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Chapter 40: Animal Form and
Function
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• Animals inhabit almost every part of the
biosphere
• Despite their amazing diversity
– All animals face a similar set of problems,
including how to nourish themselves
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Form and function are closely correlated
Figure 40.1
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• Natural selections select for what works best
among the available variations in a population
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• Evolutionary convergence
– Independent adaptation to a similar
environmental challenge
(a) Tuna
(b) Shark
(c) Penguin
(d) Dolphin
Figure 40.2a–e
(e) Seal
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Exchange with the Environment
• Occurs as substances dissolved in the
aqueous medium
transported across membranes
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• Single-celled protist has a sufficient surface
area of plasma membrane to service its entire
volume of cytoplasm
Diffusion
Figure 40.3a
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(a) Single cell
• Multicellular organisms with body walls that are
only two cells thick  facilitate diffusion
Mouth
Gastrovascular
cavity
Diffusion
Diffusion
Figure 40.3b
(b) Two cell layers
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• Organisms with complex body plans
–  highly folded internal surfaces (lg. surface area)
specialized for exchanging materials
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External environment
Mouth
Food
CO2
O2
Respiratory
system
0.5 cm
A microscopic view of the lung reveals
that it is much more spongelike than
balloonlike. This construction provides
an expansive wet surface for gas
exchange with the environment (SEM).
Cells
Heart
Nutrients
50 µm
Animal
body
Circulatory
system
10 µm
Interstitial
fluid
Digestive
system
Excretory
system
The lining of the small intestine, a digestive organ, is elaborated with fingerlike
projections that expand the surface area
for nutrient absorption (cross-section, SEM).
Anus
Unabsorbed
matter (feces)
Figure 40.4
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Metabolic waste
products (urine)
Inside a kidney is a mass of microscopic
tubules that exhange chemicals with
blood flowing through a web of tiny
vessels called capillaries (SEM).
• Animal form and function are correlated at all
levels of organization
– cells
– tissues
– organs
– organ systems
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Tissue Structure and Function
• 4 main categories
– Epithelial, connective, muscle, and nervous
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Epithelial Tissue
• Covers the outside of the body and lines
organs and cavities within the body
– cells are closely joined
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Epithelial tissue
A simple
columnar
epithelium
A stratified
columnar
A pseudostratified
epithelium
ciliated columnar
epithelium
Stratified squamous epithelia
Cuboidal epithelia
Simple squamous epithelia
Basement membrane
Figure 40.5
40 µm
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Connective Tissue
• Bind and supports other tissues
– sparsely packed cells scattered throughout an
extracellular matrix
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CONNECTIVE TISSUE
• Connective tissue
100 µm
Chondrocytes
Chondroitin
sulfate
Loose connective tissue
100 µm
Collagenous
fiber
Elastic
fiber
Cartilage
Adipose tissue
Fibrous connective tissue
Fat droplets
150 µm
Nuclei
30 µm
Blood
Bone
Central
canal
Red blood cells
White blood cell
Osteon
Figure 40.5
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700 µm
Plasma
55 µm
Muscle Tissue
• Composed of long cells called muscle fibers,
contract in response to nerve signals
– 3 types: skeletal, cardiac, and smooth
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Nervous Tissue
• Senses stimuli and transmits signals
throughout the animal
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• Muscle and nervous tissue
MUSCLE TISSUE
100 µm
Skeletal muscle
Multiple
nuclei
Muscle fiber
Sarcomere
Cardiac muscle
Nucleus Intercalated
disk
Smooth muscle
50 µm
Nucleus
Muscle
fibers
25 µm
NERVOUS TISSUE
Process
Neurons
Cell body
Nucleus
Figure 40.5
50 µm
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Neurons
Dendrites
Cell body
Nucleus
Synapse
Signal
Axon direction
Axon hillock
Presynaptic cell
Postsynaptic cell
Myelin sheath
Figure 48.5
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Synaptic
terminals
• In some organs tissues are arranged in layers
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.
