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Fig. 40-1
Nice ears, but why so big?
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Overview: Diverse Forms, Common Challenges
• Anatomy is the study of the biological form of an organism
• Physiology is the study of the biological functions an organism performs
• The comparative study of animals reveals that form and function are closely correlated
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Concept 40.1: Animal form and function are correlated at all levels of organization
• Size and shape affect the way an animal interacts with its environment
• Many different animal body plans have evolved and are determined by the genome
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Physical Constraints on Animal Size and Shape
• The ability to perform certain actions depends on an animal’s shape, size, and environment
• Evolutionary convergence reflects different species’ adaptations to a similar environmental challenge
• Physical laws impose constraints on animal size and shape
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Video: GalVideo: Galáápagos Sea Lionpagos Sea Lion
Video: Shark Eating SealVideo: Shark Eating Seal
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Fig. 40-2
(a) Tuna
(b) Penguin
(c) Seal
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Exchange with the Environment
• An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings
• Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes
• A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm
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Video: Hydra Eating DaphniaVideo: Hydra Eating Daphnia
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Fig. 40-3
Exchange
0.15 mm
(a) Single cell
1.5 mm
(b) Two layers of cells
Exchange
Exchange
Mouth
Gastrovascularcavity
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• Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials
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• More complex organisms have highly folded internal surfaces for exchanging materials
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Fig. 40-4
0.5 cmNutrients
Digestivesystem
Lining of small intestine
MouthFood
External environment
Animalbody
CO2 O2
Circulatorysystem
Heart
Respiratorysystem
Cells
Interstitialfluid
Excretorysystem
Anus
Unabsorbedmatter (feces)
Metabolic waste products(nitrogenous waste)
Kidney tubules
10 µm
50 µ
m
Lung tissue
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• In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells
• A complex body plan helps an animal in a variable environment to maintain a relatively stable internal environment
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• Different 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 the organs and cavities within the body
• It contains cells that are closely joined
• The shape of epithelial cells may be cuboidal (like dice), columnar (like bricks on end), or squamous (like floor tiles)
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• The arrangement of epithelial cells may be simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer of cells of varying length)
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Fig. 40-5a
Epithelial Tissue
Cuboidalepithelium
Simplecolumnarepithelium
Pseudostratifiedciliatedcolumnarepithelium
Stratifiedsquamousepithelium
Simplesquamousepithelium
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Fig. 40-5b
Apical surface
Basal surfaceBasal lamina
40 µm
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Connective Tissue
• Connective tissue mainly binds and supports other tissues
• It contains sparsely packed cells scattered throughout an extracellular matrix
• The matrix consists of fibers in a liquid, jellylike, or solid foundation
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• There are three types of connective tissue fiber, all made of protein:
– Collagenous fibers provide strength and flexibility
– Elastic fibers stretch and snap back to their original length
– Reticular fibers join connective tissue to adjacent tissues
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• Connective tissue contains cells, including
– Fibroblasts that secrete the protein of extracellular fibers
– Macrophages that are involved in the immune system
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• In vertebrates, the fibers and foundation combine to form six major types of connective tissue:
– Loose connective tissue binds epithelia to underlying tissues and holds organs in place
– Cartilage is a strong and flexible support material
– Fibrous connective tissue is found in tendons, which attach muscles to bones, and ligaments, which connect bones at joints
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– Adipose tissue stores fat for insulation and fuel
– Blood is composed of blood cells and cell fragments in blood plasma
– Bone is mineralized and forms the skeleton
