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Chapter 25
Control of Body Temperature
and Water Balance
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
Introduction
 Homeostasis is the maintenance of steady internal
conditions despite fluctuations in the external
environment.
 Examples of homeostasis include
– thermoregulation—the maintenance of internal
temperature within narrow limits,
– osmoregulation—the control of the gain and loss of
water and solutes, and
– excretion—the disposal of nitrogen-containing wastes.
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Figure 25.0_1
Chapter 25: Big Ideas
Thermoregulation
Osmoregulation and
Excretion
Figure 25.0_2
THERMOREGULATION
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25.1 An animal’s regulation of body
temperature helps maintain homeostasis
 Thermoregulation is
– the process by which animals maintain an internal
temperature within a tolerable range and
– a form of homeostasis.
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25.1 An animal’s regulation of body
temperature helps maintain homeostasis
 Ectothermic animals
– gain most of their heat from external sources and
– include many fish, most amphibians, lizards, and most
invertebrates.
 Endothermic animals
– derive body heat mainly from their metabolism and
– include birds, mammals, a few reptiles and fish, and
many insects.
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25.2 Heat is gained or lost in four ways
 Heat exchange with the environment may occur by
– conduction—the transfer of heat by direct contact,
– convection—the transfer of heat by movement of air or
liquid past a surface,
– radiation—the emission of electromagnetic waves, or
– evaporation—the loss of heat from the surface of a
liquid that is losing some of its molecules as a gas.
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Figure 25.2
Evaporation
Radiation
Convection
Conduction
25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Five general categories of adaptations help
animals thermoregulate.
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25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Increased metabolic heat production occurs when
– hormonal changes boost the metabolic rate in birds and
mammals,
– birds and mammals shiver,
– organisms increase their physical activity, and
– honeybees cluster and shiver.
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Figure 25.3_UN01
25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Insulation is provided by
– hair,
– feathers, and
– fat layers.
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25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Circulatory adaptations include
– increased or decreased blood flow to skin and
– countercurrent heat exchange, with warm and cold
blood flowing in opposite directions.
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Figure 25.3_1
Figure 25.3_2
Blood from
body core
in artery
Blood
returning to
body core
in vein
35
33C
30
27
20
18
10
9
Blood from
body core
in artery
Blood
returning
to body
core in vein
25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Evaporative cooling may involve
– sweating,
– panting, or
– spreading saliva on body surfaces.
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25.3 Thermoregulation involves adaptations that
balance heat gain and loss
 Behavioral responses
– are used by endotherms and ectotherms and
– include
– moving to the sun or shade,
– migrating, and
– bathing.
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OSMOREGULATION
AND EXCRETION
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25.4 Animals balance the level of water and
solutes through osmoregulation
 Osmoregulation is the homeostatic control of the
uptake and loss of water and solutes such as salt
and other ions.
 Osmosis is one process whereby animals regulate
their uptake and loss of fluids.
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25.4 Animals balance the level of water and
solutes through osmoregulation
 Osmoconformers
– have body fluids with a solute concentration equal to
that of seawater,
– face no substantial challenges in water balance, and
– include many marine invertebrates.
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25.4 Animals balance the level of water and
solutes through osmoregulation
 Osmoregulators
– have body fluids whose solute concentrations differ from
that of their environment,
– must actively regulate water movement, and
– include
– many land animals,
– freshwater animals such as trout, and
– marine vertebrates such as sharks.
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25.4 Animals balance the level of water and
solutes through osmoregulation
 Freshwater fish
– gain water by osmosis (mainly through gills),
– lose salt by diffusion to the more dilute environment,
– take in salt through their gills and in food, and
– excrete excess water in dilute urine.
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Figure 25.4_1
Uptake of
some ions
in food
Osmotic water gain through gills
and other parts of body surface
Uptake
of salt ions
by gills
Fresh water
Excretion of large
amounts of water
in dilute urine
from kidneys
25.4 Animals balance the level of water and
solutes through osmoregulation
 Saltwater fish
– lose water by osmosis from the gills and body surface,
– drink seawater, and
– use their gills and kidneys to excrete excess salt.
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Figure 25.4_2
Gain of water and
salt ions from food
and by intake of
seawater
Osmotic water loss through gills
and other parts of body surface
Excretion of
salt from gills
Salt water
Excretion of excess ions
and small amounts of
water in concentrated
urine from kidneys
25.4 Animals balance the level of water and
solutes through osmoregulation
 Land animals
– face the risk of dehydration,
– lose water by evaporation and waste disposal,
– gain water by drinking and eating, and
– conserve water by
– reproductive adaptations,
– behavior adaptations,
– waterproof skin, and
– efficient kidneys.
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25.5 EVOLUTION CONNECTION: A variety of
ways to dispose of nitrogenous wastes has
evolved in animals
 Metabolism produces toxic by-products.