Serosa. External to the muscularis is the serosa,
a thin layer of connective and epithelial tissue.
Figure 40.6
0.2 mm
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• Organ systems in mammals
Table 40.1
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• Organisms require chemical energy for
– Growth, repair, physiological processes,
regulation, and reproduction
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Bioenergetics
• Flow of energy through an animal
– Limits the animal’s behavior, growth, and
reproduction, how much food it needs
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Energy Sources and Allocation
• Chemical energy from food food digested 
molecules generate ATP  powers cellular
work
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• Metabolic needs and biosynthesis
Organic molecules
in food
External
environment
Animal
body
Digestion and
absorption
Heat
Nutrient molecules
in body cells
Carbon
skeletons
Cellular
respiration
Energy
lost in
feces
Energy
lost in
urine
Heat
ATP
Biosynthesis:
growth,
storage, and
reproduction
Figure 40.7
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Heat
Cellular
work
Heat
• Measuring metabolic rate by amount of oxygen
consumed or carbon dioxide produced
(a)
Figure 40.8a, b
This photograph shows a ghost crab in a
respirometer. Temperature is held constant in the
chamber, with air of known O2 concentration flowing 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.
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(b) Similarly, the metabolic rate of a man
fitted with a breathing apparatus is
being monitored while he works out
on a stationary bike.
• Birds and mammals are endothermic
– bodies warmed by heat generated by
metabolism
– high metabolic rates
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• Amphibians, reptiles other than birds, and
………..Daphnia are ectothermic
– gain their heat from external sources
– lower metabolic rates
– Q 10
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Size and Metabolic Rate
• Metabolic rate inversely related to body size
among similar animals
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Activity and Metabolic Rate
• Basal metabolic rate (BMR)
– Metabolic rate of an endotherm at rest
• Standard metabolic rate (SMR)
– Metabolic rate of an ectotherm at rest
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• Animal’s maximum possible metabolic rate is
inversely related to the duration of the activity
500
A
100
H
A
(kcal/min; log scale)
Maximum metabolic rate
A = 60-kg alligator
H
H = 60-kg human
50
H
10
H
H
5
A
1
A
A
0.5
0.1
1
second
1
minute
1
hour
Time interval
Key
Figure 40.9
Existing intracellular ATP
ATP from glycolysis
ATP from aerobic respiration
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1
day
1
week
Energy use
Annual energy expenditure (kcal/yr)
Endotherms
Ectotherm
Reproduction
800,000
Basal
metabolic
rate
Temperature
regulation costs
Growth
Activity
costs
340,000
8,000
4,000
4-kg male Adélie penguin
from Antarctica (brooding)
60-kg female human
from temperate climate
(b)
4-kg female python
from Australia
438
Human
233
Deer mouse
Python
Adélie
(kcal/kg•day)
Energy expenditure per unit mass
(a) Total annual energy expenditures
0.025-kg female deer mouse
from temperate
North America
penguin
36.5
5.5
Energy expenditures per unit mass (kcal/kg•day)
Figure 40.10a, b
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• Animals regulate their internal environment
within relatively narrow limits
• Homeostasis: balance between external
changes and the animal’s internal control
mechanisms that oppose the changes
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• Regulator
– Uses internal control mechanisms to moderate
internal change in the face of external,
environmental fluctuation
• Conformer
– Allows its internal condition to vary with certain
external changes
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Homeostatic control system
• 3 functional components
– receptor, control center, and effector
Response
No heat
produced
Heater
turned
off
Room
temperature
decreases
Too
hot
Set
point
Too
cold
Set
point
Set point
Control center:
thermostat
Room
temperature
increases
Heater
turned
on
Response
Figure 40.11
Heat
produced
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• Homeostatic control systems function by
negative feedback
– buildup of the end product shuts the system off
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• Positive feedback
– change in some variable that amplify the
change
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• Thermoregulation
– animals maintain an internal temperature
within a tolerable range
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Ectotherms
• Tolerate greater variation in internal temperature
40
than endotherms
Body temperature (°C)
River otter (endotherm)
30
20
Largemouth bass (ectotherm)
10
0
Figure 40.12
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10
20
30
40
Ambient (environmental) temperature (°C)
Endothermy
• Energetically more expensive than ectothermy
– Buffers animals’ internal temperatures against
external fluctuations
– High level of aerobic metabolism
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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.