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Fig. 40-5c
Connective Tissue
Collagenous fiber
Looseconnectivetissue
Elastic fiber12
0 µ
m
Cartilage
Chondrocytes
10
0 µ
m
Chondroitinsulfate
Adiposetissue
Fat droplets
15
0 µ
m
White blood cells
55
µm
Plasma Red bloodcells
Blood
Nuclei
Fibrousconnectivetissue
30
µm
Osteon
Bone
Central canal
70
0 µ
m
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Muscle Tissue
• Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals
• It is divided in the vertebrate body into three types:
– Skeletal muscle, or striated muscle, is responsible for voluntary movement
– Smooth muscle is responsible for involuntary body activities
– Cardiac muscle is responsible for contraction of the heart
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Fig. 40-5j
Muscle Tissue
50 µmSkeletalmuscle
Multiplenuclei
Muscle fiber
Sarcomere
100 µm
Smoothmuscle
Cardiac muscle
Nucleus
Musclefibers
25 µm
Nucleus Intercalateddisk
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Nervous Tissue
• Nervous tissue senses stimuli and transmits signals throughout the animal
• Nervous tissue contains:
– Neurons, or nerve cells, that transmit nerve impulses
– Glial cells, or glia, that help nourish, insulate, and replenish neurons
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Fig. 40-5n
Glial cells
Nervous Tissue
15 µm
Dendrites
Cell body
Axon
Neuron
Axons
Blood vessel
40 µm
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Coordination and Control
• Control and coordination within a body depend on the endocrine system and the nervous system
• The endocrine system transmits chemical signals called hormones to receptive cells throughout the body via blood
• A hormone may affect one or more regions throughout the body
• Hormones are relatively slow acting, but can have long-lasting effects
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Fig. 40-6aStimulus
Endocrinecell
Hormone
Signal travelseverywherevia thebloodstream.
Bloodvessel
Response
(a) Signaling by hormones
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• The nervous system transmits information between specific locations
• The information conveyed depends on a signal’s pathway, not the type of signal
• Nerve signal transmission is very fast
• Nerve impulses can be received by neurons, muscle cells, and endocrine cells
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Fig. 40-6bStimulus
Neuron
AxonSignal
Signal travelsalong axon toa specificlocation.
Signal
Axons
Response
(b) Signaling by neurons
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Concept 40.2: Feedback control loops maintain the internal environment in many animals
• Animals manage their internal environment by regulating or conforming to the external environment
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• A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
• A conformer allows its internal condition to vary with certain external changes
Regulating and Conforming
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Fig. 40-7
River otter (temperature regulator)
Largemouth bass(temperature conformer)
Bo
dy
tem
per
atu
re (
°C)
0 10
10
20
20
30
30
40
40
Ambient (environmental) temperature (ºC)
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Homeostasis
• Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment
• In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level
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• Mechanisms of homeostasis moderate changes in the internal environment
• For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response
• The response returns the variable to the set point
Mechanisms of Homeostasis
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Animation: Positive FeedbackAnimation: Positive Feedback
Animation: Negative FeedbackAnimation: Negative Feedback
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Fig. 40-8Response:Heater turnedoff
Stimulus:Control center(thermostat)reads too hot
Roomtemperaturedecreases
Setpoint:20ºC
Roomtemperature
increases
Stimulus:Control center(thermostat)
reads too cold
Response:Heater turnedon
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Feedback Loops in Homeostasis
• The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to either a normal range or a set point
• Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off
• Positive feedback loops occur in animals, but do not usually contribute to homeostasis
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Alterations in Homeostasis
• Set points and normal ranges can change with age or show cyclic variation
• Homeostasis can adjust to changes in external environment, a process called acclimatization
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Concept 40.3: Homeostatic processes for thermoregulation involve form, function, and behavior
• Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range
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• Endothermic animals generate heat by metabolism; birds and mammals are endotherms
• Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and non-avian reptiles
Endothermy and Ectothermy
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• In general, ectotherms tolerate greater variation in internal temperature, while endotherms are active at a greater range of external temperatures
• Endothermy is more energetically expensive than ectothermy
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Fig. 40-9
(a) A walrus, an endotherm
(b) A lizard, an ectotherm
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Variation in Body Temperature
• The body temperature of a poikilotherm varies with its environment, while that of a homeotherm is relatively constant
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Balancing Heat Loss and Gain
• Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation
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Fig. 40-10
Radiation Evaporation
Convection Conduction
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• Heat regulation in mammals often involves the integumentary system: skin, hair, and nails
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Fig. 40-11
Epidermis
Dermis
Hypodermis
Adipose tissue
Blood vessels
Hair
Sweatpore
Muscle
Nerve
Sweatgland
Oil glandHair follicle
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• Five general adaptations help animals thermoregulate:
– Insulation
– Circulatory adaptations
– Cooling by evaporative heat loss
– Behavioral responses
– Adjusting metabolic heat production
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Insulation
• Insulation is a major thermoregulatory adaptation in mammals and birds
• Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment
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• Regulation of blood flow near the body surface significantly affects thermoregulation
• Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin
• 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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• The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange
• Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions
• Countercurrent heat exchangers are an important mechanism for reducing heat loss
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Fig. 40-12
Canada goose Bottlenosedolphin
Artery
Artery
Vein Vein
Blood flow
33º35ºC
27º30º
18º20º
10º 9º
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• Some bony fishes and sharks also use countercurrent heat exchanges
• 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 evaporation of water in sweat
• Panting increases the cooling effect in birds and many mammals
• Sweating or bathing moistens the skin, helping to cool an animal down
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• Both endotherms and ectotherms use behavioral responses to control body temperature
• Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat
Behavioral Responses
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Fig. 40-13
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Adjusting Metabolic Heat Production
• Some animals can regulate body temperature by adjusting their rate of metabolic heat production
• Heat production is increased by muscle activity such as moving or shivering
• Some ectotherms can also shiver to increase body temperature
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Fig. 40-14
RESULTS
Contractions per minute
O2
con
sum
pti
on
(m
L O
2/h
r) p
er k
g
00
20
2015105 25 30 35
40
60
80
100
120
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Fig. 40-15
PREFLIGHT PREFLIGHTWARM-UP
FLIGHT
Thorax
Abdomen
Time from onset of warm-up (min)
Te
mp
era
ture
(ºC
)
0 2 4
25
30
35
40
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• Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes
• When temperatures are subzero, some ectotherms produce “antifreeze” compounds to prevent ice formation in their cells
Acclimatization in Thermoregulation
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Physiological Thermostats and Fever
• Thermoregulation is controlled by a region of the brain called the hypothalamus
• The hypothalamus triggers heat loss or heat generating mechanisms
• Fever is the result of a change to the set point for a biological thermostat
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Fig. 40-16Sweat glands secrete sweat, which evaporates, cooling the body.
Thermostat in hypothalamus activates cooling mechanisms.
Blood vessels in skin dilate: capillaries fill; heat radiates from skin.
Increased body temperature
Decreased body temperature
Thermostat in hypothalamus activates warming mechanisms.
Blood vessels in skin constrict, reducing heat loss.
Skeletal muscles contract; shivering generates heat.
Body temperature increases; thermostat
shuts off warming mechanisms.
Homeostasis: Internal temperature
of 36–38°C
Body temperature decreases; thermostat
shuts off cooling mechanisms.
