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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mark Louie D. Lopez
Department of Biology
College of Science
Polytechnic University of the Philippines
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OUTLINE
• Overview: Diverse Forms, Common
Challenges
• Animals inhabit almost every part of the
biosphere
• All animals face a similar set of problems,
including how to nourish themselves
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FORM AND FUNCTION RELATION
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SELECTION OF FORMS FIT TO FUNCTION
FORM : FUNCTIONN
atu
ral S
ele
ctio
n
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PHYSICAL LAWS IN FORM AND FUNCTION
Physical laws and the need to
exchange materials with the
environment place certain limits on
the range of animal forms
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EVOLUTIONARY CONVERGENCE
Reflects different species’
independent adaptation to
a similar environmental
challenge
(a) Tuna
(b) Shark
(c) Penguin
(d) Dolphin
(e) Seal
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EXCHANGE WITH THE ENVIRONMENT
• Animal’s size and shape have a direct effect
on how the animal exchanges energy and
materials with its surroundings
• Exchange with the environment occurs as
substances dissolved in the aqueous
medium diffuse and are transported across the
cells’ plasma membranes
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• A single-celled protist living in water has a
sufficient surface area of plasma membrane
to service its entire volume of cytoplasm
EXCHANGE OF MATERIAL IN PROKARYOTE
Diffusion
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EXCHANGE OF MATERIAL IN EUKARYOTE
• Multicellular organisms with a sac body plan have
body walls that are only two cells thick, facilitating
diffusion of materials
Mouth
Gastrovascular
cavity
Diffusion
Diffusion
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• Organisms with more complex body plans have
highly folded internal surfaces specialized for
exchanging materials
EXCHANGE OF MATERIAL IN COMPLEX FORM
Respiratory
system
Circulatory
system
Excretory
system
Digestive
system
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LEVELS OF ORGANIZATIONAL STRUCTURE
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• Different types of tissues
– Have different structures that are suited to their
functions
• Tissues are classified into four main
categories
– Epithelial, connective, muscle, and nervous
TISSUE STRUCTURE AND FUNCTION
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EPITHELIAL TISSUE
• Epithelial tissue
– Covers the outside of the body and lines
organs and cavities within the body
– Contains cells that are closely joined
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EPITHELIAL TISSUE
EPITHELIAL TISSUE
Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often
located where secretion or active absorption of substances is an important function.
A stratified columnar
epithelium
A simple
columnar
epithelium
A pseudostratified
ciliated columnar
epithelium
Stratified squamous epithelia
Simple squamous epithelia
Cuboidal epithelia
Basement membrane
40 µm
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CONNECTIVE TISSUE
• Connective tissue
– Functions mainly to bind and support other
tissues
– Contains sparsely packed cells scattered
throughout an extracellular matrix
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CONNECTIVE TISSUE
Collagenous
fiber
Elastic
fiber
Chondrocytes
Chondroitin
sulfate
Loose connective tissue
Fibrous connective tissue
100 µ
m
100 µm
Nuclei
30 µm
Bone Blood
Central
canal
Osteon
700 µm 55 µm
Red blood cells
White blood cell
Plasma
Cartilage
Adipose tissue
Fat droplets
150 µ
m
CONNECTIVE TISSUE
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MUSCLE TISSUE
• Muscle tissue
– Is composed of long cells called muscle fibers
capable of contracting in response to nerve
signals
– Is divided in the vertebrate body into three
types: skeletal, cardiac, and smooth
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NERVOUS TISSUE
• Nervous tissue
– Senses stimuli and transmits signals
throughout the animal
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MUSCLE AND NERVOUS TISSUE
MUSCLE TISSUESkeletal muscle
100 µm
Multiple
nuclei
Muscle fiber
Sarcomere
Cardiac muscle
Nucleus Intercalated
disk
50 µm
Smooth muscle Nucleus
Muscle
fibers
25 µm
NERVOUS TISSUE
Neurons Process
Cell body
Nucleus
50 µm
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ORGANS AND ORGAN SYSTEMS
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Lumen of
stomach
Mucosa. The mucosa is an
epithelial layer that lines
the lumen.
Submucosa. The submucosa is
a matrix of connective tissue
that contains blood vessels
and nerves.
Muscularis. The muscularis consists
mainly of smooth muscle tissue.
0.2 mm
Serosa. External to the muscularis is the serosa,
a thin layer of connective and epithelial tissue.
