Activating Strategy
• List the types of waste products that animals
create.
• How does an animal regulate these?
AP Lesson #81
EQ: How do animals work to maintain
water balance and nitrogen removal?
What is osmoregulation?
• regulates solute concentrations
and balances the gain and loss
of water
hypotonic
– freshwater
• hypotonic
– saltwater
• hypertonic
– land
hypertonic
• dry environment
Why do all land animals have to conserve water?
always lose water (breathing & waste)
may lose life while searching for water
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How do land animals osmoregulate?
• Land animals manage
water budgets by:
– Drinking water
– eating moist foods
– using metabolic water
• Anatomical features and
behaviors:
– Water storage (ex.
Camels)
– Layers of waxy coverings
(ex. Human skin)
– nocturnal life style
Fig. 44-6
Water
balance in a
kangaroo rat
(2 mL/day)
Ingested
in food (0.2)
Water
gain
(mL)
Water
balance in
a human
(2,500 mL/day)
Ingested
in food (750)
Ingested
in liquid
(1,500)
Derived from
metabolism (250)
Derived from
metabolism (1.8)
Feces (0.09)
Water
loss
(mL)
Urine
(0.45)
Evaporation (1.46)
Feces (100)
Urine
(1,500)
Evaporation (900)
How do animals create intracellular waste?
• Cellular Digestion!
– proteins = CHON → CO2 + H2O + N
– nucleic acids = CHOPN → CO2 + H2O + P + N
We
CANNOT
store N!
NH2 =
ammonia
H| O
||
N–C– C–OH
|
H
R
H
CO2 + H2O
2
What happens to the nitrogen from metabolic reactions?
• Ammonia (NH3)
– very toxic
– very soluble
– must dilute it & get rid of it… fast!
• How you get rid of nitrogenous wastes
depends on:
– who you are and where you live
aquatic
terrestrial
terrestrial egg layer
How does nitrogen leave the body?
• Aquatic organisms
– Ammonia = most toxic
• Terrestrial
– Urea = less toxic
• Terrestrial egg
layers
– uric acid = least toxic
How do freshwater animals dispose of nitrogen waste?
• Use surplus water to dilute ammonia
– need to excrete it as very dilute urine
– also diffuse ammonia gills or through any moist
membrane
• Reabsorb salts in kidneys or active transport
across gills
Predators track fish by sensing ammonia
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How do land animals dispose of nitrogen waste?
• Need to conserve water
– urea = larger molecule = less soluble = less toxic
• produced in liver
• Kidney
H
H
H
– filter solutes out of blood
– reabsorb H2O (+ any useful solutes)
– excrete waste
H
N
C
O
N
• urine = urea, salts, excess sugar & H2O
mammals
How do egg-laying land animals dispose of
nitrogen waste?
• Cannot get rid of waste in the egg
– uric acid = BIGGER = less soluble = less toxic
– Insoluble in water
• birds, reptiles, insects
What’s the deal with uric acid?
• Polymerized urea
– large molecule
– precipitates out of solution = solid
• doesn’t harm embryo in egg
– white dust in egg
• adults still excrete N waste as white paste
So that is why
most male
birds don’t
have a penis!
– no liquid waste = white bird “poop”!
– Chemically reacts copper and bronze
O
H
H
N
N
O
O
N
N
H
H
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Summarizing Strategy
• Create a graphic organizer for information
about the three different forms of nitrogen
wastes.
Nitrogen Waste
Assessment
• HW: Read Chapter 44.2 – 44.5 (pgs 960 –
972)
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