Animal homeostasis

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Animal homeostasis applies to single-celled and
complex organisms Metabolic activities require
input of oxygen, nutrients, salts, etc. Waste
products must be expelled Internal environment
responds to changes in external environment
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Complex organisms- organ systems how is this
coordinated? What systems actually interact
with the environment? Intake of metabolic
requirements Expulsion of waste Thermoregulation A
djustment of fluid levels
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Water and osmotic regulation Marine
invertebrates are in osmotic equilibrium with
their environment Osmotic conformers- as the
salinity of the water changes, so does
theirs Open sea- very stable environment Organism
s that live there dont tolerate change well
(stenohaline)
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Coasts, estuaries, etc.- conditions are
much more unstable and organisms must be able
to tolerate change Euryhalines- capable of
osmotic regulation shore crab-
hyperosmotic- internal salt concentration is
higher than that in the environment How?
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When water moves in, it can be excreted
by kidneys Salt loss- active transport by
specialized cells in gills to bring salt back
into body
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Osmotic regulation in fresh water organisms must
be very good at hyperosmotic regulation Protecti
ve covering on body Kidneys that remove excess
water Salt-absorbing cells Amphibians use skin
to reabsorb salt
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Marine bony fishes- hypoosmotic
regulation (internal salt concentration is lower
than that in water) Without regulation would
tend to lose water and gain salt Mechanisms d
rink seawater sodium chloride is secreted by
specialized cells in gills other salts are
excreted
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Sharks and rays raise osmolarity of blood by
conserving urea (osmolarity determined by total
ion concentration
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Salt and water balance in terrestrial
animals Water loss evaporation excretion in
urine excretion in feces Water
replacement food and water retention of
metabolic water (by product of chemical
reactions) some insects can absorb water vapor
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Conversion of urea into uric acid A toxic waste
product is converted to a nontoxic substance Can
be excreted as semisolid product with little
water loss terrestrial insects reptiles bird
s amniotic eggs of same Salt gland- marine
birds and turtle- for excretion of salt
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Excretory structures of invertebrates Contractile
vacuole freshwater protozoa, sponges main
function is removal of excess water Some
products are regulated by diffusion Contractile
vacuoles are uncommon in marine protozoans- they
are isoosmotic with sea water and dont need the
vacuoles
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protonephridium
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Protonephridium Fluid enters system through
flame cells Excreted through pores on the
surface No centralized excretory system
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True nephridium is open tubule open at both
ends exchange between tubule and bloodstream
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Vertebrate kidney regulates volume and
composition of fluid
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• Glomerular filtration- protein-free filtrate
• is passed into glomerulus from blood

2. Filtrate is modified as it passes though
tubule system fluid, nutrients and ions are
reabsorbed passively, active transport, ion
pumps 3. Distal tubule- further adjustment of
filtrate concentration under endocrine
control 4. Water excretion- loop of Henle
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Temperature regulation in animals Ectotherms-
body temperature is determined by environment
(e.g., warm up by basking in the
sun) Endotherms- animals generate and retain
enough heat to maintain stable body
temperature (birds and mammals)
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• General types of adaptations
• Rate of heat exchange between animal and
• environment
• body insulation (hair, feathers, fat)
• vasodilation, vasoconstriction
• endotherms- countercurrent heat exchange

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Veins absorb heat from arteries
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2. Cooling by evaporative heat loss if humidity
is low enough respiratory system
(panting) skin (sweating) 3. Behavior _seeking
warmth or cold as needed 4. Changing rate of
metabolic heat production (endotherms, esp.
mammals, birds)
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Most animals are ectotherms. Some are capable of
both, at intervals Invertebrates behavioral and
physiological adjustments Bees and large moths
can be endothermic flight muscles generate
heat honeybees can huddle
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Amphibians and reptiles- usually ectotherms Low
metabolic rates contribute little to
body temperature mostly behavioal
mechanisms amphibians can control mucus
secretion some marine reptiles have
vasoconstriction pythons can warm up by
shivering while incubating eggs
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Fishes body temperature is usually similar to
that of water Some larger fishes are
endothermic swimming muscles generate a lot of
heat circulatory system can help sustain it.
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Mammals and birds maintain high body
temperature balance metabolic heat production
and loss Muscle contraction Hormonal control of
metabolic rate (many mammals and some
birds) brown fat- heat production Vasodilation,
constriction Insulation Evaporative
cooling Feedback mechanisms (hypothalamus, skin)
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Acclimitization Cellular enzyme
levels enzymes with different temperature
optima membrane fluidity heat-shock proteins
(rapid adjustment) generally help cells survive
stress Behavioral torpor ( slowdown) hibernatio
n (winter)
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Small animals may have daily torpor Bats and
shrews feed at night, torpor during day Birds
feed in day, torpor at night Helps them conserve
energy Animals can be much more accommodating
to temperature fluctuations than water
and waste imbalances