TISSUES ORGANIZED TO FORM ORGANS
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ORGAN SYSTEMS
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• Animals use the chemical energy in food to
sustain form and function
• All organisms require chemical energy for
growth, repair, physiological processes,
regulation, and reproduction
ENERGY FOR FORM AND FUNCTION
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• The flow of energy through an animal, its
bioenergetics
– Ultimately limits the animal’s behavior, growth,
and reproduction
– Determines how much food it needs
BIOENERGETICS
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ENERGY SOURCES AND ALLOCATION
• Animals harvest chemical energy
– From the food they eat
• Once food has been digested, the energy-
containing molecules
– Are usually used to make ATP, which powers
cellular work
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• After the energetic needs of staying alive are
met, any remaining molecules from food can be
used in biosynthesis
ENERGY FOR BIOMOLECULE PRODUCTION
Organic molecules
in food
Digestion and
absorption
Nutrient molecules
in body cells
Cellular
respiration
Biosynthesis:
growth,
storage, and
reproductionCellular
work
Heat
Energy
lost in
feces
Energy
lost in
urine
Heat
Heat
External
environment
Animal
body
Heat
Carbon
skeletons
ATP
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• An animal’s metabolic rate
– Is the amount of energy an animal uses in a
unit of time
– Can be measured in a variety of ways
QUANTIFYING ENERGY USE
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METABOLIC RATE
• One way to measure metabolic rate is to
determine the amount of oxygen consumed or
carbon dioxide produced by an organism
This photograph shows a ghost crab in a
respirometer. Temperature is held constant in the
chamber, with air of known O2 concentration flow-
ing through. The crab’s metabolic rate is calculated
from the difference between the amount of O2
entering and the amount of O2 leaving the
respirometer. This crab is on a treadmill, running
at a constant speed as measurements are made.
(a)
(b) Similarly, the metabolic rate of a man
fitted with a breathing apparatus is
being monitored while he works out
on a stationary bike.
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• An animal’s metabolic rate is closely related
to its bioenergetic strategy
BIOENERGETIC STRATEGIES
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• Birds and mammals are mainly endothermic,
meaning that
– Their bodies are warmed mostly by heat
generated by metabolism
– They typically have higher metabolic rates
ENDOTHERMIC ORGANISMS
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ECTOTHERMIC ORGANISMS
• Amphibians and reptiles other than birds are
ectothermic, meaning that
– They gain their heat mostly from external
sources
– They have lower metabolic rates
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SIZE AND METABOLIC RATE
• Metabolic rate per gram is inversely related to
body size among similar animals
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• The basal metabolic rate (BMR)
– Is the metabolic rate of an endotherm at rest
• The standard metabolic rate (SMR)
– Is the metabolic rate of an ectotherm at rest
• For both endotherms and ectotherms
– Activity has a large effect on metabolic rate
ACTIVITY AND METABOLIC RATE
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• In general, an animal’s maximum possible
metabolic rate is inversely related to the
duration of the activity
Maxim
um
meta
bolic
rate
(kcal/m
in; lo
g s
cale
)
500
100
50
10
5
1
0.5
0.1
A H
AH
A
AA
HH
H
A = 60-kg alligator
H = 60-kg human
1
second
1
minute1
hourTime interval
1
day
1
week
Key
Existing intracellular ATP
ATP from glycolysis
ATP from aerobic respiration
METABOLIC RATE AND ACTIVITY DURATION
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• Different species of animals
– Use the energy and materials in food in
different ways, depending on their
environment
ENERGY BUDGETS
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• An animal’s use of energy is partitioned to
BMR (or SMR), activity, homeostasis,
growth, and reproduction
ENERGY UTILIZATION
Endotherms Ectotherm
Annual energ
y e
xpenditure
(kcal/yr)
800,000 Basal
metabolic
rate
ReproductionTemperature
regulation costs
Growth
Activity
costs
60-kg female human
from temperate climate
Total annual energy expenditures(a)
340,000
4-kg male Adélie penguin
from Antarctica (brooding)
4,000
0.025-kg female deer mouse
from temperate
North America
8,000
4-kg female python
from Australia
Energ
y e
xpenditure
per
unit m
ass
(kcal/kg•d
ay)
438
Deer mouse
233
Adélie penguin
36.5
Human
5.5
Python
Energy expenditures per unit mass (kcal/kg•day)(b)
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HOMEOSTASIS
• The internal environment of vertebrates
– Is called the interstitial fluid, and is very
different from the external environment
• Homeostasis is a balance between external
changes
– And the animal’s internal control mechanisms
that oppose the changes
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• Regulating and conforming
– Are two extremes in how animals cope with
environmental fluctuations
REGULATING AND CONFORMING
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• An animal is said to be a regulator
– If it uses internal control mechanisms to
moderate internal change in the face of
external, environmental fluctuation
• An animal is said to be a conformer
– If it allows its internal condition to vary with
certain external changes
REGULATING AND CONFORMING
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• Mechanisms of homeostasis
– Moderate changes in the internal environment
MECHANISMS OF HOMEOSTASIS
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MECHANISMS OF HOMEOSTASIS