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Concept 40.4: Energy requirements are related to animal size, activity, and environment
• Bioenergetics is the overall flow and transformation of energy in an animal
• It determines how much food an animal needs and relates to an animal’s size, activity, and environment
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Energy Allocation and Use
• Animals harvest chemical energy from food
• Energy-containing molecules from food are usually used to make ATP, which powers cellular work
• After the needs of staying alive are met, remaining food molecules can be used in biosynthesis
• Biosynthesis includes body growth and repair, synthesis of storage material such as fat, and production of gametes
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Fig. 40-17
Organic moleculesin foodExternal
environment
Animalbody Digestion and
absorption
Nutrient moleculesin body cells
Carbonskeletons
Cellularrespiration
ATP
Heat
Energy lostin feces
Energy lost innitrogenouswaste
Heat
Biosynthesis
Heat
Heat
Cellularwork
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• Metabolic rate is the amount of energy an animal uses in a unit of time
• One way to measure it is to determine the amount of oxygen consumed or carbon dioxide produced
Quantifying Energy Use
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Fig. 40-18
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Minimum Metabolic Rate and Thermoregulation
• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature
• Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature
• Both rates assume a nongrowing, fasting, and nonstressed animal
• Ectotherms have much lower metabolic rates than endotherms of a comparable size
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• Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm
• Two of these factors are size and activity
Influences on Metabolic Rate
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Size and Metabolic Rate
• Metabolic rate per gram is inversely related to body size among similar animals
• Researchers continue to search for the causes of this relationship
• The higher metabolic rate of smaller animals leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood volume, compared with a larger animal
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Fig. 40-19a
Shrew
Harvest mouseMouse
Ground squirrel
Rat
Cat Dog
Sheep
Human
Horse
Elephant
Body mass (kg) (log scale)
BM
R (
L O
2/h
r) (
log
sc
ale
)
(a) Relationship of BMR to body size
10–3 10–210–2
10–1
10–1
1
1
10 102 103
10
102
103
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Fig. 40-19b
10310210110–110–210–30
1
2
3
4
5
6
7
8
Body mass (kg) (log scale)
(b) Relationship of BMR per kilogram of body mass to body size
BM
R (
L O
2/h
r) (
per
kg
)Shrew
Harvest mouse
Mouse
Rat
Ground squirrel
Cat
Sheep
DogHuman
Horse
Elephant
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• Activity greatly affects metabolic rate for endotherms and ectotherms
• In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity
Activity and Metabolic Rate
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• Different species use energy and materials in food in different ways, depending on their environment
• Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, and reproduction
Energy Budgets
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Fig. 40-20a
An
nu
al e
ne
rgy
ex
pe
nd
itu
re (
kc
al/h
r)
60-kg female humanfrom temperate climate
800,000Basal(standard)metabolism
ReproductionThermoregulation
Growth
Activity
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Fig. 40-20b
Reproduction
Thermoregulation
Activity
Basal(standard)metabolism
4-kg male Adélie penguinfrom Antarctica (brooding)
An
nu
al e
ner
gy
exp
end
itu
re (
kcal
/yr)
340,000
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Fig. 40-20c
Reproduction
Thermoregulation
Basal(standard)metabolism
Activity
4,000
0.025-kg female deer mousefrom temperateNorth America
An
nu
al e
ner
gy
exp
end
itu
re (
kcal
/yr)
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Fig. 40-20d
Reproduction
Growth
Activity
Basal(standard)metabolism
4-kg female easternindigo snake
8,000
An
nu
al e
ner
gy
exp
end
itu
re (
kcal
/yr)
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Torpor and Energy Conservation
• Torpor is a physiological state in which activity is low and metabolism decreases
• Torpor enables animals to save energy while avoiding difficult and dangerous conditions
• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity
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Fig. 40-21
Additional metabolism that would benecessary to stay active in winterActual
metabolism
Arousals
Bodytemperature
Outsidetemperature Burrow
temperature
Met
abo
lic
rate
(kca
l p
er d
ay)
Tem
per
atu
re (
°C)
June August October December February April–15
–10
–5
0
5
15
10
25
20
35
30
0
100
200
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• 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 adapted to feeding patterns
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You should now be able to:
1. Distinguish among the following sets of terms: collagenous, elastic, and reticular fibers; regulator and conformer; positive and negative feedback; basal and standard metabolic rates; torpor, hibernation, estivation, and daily torpor
2. Relate structure with function and identify diagrams of the following animal tissues: epithelial, connective tissue (six types), muscle tissue (three types), and nervous tissue
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3. Compare and contrast the nervous and endocrine systems
4. Define thermoregulation and explain how endotherms and ectotherms manage their heat budgets
5. Describe how a countercurrent heat exchanger may function to retain heat within an animal body
6. Define bioenergetics and biosynthesis
7. Define metabolic rate and explain how it can be determined for animals
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