 Nitrogenous wastes are toxic breakdown products
of proteins and nucleic acids.
 Animals dispose of nitrogenous wastes in different
ways.
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25.5 EVOLUTION CONNECTION: A variety of
ways to dispose of nitrogenous wastes has
evolved in animals
 Ammonia (NH3) is
– poisonous,
– too toxic to be stored in the body,
– soluble in water, and
– easily disposed of by aquatic animals.
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25.5 EVOLUTION CONNECTION: A variety of
ways to dispose of nitrogenous wastes has
evolved in animals
 Urea is
– produced in the vertebrate liver by combining ammonia
and carbon dioxide,
– less toxic,
– easier to store, and
– highly soluble in water.
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25.5 EVOLUTION CONNECTION: A variety of
ways to dispose of nitrogenous wastes has
evolved in animals
 Uric acid is
– excreted by some land animals (insects, land snails,
and many reptiles),
– relatively nontoxic,
– largely insoluble in water,
– excreted as a semisolid paste, conserving water, but
– more energy expensive to produce.
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Figure 25.5
Proteins
Amino acids
Nitrogenous bases
Nucleic acids
NH2
(amino groups)
Most aquatic animals,
including most bony
fishes
Mammals, most
amphibians, sharks,
some bony fishes
Birds and many other
reptiles, insects, land
snails
Uric acid
Ammonia
Urea
25.6 The urinary system plays several major
roles in homeostasis
 The urinary system
– forms and excretes urine and
– regulates water and solutes in body fluids.
 In humans, the kidneys are the main processing
centers of the urinary system.
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25.6 The urinary system plays several major
roles in homeostasis
 Nephrons
– are the functional units of the kidneys,
– extract a fluid filtrate from the blood, and
– refine the filtrate to produce urine.
 Urine is
– drained from the kidneys by ureters,
– stored in the urinary bladder, and
– expelled through the urethra.
Animation: Nephron Introduction
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Figure 25.6
Renal cortex
Renal medulla
Aorta
Inferior
vena cava
Renal artery (red)
and vein (blue)
Ureter
Kidney
Renal pelvis
Urinary bladder
Urethra
The urinary system
Bowman’s
capsule
Glomerulus
Arteriole
from renal
artery
1
Ureter
Proximal tubule
Capillaries
3
Arteriole
from
glomerulus
Distal
tubule
Collecting
duct
From
another
nephron
Branch of
renal vein
The kidney
Bowman’s
capsule
Tubule
Renal cortex
Branch of
renal artery
Branch of
renal vein
Collecting
duct
Renal medulla
2
Loop of Henle
with capillary
network
Detailed structure of a nephron
To
renal
pelvis
Orientation of a nephron within the kidney
Figure 25.6_1
Aorta
Inferior
vena cava
Renal artery (red)
and vein (blue)
Ureter
Urinary bladder
Urethra
The urinary system
Kidney
Figure 25.6_2
Renal cortex
Renal medulla
Renal pelvis
Ureter
The kidney
Figure 25.6_3
Bowman’s
capsule
Tubule
Renal cortex
Branch of
renal artery
Branch of
renal vein
Collecting
duct
Renal medulla
To
renal
pelvis
Orientation of a nephron within the kidney
Figure 25.6_4
Bowman’s
capsule
Glomerulus
Arteriole
from renal
artery
1
Proximal tubule
Capillaries
3
Arteriole
from
glomerulus
From
another
nephron
Branch of
renal vein
2
Distal
tubule
Collecting
Duct
Loop of Henle
with capillary
network
Detailed structure of a nephron
25.7 Overview: The key processes of the urinary
system are filtration, reabsorption,
secretion, and excretion
 Filtration
– Blood pressure forces water and many small molecules
through a capillary wall into the start of the kidney
tubule.
 Reabsorption
– refines the filtrate,
– reclaims valuable solutes (such as glucose, salt, and
amino acids) from the filtrate, and
– returns these to the blood.
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Figure 25.7
Bowman’s
From
capsule
renal
artery
Filtration
Reabsorption
Secretion
Excretion
Nephron tubule
H2O, other small molecules
Urine
Interstitial fluid
Capillary
To renal vein
Figure 25.7_1
From Bowman’s
Filtration
renal capsule
artery
Nephron tubule
H2O, other small molecules
Interstitial fluid
Capillary
Figure 25.7_2
Reabsorption
Secretion
Excretion
Nephron tubule
Urine
Capillary
To renal vein
25.7 Overview: The key processes of the urinary
system are filtration, reabsorption,
secretion, and excretion
 Substances in the blood are transported into the
filtrate by the process of secretion.
 By excretion the final product, urine, is excreted
via the ureters, urinary bladder, and urethra.