• A homeostatic control system has three
functional components
Response
No heat
produced
Room
temperature
decreases
Heater
turned
off
Set point
Too
hot
Set
point
Control center:
thermostat
Room
temperature
increases
Heater
turned
on
Too
cold
Response
Heat
produced
Set
point
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NEGATIVE FEEDBACK
• Most homeostatic control systems function by
negative feedback
– Where buildup of the end product of the
system shuts the system off
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POSITIVE FEEDBACK
• A second type of homeostatic control system is
positive feedback
– Which involves a change in some variable that
triggers mechanisms that amplify the change
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THERMOREGULATION
• Thermoregulation contributes to homeostasis
and involves anatomy, physiology, and
behavior
• Thermoregulation
– Is the process by which animals maintain an
internal temperature within a tolerable range
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• Ectotherms
– Include most invertebrates, fishes, amphibians,
and non-bird reptiles
• Endotherms
– Include birds and mammals
ECTOTHERMS AND ENDOTHERMS
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• In general, ectotherms
– Tolerate greater variation in internal temperature
than endotherms
ECTOTHERMS
River otter (endotherm)
Largemouth bass (ectotherm)
Ambient (environmental) temperature (°C)
Bo
dy t
em
pe
ratu
re (
°C)
40
30
20
10
10 20 30 400
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• Endothermy is more energetically expensive
than ectothermy
– But buffers animals’ internal temperatures
against external fluctuations
– And enables the animals to maintain a high
level of aerobic metabolism
ENDOTHERMS
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MODES OF HEAT EXCHANGE
• Organisms exchange heat by four physical processes
Radiation is the emission of electromagnetic
waves by all objects warmer than absolute
zero. Radiation can transfer heat between
objects that are not in direct contact, as when
a lizard absorbs heat radiating from the sun.
Evaporation is the removal of heat from the surface of a
liquid that is losing some of its molecules as gas.
Evaporation of water from a lizard’s moist surfaces that
are exposed to the environment has a strong cooling effect.
Convection is the transfer of heat by the
movement of air or liquid past a surface,
as when a breeze contributes to heat loss
from a lizard’s dry skin, or blood moves
heat from the body core to the extremities.
Conduction is the direct transfer of thermal motion (heat)
between molecules of objects in direct contact with each
other, as when a lizard sits on a hot rock.
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BALANCING HEAT LOSS AND GAIN
• Thermoregulation involves physiological and
behavioral adjustments
– That balance heat gain and loss
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INSULATION
• Insulation, which is a major thermoregulatory
adaptation in mammals and birds
– Reduces the flow of heat between an animal
and its environment
– May include feathers, fur, or blubber
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INSULATION IN MAMMALS
Hair
Sweatpore
Muscle
Nerve
Sweat
gland
Oil gland
Hair follicle
Blood vessels
Adipose tissue
Hypodermis
Dermis
Epidermis
• In mammals, the integumentary system acts
as insulating material
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• Many endotherms and some ectotherms
– Can alter the amount of blood flowing between
the body core and the skin
CIRCULATORY ADAPTATIONS
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• In vasodilation
– Blood flow in the skin increases, facilitating
heat loss
• In vasoconstriction
– Blood flow in the skin decreases, lowering heat
loss
CIRCULATORY ADAPTATIONS
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• Many marine mammals and birds have arrangements of
blood vessels called countercurrent heat exchangers
that are important for reducing heat loss
CIRCULATORY ADAPTATIONS
In the flippers of a dolphin, each artery is
surrounded by several veins in a
countercurrent arrangement, allowing
efficient heat exchange between arterial
and venous blood.
Canada
goose
Artery Vein
35°C
Blood flow
Vein
Artery
30º
20º
10º
33°
27º
18º
9º
Pacific
bottlenose
dolphin
2
1
3
2
3
Arteries carrying warm blood down the
legs of a goose or the flippers of a dolphin
are in close contact with veins conveying
cool blood in the opposite direction, back
toward the trunk of the body. This
arrangement facilitates heat transfer
from arteries to veins (black
arrows) along the entire length
of the blood vessels.
1
Near the end of the leg or flipper, where
arterial blood has been cooled to far below
the animal’s core temperature, the artery
can still transfer heat to the even colder
blood of an adjacent vein. The venous blood
continues to absorb heat as it passes warmer
and warmer arterial blood traveling in the
opposite direction.
2
As the venous blood approaches the
center of the body, it is almost as warm
as the body core, minimizing the heat lost
as a result of supplying blood to body parts
immersed in cold water.
3
1 3
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COUNTERCURRENT HEAT EXCHANGERS
• Some specialized bony fishes and sharks
– Also possess countercurrent heat exchangers
21º25º 23º
27º
29º31º
Body cavity
Skin
Artery
Vein
Capillary
network within
muscle
Dorsal aorta
Artery and
vein under
the skin
Heart
Blood
vessels
in gills
(a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintains
temperatures in its main swimming muscles that are much higher
than the surrounding water (colors indicate swimming muscles cut
in transverse section). These temperatures were recorded for a tuna
in 19°C water.
