Download Chapter 25: Internal Environment

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 25
Control of the Internal
Environment
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Let Sleeping Bears Lie
• Bears don’t technically hibernate
– They do enter a dormant state, when their body
temperature drops by several degrees
• Bears are endotherms
– Endothermic animals derive
most of their body heat from
metabolism
– Ectothermic animals warm
themselves mainly by absorbing
heat from their surroundings
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• Dormant bears have internal homeostatic
mechanisms that compensate for fluctuations
in the external environment
– Thermoregulation maintains
the body temperature within
a tolerable range
– Osmoregulation controls the
gain and loss of water and
dissolved solutes
– Excretion is the disposal of
metabolic wastes
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THERMOREGULATION
25.1 Heat is gained or lost in four ways
• Body temperature regulation requires
adjustment to heat gained from or lost to an
animal’s environment
Convection
Radiation
Evaporation
Conduction
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Figure 25.1
25.2 Thermoregulation depends on both heat
production and heat gain or lost
• Both endotherms and ectotherms may change
their rate of heat loss
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• Hormonal changes may increase heat
production by raising the metabolic rate
– Fur and feathers help the body retain heat
– Shivering, as these honeybees are doing, also
increases metabolic heat production
Figure 25.2A
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• Blood flow to the skin affects heat loss
Top view of shark
Skin
Blood vessels
of gills
Artery
Vein
Capillary network
within muscle
Heart
Artery and vein
under the skin
Dorsal aorta
Figure 25.2B
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Body surface (cool)
• In a countercurrent heat
exchanger, blood from the
core body warms cooler
blood returning from the
gills or limbs
– This process
conserves body heat
18˚
C
20˚
C
20˚
22˚
22˚
24˚
24˚
26˚
Blood
flow
Heat
transfer
Inner body (warm)
Figure 25.2C
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25.3 Behavior often affects body temperature
• Basking in the
sun
• Sitting in the
shade
• Bathing
• Burrowing or
huddling
• Migrating
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Figure 25.3
25.4 Reducing the metabolic rate saves energy
• Torpor is a state of reduced activity and
lowered metabolic rate
– Hibernation
in cold
weather
– Estivation
in warm
weather
Figure 25.4
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OSMOREGULATION AND EXCRETION
25.5 Osmoregulation: All animals balance the gain
and loss of water and dissolved solutes
• Many marine animals are osmoconformers
– Their body fluids have the same concentration
of solutes as sea water
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• Osmoregulators control water and solute
concentrations
– Freshwater fishes gain water by osmosis and
tend to lose solutes
Osmotic water gain through gills
and other parts of body surface
Uptake of water
and some ions
in food
Uptake of
salt ions
by gills
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Excretion of
large amounts of
water in dilute
urine from kidneys
Figure 25.5A
• Many marine fishes lose water by osmosis,
drink seawater, and excrete excess salts
Gain of water and salt
ions from food
and by drinking
seawater
Excretion of salt
ions from gills
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Osmotic water loss
through gills and other
parts of body surface
Excretion of salt ions
and small amounts
of water in scanty
urine from kidneys
Figure 25.5B
• Land animals gain water by drinking and
eating
– They lose water and solutes by evaporation and
waste disposal
– Their kidneys, behavior, and waterproof skin
conserve water
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25.6 Connection: Sweating can produce serious
water loss
• Water lost in thermoregulation can cause
osmoregulatory problems
– Drinking water
is the best way
to prevent
dehydration
during exercise
Figure 25.6
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25.7 Some animals face seasonal dehydration
• Many small invertebrates can dehydrate and
become dormant when their environment
dries up
Figure 25.7
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25.8 Animals must dispose of nitrogenous wastes
• Nitrogen-containing wastes are toxic byproducts of protein and nucleic acid
breakdown