Figure 40.13
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
Conduction is the direct transfer of thermal motion (heat)
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.
between molecules of objects in direct contact with each
other, as when a lizard sits on a hot rock.
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Insulation
• Thermoregulatory adaptation in mammals and
birds
– Reduces the flow of heat between an animal
and its environment
– e.g. feathers, fur, or blubber
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• Mammal integumentary system
– Acts as insulating material
Hair
Epidermis
Sweat
pore
Muscle
Dermis
Nerve
Sweat
gland
Hypodermis
Adipose tissue
Figure 40.14
Blood vessels
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Oil gland
Hair follicle
Circulatory adaptations
• Vasodilation
– Blood flow in the skin increases, facilitating
heat loss
• Vasoconstriction
– Blood flow in the skin decreases, lowering heat
loss
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• Countercurrent heat exchangers  reduce
heat loss
1
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.
Canada
goose
Pacific
bottlenose
dolphin
2
Artery
35°C
33°
30º
1
27º
20º
18º
10º
9º
2
Figure 40.15
Vein
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
3 direction.
opposite
1
Blood flow
Vein
Artery
3
3
2
3 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.
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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.
• Some bony fishes and sharks also possess
countercurrent heat exchangers
21º
25º 23º
27º
(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.
Figure 40.16a, b
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29º
31º
Body cavity
Skin
Artery
Vein
Blood
vessels
in gills
Heart
Capillary
network within
muscle
Artery and
vein under Dorsal aorta
the skin
• Endothermic insects
– countercurrent heat exchangers maintain a
high temperature in the thorax
Figure 40.17
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Cooling by Evaporative Heat Loss
• Lose heat through the evaporation of water in
sweat
• Panting cools bodies
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• Bathing cools animal
Figure 40.18
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• Certain postures enable animals to minimize or
maximize their absorption of heat from the sun
Figure 40.19
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• Flying insects use shivering to warm up before
taking flight
PREFLIGHT
PREFLIGHT
FLIGHT
WARMUP
Temperature (°C)
40
Thorax
35
30
Abdomen
25
0
2
Time from onset of warmup (min)
Figure 40.20
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4
Thermoregulation
• The hypothalamus functions as
a thermostat
Sweat glands secrete
sweat that evaporates,
cooling the body.
Thermostat in
hypothalamus
activates cooling
mechanisms.
Blood vessels
in skin dilate:
capillaries fill
with warm blood;
heat radiates from
skin surface.
Increased body
temperature (such
as when exercising
or in hot
surroundings)
Body temperature
decreases;
thermostat
shuts off cooling
mechanisms.
Homeostasis:
Internal body temperature
of approximately 36–38C
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.
Figure 40.21
Skeletal muscles rapidly
contract, causing shivering,
which generates heat.
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Thermostat in
hypothalamus
activates
warming
mechanisms.
Acclimatization
• Animals can adjust to a new range of
environmental temperatures over a period of
days or weeks
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Torpor
• Adaptation that enables animals to save
energy while avoiding difficult and dangerous
conditions
– physiological state of low activity and
metabolism
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• Hibernation (long-term torpor)
Additional metabolism that would be
necessary to stay active in winter
Figure 40.22
Metabolic rate
(kcal per day)
200
Actual
metabolism
100
0
Arousals
35
Body
temperature
Temperature (°C)
30
25
20
15
10
5
0
Outside
temperature
-5
Burrow
temperature
-10
-15
June
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August
October
December
February
April
• Estivation, or summer torpor
– survive long periods of high temperatures and
scarce water supplies
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