AP Biology
Osmoregulation Worksheet
This worksheet approaches the subject of osmosis using evolution, homeostasis and regulation.
Use your knowledge of osmosis and your text (chapter 32 sec. 3) to describe how homeostasis is maintained in these
organisms using these features to survive. Use one or two sentences for each. Also, note whether each organism is
an osmoconformer or an osmoregulator. Which is more evolutionarily advanced?
1.
Kingdom Protista: paramecia (contractile vacuoles, fig. 5.12)
2.
Phylum: Platyhelminthes: planaria (flame cells or protonephridia, fig. 32.18)
3.
Phylum: Annelida: earthworms (nephridia, Google it)
4.
Phylum: Arthropoda: grasshoppers (malpighian tubules, p.656)
5.
Phylum Mammalia: lions (kidney/nephron, fig. 32.19)
Use your textbook to look up the structure of a nephron, the functional unit of a kidney. (Bio in Focus: Fig. 32.21)
6. Explain how the osmolarity of the kidney changes as the filtrate in the tubule moves from the cortex to the outer and inner
medulla.
7.
Describe how the nephron uses the osmolarity of the interstitial fluid in the kidney to reabsorb water back into the blood
stream by osmosis.
8.
How is the high osmolarity of the kidney maintained?
9.
The marine environment is strongly dehydrating due to the high salt concentration. Fish, like sharks, drink large amounts
of water and excrete ions and nitrogenous waste in urine that is low in volume and highly concentrated in urea
(hyperosmotic urine). How would fresh water fish maintain their water balance? fig. 32.15
10. Kangaroo rats live in the desert and get their water through the food they eat. A mammal with typical kidneys (like a
humans) would not be able to survive. How has the Loop of Henle adapted in kangaroo rats to give them the ability to
survive with so little water? p.661
11. Which hormone causes the body to conserve water? p.661
12. Are alcohol and caffeine diuretic or antidiuretic substances? (experience? Google it)
Mrs. Loyd 
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7/12/16
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