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Body Temperature
Enzymes: Rxn rates inc. 2-3 times with each 10 0 C temp. inc.
(until denatured)

Each species has an optimal temp. range for metabolic rxns to be efficient

Thermoregulation  Organisms maintain their body temp within optimal range (various methods)

Heat Gain/Loss

Heat Gain/Loss (HIGH to LOW)
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Conduction = molecule to molecule
(ie: hot concrete and feet in summer)
Convection = heat transfer b/t object and H
2
O or air moving across it
Radiation = electromagnetic waves transferred as heat (ie: suns rays)
Evaporative Cooling = lowers temp by releasing H sweating)
2
O as vapor (ie:

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Ectotherms and Endotherms
Ectotherms (“cold-blooded”) maintain a temperature close to external temp.
•Low metabolic requirements (little heat generated)
•Most fish, reptiles, amphibians
Endotherms (“warm-blooded”) maintain a constant temp. that may vary significantly from external temp
(species dependent)
•High metabolic rate (lots of heat!)
•Humans, other mammals, and birds

Endotherms/Ectotherms

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Endothermic Advantages
Higher temp allows for inc. metabolic rate
More energy is generated
Can perform more vigorous activities for more sustained periods
Allows terrestrial life (more temp. fluctuations than H
2
O)
Disadvantage : Require more frequent meals for higher aerobic resp. rate

Vasodilation and Vasoconstriction
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
Vasodilation  Blood vessels dilate (expand) in order to release more heat
Vasoconstriction  Blood vessels constrict in order to limit heat loss in the cold

Behavioral Controls

Basking in the sun to raise body temp

Hibernation

Migration to different climates
(birds)

Inc or dec metabolic rate in hot/cold temps

Certain insects huddle to generate more heat

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Insulation

Thermoregulation in Humans


Thermoregulation in Humans
Heat receptors in skin

Receptors send hot/cold signal to hypothalamus (brain)

Hypothalamus regulates vasodilation and vasoconstriction

Extreme Hot/Cold Environments

Cryoprotectants  Certain organisms (some frog eggs, arctic fish) have a biologically produced antifreeze

Heat shock proteins  Produced in response to heat. Bind to enzymes and other proteins to inhibit denaturization

Hibernation

Bears, squirrels go into a deep sleep during winter in order to avoid harsh conditions

Very low energy demands

Very low metabolic rate

Hibernation

Osmoregulation (Water Balance)

Organisms must balance their water and solute concentrations

Water uptake and loss must remain essentially equal

Cells could swell or shrivel

Water flows from high water potential (low [solute]) to low water potential (high [solute])



Osmoregulators/Osmoconformors
Osmoregulators maintain a constant solute concentration different from that of ext. environment
•Freshwater, terrestrial, some marine
•Costs energy (active transport)
Osmoconformers maintain solute concentration equal to that of surroundings
•Many marine invertebrates

Osmoregulation

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
Waste Disposal
Elimination of toxic materials is needed to maintain homeostasis
Nitrogenous wastes are very toxic to living cells
•Urea  Many terrestrial organisms, lowest toxicity, high energy requirement (humans)
•Uric Acid  Birds, insects reptiles, least water lost
•Ammonia  Fish, aquatic organisms, most toxic

Nitrogenous Waste

Selective Reabsorption and Secretion



Organisms will filter their wastes and reabsorb anything that may be of use
Accomplished in tubules (present in human kidneys)
May also secrete more waste materials into urine

Malpighian Tubules
Remove nitrogenous wastes from open circulatory system of insects

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Vertebrate Urinary System
Kidneys
•Function in osmoregulation and reabsorption
•Contain a network of tubules
Renal Artery  Blood to kidney
Renal Vein  Blood from kidney
Ureter  Carries urine to bladder
Bladder  Stores urine
Urethra  Tube that exits the body

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Vertebrate Kidneys
Two regions
•Renal cortex and renal medulla
Contains millions of nephrons
•Microscopic tubules
Glomerulus  Network of capillaries serving each nephron with a blood supply
Bowman’s Capsule  End of tubule that surrounds the glomerulus

Human Kidney

Kidneys



 nephron and collecting duct are lined by a transport epithelium process filtrate to form urine reabsorb solutes and water
•sugar, vitamins, and other organic nutrients from the initial filtrate and about 99% of the water reduce 180 L of initial filtrate to about 1.5 L of urine to be voided

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Kidney Function
Proximal Tubule  NaCl and H
2
O reabsorption and pH regulation
Descending Loop of Henle  H
2
O reabsorption
Ascending Loop of Henle  NaCl reabsorption
Distal Tubule  K + and NaCl balance, pH regulation, some H
2
O reabsorbed
Collecting Duct  NaCl reabsorption,
H
2
O reabsorption
As it moves through the kidney, urine becomes more concentrated with unusable waste

Kidneys

Kidneys give terrestrial vertebrates the ability to regulate their osmotic balance

Without kidneys, life on land would not be possible