Transcript 27-4 Excretion PowerPoint

Lesson Overview
Excretion
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Lesson Overview
27.4 Excretion
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Lesson Overview
Excretion
THINK ABOUT IT
In addition to carbon dioxide and indigestible material, animals generate
other wastes that are released into body fluids and that must be
eliminated from the body.
What are these wastes and how do animals get rid of them?
Lesson Overview
Excretion
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The Ammonia Problem
The breakdown of proteins by cells releases ammonia.
Ammonia is poisonous & kill most cells.
The elimination of ammonia is called excretion.
Some small animals that live in water rid their bodies of ammonia across their skin.
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Most larger animals have excretory systems that process ammonia and eliminate it
from the body.
Lesson Overview
Excretion
Storing Nitrogenous Wastes
Animals that cannot dispose of ammonia continuously, so they evolved
ways to store nitrogenous wastes
Ammonia cannot be stored in body fluids = too toxic.
Insects, reptiles, & birds (egg layers) convert ammonia into a sticky
white compound -uric acid, less toxic than ammonia and less soluble in
water.
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Lesson Overview
Excretion
Storing Nitrogenous Wastes
Mammals and some amphibians convert ammonia to a different
nitrogenous compound—urea.
Urea is less toxic than ammonia, but unlike uric acid, it is highly soluble
in water.
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Lesson Overview
Excretion
Maintaining Water Balance
Excretory systems are important in maintaining the proper balance of
water in blood & body tissues.
Desert animals eliminate things differently that animals in a pond
Many animals use kidneys to separate wastes &excess water from
blood to form a fluid called urine.
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Lesson Overview
Excretion
Maintaining Water Balance
Kidneys separate water from waste products.
Kidney cells pump ions from salt to create osmotic gradients.
Water then “follows” those ions passively by osmosis.
Kidneys, however, usually cannot excrete excess salt.
Lesson Overview
Excretion
The Ammonia Problem
How do animals manage toxic nitrogenous waste?
Lesson Overview
Excretion
The Ammonia Problem
How do animals manage toxic nitrogenous waste?
Animals either eliminate ammonia from the body quickly or convert it into
other nitrogenous compounds that are less toxic.
Lesson Overview
Excretion
Freshwater Animals
Many freshwater invertebrates lose ammonia to their environment by
diffusion across their skin.
Many freshwater fishes and amphibians eliminate ammonia by diffusion
across the gills.
Lesson Overview
Excretion
Freshwater Animals
Water moves into their bodies across
the gills.
Salt diffuses out.
If they didn’t excrete water, they’d
look like water balloons with eyes!
Freshwater fish excrete water through
kidneys that produce lots of watery
urine.
They don't drink, and they actively
pump salt in across their gills.
Lesson Overview
Excretion
Freshwater Animals
Other examples of Excretion of Freshwater animals:
Flame Cells-flatworms have specialized cells
The excess water travels through excretory tubules and leaves through
pores in the skin.
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Lesson Overview
Excretion
Saltwater Animals
Marine invertebrates have body
fluids with water concentrations
similar to that of the seawater
around them.
The bodies of some saltwater
fishes, contain a lower
concentration of salt than the water
Saltwater fish lose water through
osmosis, & salt diffuses in.
Lesson Overview
Excretion
Saltwater Animals
Saltwater fish conserve water by
producing very little concentrated
urine.
They drink, and they actively pump
salt out across their gills.
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Lesson Overview
Excretion
Excretion in Aquatic Animals
How do aquatic animals eliminate wastes?
Lesson Overview
Excretion
Excretion in Aquatic Animals
How do aquatic animals eliminate wastes?
In general, aquatic animals can allow ammonia to diffuse out of their
bodies into surrounding water, which dilutes the ammonia and carries it
away.
Lesson Overview
Excretion
Excretion in Terrestrial Animals
In dry environments, land animals can lose large amounts of water from
respiratory membranes that must be kept moist.
In addition, they must eliminate nitrogenous wastes in ways that require
disposing of water—even though they may not be able to drink water.
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Lesson Overview
Excretion
Terrestrial Invertebrates
Some terrestrial invertebrates, including annelids and mollusks, produce
urine in nephridia.
Nephridia are tubelike excretory structures that filter body fluid.
Body fluid enters the nephridia through openings called nephrostomes
and becomes more concentrated as it moves along the tubes.
Urine leaves the body through excretory pores.
Lesson Overview
Excretion
Terrestrial Invertebrates
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Other terrestrial invertebrates, such as
insects and arachnids, convert ammonia
into uric acid.
Uric acid is absorbed from body fluids by
Malpighian tubules.
As water is absorbed from these wastes,
they form crystals that form a thick paste,
which leaves the body through the anus.
This paste contains little water, so this
process minimizes water loss.
Lesson Overview
Excretion
Terrestrial Vertebrates
In mammals and land amphibians,
ammonia is converted into urea, which
is excreted in urine by the kidneys.
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Lesson Overview
Excretion
Terrestrial Vertebrates
Reptiles and birds convert ammonia into uric acid, which is passed
through ducts into a cavity that also receives digestive wastes from
the gut.
The walls of this cavity absorb water from the wastes, causing the uric
acid to separate out as a thick, milky-white paste recognized as
“bird droppings.”
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Lesson Overview
Excretion
Adaptations to Extreme Environments
Most vertebrate kidneys cannot excrete concentrated salt.
Most vertebrates cannot survive by drinking seawater.
The extra salt would overwhelm the kidneys, & the animal would die of
dehydration.
Some marine reptiles & birds have evolved special adaptations to rid
themselves of excess salt.
The petrel (bird) has special glands in its nostrils that separate salt from
the water it swallows and excrete the salt as a thick, sticky fluid.
Petrel Salt Gland
Marine Iguana getting rid of salt
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Lesson Overview
Excretion
Adaptations to Extreme Environments
The kidneys of kangaroo rats, which live in the desert, produce urine
that is 25 times more concentrated than their blood!
In addition, their intestines are so good at absorbing water that their
feces are almost dry.
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Lesson Overview
Excretion
Excretion in Terrestrial Animals
How do land animals remove wastes while conserving water?
Lesson Overview
Excretion
Excretion in Terrestrial Animals
How do land animals remove wastes while conserving water?
Some terrestrial invertebrates, including annelids and mollusks, produce
urine in nephridia.
Lesson Overview
Excretion
Excretion in Terrestrial Animals
How do land animals remove wastes while conserving water?
Other terrestrial invertebrates, such as insects and arachnids, convert
ammonia into uric acid.
Mammals and land amphibians convert ammonia into urea, which is
excreted in urine. In most reptiles and birds, ammonia is converted into uric
acid.