(b) Great white shark. Like the bluefin tuna, the great white shark
has a countercurrent heat exchanger in its swimming muscles that
reduces the loss of metabolic heat. All bony fishes and sharks lose
heat to the surrounding water when their blood passes through the
gills. However, endothermic sharks have a small dorsal aorta,
and as a result, relatively little cold blood from the gills goes directly
to the core of the body. Instead, most of the blood leaving the gills
is conveyed via large arteries just under the skin, keeping cool blood
away from the body core. As shown in the enlargement, small
arteries carrying cool blood inward from the large arteries under the
skin are paralleled by small veins carrying warm blood outward from
the inner body. This countercurrent flow retains heat in the muscles.
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COUNTERCURRENT HEAT EXCHANGERS
• Many endothermic insects
– Have countercurrent heat exchangers that help
maintain a high temperature in the thorax
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COOLING BY EVAPORATIVE HEAT LOSS
• Many types of animals
– Lose heat through the evaporation of water in
sweat
– Use panting to cool their bodies
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• Bathing moistens the skin which helps to cool
an animal down
BEHAVIORAL RESPONSES
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• Both endotherms and ectotherms
– Use a variety of behavioral responses to
control body temperature
BEHAVIORAL RESPONSES
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BEHAVIORAL RESPONSES
• Some terrestrial invertebrates have certain
postures that enable them to minimize or
maximize their absorption of heat from the sun
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ADJUSTING METABOLIC HEAT PRODUCTION
• Some animals can regulate body temperature
– By adjusting their rate of metabolic heat
production
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• Many species of flying insects use shivering to
warm up before taking flight
ADJUSTING METABOLIC HEAT PRODUCTION
PREFLIGHT PREFLIGHT
WARMUPFLIGHT
Thorax
Abdomen
Te
mp
era
ture
(°C
)
Time from onset of warmup (min)
40
35
30
25
0 2 4
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• Mammals regulate their body temperature
– By a complex negative feedback system that
involves several organ systems
FEEDBACK MECHANISMS IN THERMOREGULATION
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• In humans, a specific part of
the brain, the hypothalamus
– Contains a group of nerve
cells that function as
a thermostat
FEEDBACK MECHANISMS IN THERMOREGULATION
Thermostat in
hypothalamus
activates cooling
mechanisms.
Sweat glands secrete
sweat that evaporates,
cooling the body.
Blood vessels
in skin dilate:
capillaries fill
with warm blood;
heat radiates from
skin surface. Body temperature
decreases;
thermostat
shuts off cooling
mechanisms.
Increased body
temperature (such
as when exercising
or in hot
surroundings)
Homeostasis:
Internal body temperature
of approximately 36–38C
Body temperature
increases;
thermostat
shuts off warming
mechanisms.
Decreased body
temperature
(such as when
in cold
surroundings)
Blood vessels in skin
constrict, diverting blood
from skin to deeper tissues
and reducing heat loss
from skin surface.
Skeletal muscles rapidly
contract, causing shivering,
which generates heat.
Thermostat in
hypothalamus
activates
warming
mechanisms.
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ADJUSTMENT TO CHANGING TEMPERATURES
• In a process known as acclimatization
– Many animals can adjust to a new range of
environmental temperatures over a period of
days or weeks
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ADJUSTMENT TO CHANGING TEMPERATURES
• Acclimatization may involve cellular
adjustments
– Or in the case of birds and mammals,
adjustments of insulation and metabolic heat
production
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TORPOR AND ENERGY CONSERVATION
• Torpor
– Is an adaptation that enables animals to save
energy while avoiding difficult and dangerous
conditions
– Is a physiological state in which activity is low
and metabolism decreases
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. Lop
ez
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Hibernation is long-term torpor
– That is an adaptation to winter cold and food scarcity during which the animal’s body temperature declines
TORPOR AND ENERGY CONSERVATION
Additional metabolism that would be
necessary to stay active in winter
Actual
metabolism
Body
temperature
Arousals
Outside
temperature Burrow
temperature
June August October December February April
Tem
pera
ture
(°C
)M
eta
bolic
rate
(kcal per
day)
200
100
0
35
30
25
20
15
10
5
0
-5
-10
-15
Lectu
re of
Mark Lo
uie D
. Lop
ez
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
TORPOR AND ENERGY CONSERVATION
• Estivation, or summer torpor
– Enables animals to survive long periods of
high temperatures and scarce water supplies
• Daily torpor
– Is exhibited by many small mammals and birds
and seems to be adapted to their feeding
patterns
Lectu
re of
Mark Lo
uie D
. Lop
ez
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