– Ammonia is poisonous but soluble and easily
disposed of
– Urea is less toxic and easy to store and excrete
– Some land animals save water by excreting a
virtually dry waste
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Proteins
Nucleic acids
Amino acids
Nitrogenous bases
–NH2
Amino groups
Most aquatic animals,
including many fishes
Mammals, amphibians,
sharks, some bony fishes
Ammonia
Birds, insects, many
reptiles, land snails
Urea
Uric acid
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Figure 25.8
25.9 The excretory system plays several major
roles in homeostasis
• The excretory
system
– expels wastes
– regulates
water and
salt balance
(Inferior
vena cava)
Renal artery
and vein
Kidney
(Aorta)
Ureter
Bladder
Urethra
A. THE EXCRETORY SYSTEM
Figure 25.9A
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• The two human kidneys each contain about a
million functional units called nephrons
• Urine leaves the kidneys via the ureters
– It is stored in the urinary bladder
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Renal
medulla
Renal
cortex
Renal
pelvis
Bowman’s
capsule
Nephron
tubule
Renal
cortex
Renal artery
Renal vein
Collecting
duct
Renal
medulla
Ureter
To
renal
pelvis
B. THE KIDNEY
C. ORIENTATION OF A NEPHRON WITHIN THE KIDNEY
Figure 25.9B, C
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• Each nephron
consists of a
folded tubule
and associated
blood vessels
Bowman’s capsule
Arteriole
from renal
artery
Capillaries
Arteriole
from glomerulus
– The nephrons
extract a filtrate
from the blood
– They refine the
filtrate into a
much smaller
amount of urine
1 Proximal tubule
Glomerulus
Branch of
renal vein
3 Distal
tubule
From
another
nephron
Collecting
duct
2 Loop of Henle
with capillary
network
D. DETAILED STRUCTURE OF A NEPHRON
Figure 25.9D
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25.10 Overview: The key functions of the excretory
system are filtration, reabsorption, secretion,
and excretion
• Filtration
– Blood pressure forces water and many solutes
from the blood into the nephron
• Reabsorption
– The nephron tubule reclaims valuable solutes
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• Secretion
– The nephron removes substances and adds them
to the filtrate
• The product of all of the above processes is
urine, which is excreted
FILTRATION
Nephron tubule
REABSORPTION
H2O, other small molecules
SECRETION
EXCRETION
Urine
Capillary
Figure 25.10
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25.11 From blood to filtrate to urine: A closer look
• The proximal tubule reabsorbs
– nutrients
– salts
– water
• Antidiuretic hormone and other hormones
regulate the amount of salt and water the
kidneys excrete
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• Controlled secretion of H+ and reabsorption of
bicarbonate ions help regulate blood pH
• Secretion also includes the active transport of
drugs and poisons
• Reabsorption of salts and urea promote the
osmotic reabsorption of water
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Bowman’s
capsule
Proximal tubule
NaCl
H2O
HCO3–
Glucose and
amino acids
Distal tubule
NaCl
H2O
HCO3–
Blood
Filtrate
H2O
Salts (NaCl, etc.)
HCO3–
H+
Urea
Glucose
Some NH H+
3
drugs
and poisons
K+
H+
Collecting
duct
CORTEX
MEDULLA
Amino acids
Some drugs
Loop of
Henle
NaCl
NaCl
H2O
Reabsorption
Active transport
Passive transport
NaCl
Urea
H2O
Secretion
(active transport)
Urine (to renal pelvis)
Figure 25.11
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25.12 Connection: Kidney dialysis can be a
lifesaver
• A dialysis machine compensates for kidney
failure
– It performs the function of the nephrons by
removing wastes from the blood and
maintaining its solute concentration
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Line from artery
to apparatus
Pump
Line from
apparatus
to vein
Tubing made of a
selectively permeable
membrane
Dialyzing
solution
Fresh dialyzing
solution
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Used dialyzing
solution
(with urea and
excess salts)
Figure 25.12
HOMEOSTATIC FUNCTIONS OF THE LIVER
25.13 The liver is vital in homeostasis
• It assists the kidneys by
– making urea from ammonia
– breaking down toxic chemicals
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• Blood from the
intestines flows
through the liver
before
distribution to
the rest of the
body
Inferior
vena cava
Hepatic vein
Liver
– This allows the
liver to adjust
the blood’s
chemical
content
Hepatic
portal vessel
Intestines
Figure 25.13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings