Excretion:

4.      Since blood carries our waste, what vessels are responsible for bringing unfiltered blood to the kidney and what vessel takes the filtered blood away?

5.      Using the web site, your book or any other sources, label the excretory system and the nephron. 

6.      Go to the following sites to read about Kangaroo Rats -  
http://www.desertusa.com/aug96/du_krat.html


http://www.oaklandzoo.org/atoz/azrat.html

Read about the kangaroo rat and explain why scientists are fascinated with the excretory habits of this organism.

What does the length of the loop of Henle correspond to?  In other words, what factors influence the length of this tubule in various species?  Explain.

7.      Kidneys regulate the amount of water in our blood (osmoregulation) as they are filtering it.  Imagine a day in which you don’t consume a lot of fluid, describe how and why your urine would be different than a day in which you did consume a lot of fluid.

created 22 April 2005 by Karen Slabe