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Figure 25.7
Bowman’s
From
capsule
renal
artery
Filtration
Reabsorption
Secretion
Excretion
Nephron tubule
H2O, other small molecules
Urine
Interstitial fluid
Capillary
To renal vein
25.8 Blood filtrate is refined to urine through
reabsorption and secretion
 Reabsorption in the proximal and distal tubules
removes
– nutrients,
– salt, and
– water.
 pH is regulated by
– reabsorption of HCO3– and
– secretion of H+.
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25.8 Blood filtrate is refined to urine through
reabsorption and secretion
 High NaCl concentration in the medulla promotes
reabsorption of water.
Animation: Bowman’s Capsule and Proximal Tubule
Animation: Collecting Duct
Animation: Effect of ADH
Animation: Loop of Henle and Distal Tubule
© 2012 Pearson Education, Inc.
Figure 25.8
Bowman’s
capsule
Proximal tubule
Nutrients H2O

NaCl HCO3
1
Distal tubule
H2O
NaCl
HCO3
Blood
Cortex
Filtrate composition
H2O
Salts (NaCl and others)
HCO3
H
Urea
Glucose
Amino acids
Some drugs
K
Some H
drugs
and poisons
H
3
Collecting
duct
Medulla
Interstitial
Loop of
fluid
Henle
2
NaCl
NaCl
H2O
NaCl
Urea
H2O
Reabsorption
Secretion
Filtrate movement
Urine (to
renal pelvis)
Figure 25.8_1
Bowman’s
capsule
Proximal tubule
Nutrients H2O

NaCl HCO3
Blood
Cortex
Filtrate composition
H2O
Salts (NaCl
and others)
HCO3
H
Urea
Glucose
Amino acids
Some drugs
Some H
drugs
and poisons
Medulla
Reabsorption
Secretion
Filtrate movement
Figure 25.8_2
Proximal tubule
Nutrients H2O

NaCl HCO3
Cortex
1
Some H
drugs
and poisons
Distal tubule
H2O
NaCl HCO3
K H
3
Collecting
duct
Medulla
Interstitial
Loop of
fluid
Henle
2
NaCl
NaCl
H2O
NaCl
Urea
H2O
Reabsorption
Secretion
Filtrate
movement
Urine (to
renal pelvis)
25.9 Hormones regulate the urinary system
 Antidiuretic hormone (ADH) regulates the
amount of water excreted by the kidneys by
– signaling nephrons to reabsorb water from the filtrate,
returning it to the blood, and
– decreasing the amount of water excreted.
 Diuretics
– inhibit the release of ADH and
– include alcohol and caffeine.
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25.10 CONNECTION: Kidney dialysis can be
lifesaving
 Kidney failure can result from
– hypertension,
– diabetes, and
– prolonged use of common drugs, including alcohol.
 A dialysis machine
– removes wastes from the blood and
– maintains its solute concentration.
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Figure 25.9
Line from artery to apparatus
Pump
Line from
apparatus
to vein
Tubing made of a
selectively permeable
membrane
Dialyzing
solution
Fresh dialyzing
solution
Used dialyzing solution
(with urea and excess ions)
Figure 25.9_1
Line from artery to apparatus
Pump
Line from
apparatus
to vein
Tubing made of a
selectively permeable
membrane
Dialyzing
solution
Fresh dialyzing
solution
Used dialyzing solution
(with urea and excess ions)
Figure 25.9_2
You should now be able to
1. Explain how bear physiology adjusts during
dormancy.
2. Describe four ways that heat is gained or lost by
an animal.
3. Describe five categories of adaptations that help
animals thermoregulate.
4. Compare the osmoregulatory problems of
freshwater fish, saltwater fish, and terrestrial
animals.
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You should now be able to
5. Compare the three ways that animals eliminate
nitrogenous wastes.
6. Describe the structure and functions of the human
kidney.
7. Explain how the kidney promotes homeostasis.
8. Describe four major processes that produce urine.
9. Describe the key events in the conversion of
filtrate into urine.
10. Explain why a dialysis machine is necessary and
how it works.
© 2012 Pearson Education, Inc.
Figure 25.UN02
Gain Water
Lose Water
Salt
Osmosis
Excretion
Pump in
Saltwater Fish
Drinking
Osmosis
Excrete,
pump out
Land Animal
Drinking,
eating
Evaporation,
urinary system
Freshwater
Fish
Figure 25.UN05
Homeostasis
involves processes of
(b)
(a)
maintains
animal may balance of
be
(c)
both done by
water and
solutes
human
kidney
requirements
depend on
(d)
involves
removal of
nitrogenous
wastes
form may be
(e)
mechanisms
mostly
endotherm
mechanisms
include
(f)
(g)
depends on
(h)
(i)
may be
heat
production, insulation,
countercurrent
heat exchange
ocean, fresh
water,
land
reproduction
(where embryo
develops)
Figure 25.UN06
(a)
(b)
(c)
Bowman’s
capsule
From renal
artery
To renal
vein
Glomerulus
Tubule
Loop
of Henle Capillaries
Collecting
duct
(d)