Which of these animals correctly describe how its nitrogenous waste is related to its phylogeny and habitat?

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Which of these animals correctly describe how its
nitrogenous waste is related to its phylogeny and
habitat?
1. Because I live in water, I excrete urea, a
water soluble nitrogenous waste.
3. Living on land, I need to conserve as much
water as possible, so I excrete a solid
nitrogenous waste.
2. I need to stay light on my feet for speed, so
I excrete a solid nitrogenous waste.
4. My ancestors and I lay shelled eggs, so our
embryos are protected from harmful ammonia by
converting it to an insoluble precipitate.
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Regulating the Internal Environment
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Learning Objectives (2/25/09)

1. Discuss the challenges of excretion and
   osmoregulation for marine, freshwater and
   terrestrial organisms
2. Compare and contrast the variety of excretory
   systems in invertebrates
3. Explain the correlation between type of
   nitrogenous waste product with animal habitat
   and/or reproductive strategy
4. Describe examples of the relationship between
   structure and function in excretory systems (esp.
   the 4 key functions)
5. Discuss the intrinsic and extrinsic regulation of
   kidney function in water balance
6. Discuss the roles of the hypothalamus in
   vertebrate water budgets

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Most animal cells cannot survive a net gain or
loss of water
Tardigrades are generally less than ½ mm. They
have five body segments, four pairs of legs, and
each leg ends in a set of claws. Tardigrades have
a ventral nervous system with a brain and
eyespots. They have well developed excretory,
muscular, digestive, and reproductive systems. A
characteristic of the phylum is the lack of both
the circulatory and respiratory systems. They
breathe through their cuticle and have a hemocoel
for circulation.
For more info. visit http//www.jsu.edu/depart/bio
logy/tardy.htm
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Osmoregulation in Terrestrial Animals

1. Protective outer layers
2. Drinking fluids and eating moist foods
3. Behavioral adaptations
4. Adaptations to use metabolic water
5. Excretory adaptations

Fluid in which body compartment is being
regulated?
Describe how water may be gained and lost by
animals.
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The challenge of living in water for
osmoregulators
p. 936
Water is the physiological solvent, but how is
this volume regulated in most animals, no matter
what their environment? Which animals tend to be
osmoconformers, and where do they live?
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Is this a countercurrent mechanism? Is NaCl
excretion by active or passive transport? Do
marine animals have other mechanisms of
osmoregulation?
p. 939
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Nitrogenous waste is related to reproductive
strategy and habitat
Which of these animal groups excrete nitrogen
wastes dissolved in a watery solvent? Explain why.
See p. 943
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Key Functions in AnimalExcretory Systems

• Filtration
• Reabsorption
• Secretion
• Excretion
• Where does each process happen?
• What is the net direction of movement for each
  material?
• Is the movement of material by active or passive
  transport?

Intravenous Pyelogram (IVP)
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Protonephridia in Platyhelminthes

• Identify the fluid that is filtered at the flame
  bulb.
• What is the force that drives the production of
  fluid in the flame bulb system?
• Is the filtrate modified in the tubule? Explain.
• What other organ may function in excretion in
  these animals?
• How do these animals regain lost fluid?

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Metanephridia in Annelids

• Describe any advances over the protonephridial
  system.
• In which direction(s) are materials moving
  between the blood and the filtrate? by what
  mechanisms?
• How is this system similar to the mammalian
  nephron in structure and function? Explain.

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Malpighian tubules in Arthropods
p. 944

• The organs of excretion in arthropods function in
  both tubular secretion and tubular reabsorption.
  
• Where do these processes take place?
• How is this different than the same processes in
  the mammalian kidney?
• Contrast the function of the insect posterior
  alimentary canal with that of mammals.

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Mammalian Kidney
See p. 946
What is the rate-limiting step in urine
formation? Which renal mechanisms involve active
transport? Why does glucose sometimes appear in
the urine of diabetics?
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Juxtamedullary Nephron Function
What materials are initially filtered into the
tubule? How would a short loop of Henle affect
the ability of an animal to concentrate urine
(i.e. conserve water)? Name an alternative
water conservation adapatation. What is the
target tissue for the hormone ADH (a.k.a.
Vasopressin)?
See p. 949
Passive
Active
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Extrinsic Regulation of the Kidney
ADH is also known as Vasopressin. What is the
primary target tissue for this hormone? Name the
other action of this hormone, and describe how it
contributes to homeostasis. Describe the
communication between the hypothalamus and the
posterior pituitary. Why are aquaporins necessary?
See p. 953
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Renin-Angiotensin-Aldosterone System
Where is the receptor in this homeostatic
mechanism? Where is the effector? Is this
intrinsic or extrinsic regulation? What kind of
molecule is renin? (hormone, neurotransmitter,
enzyme, etc.) How does Aldosterone increase
sodium reabsorption at the kidneys?