Download File

Chapter 40
Basic Principles of Animal
Form and Function
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Form and function are correlated.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
40.1
• Physical factors (strength, diffusion, movement,
heat exchange) limit the evolution of animal
forms (size and shape).
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Animals must exchange materials with their
environment.
• Most animals have branched/folded surfaces
for this purpose.
• Fluid is key to cellular exchanges.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Benefits of a complex body plan:
• External skeleton protects against predators
• Sensory organs provide info.
• Internal digestive organs allow for the gradual
breakdown of food and a controlled release of
energy
• Filtration systems adjust the composition of
internal fluids
• **These features allow for homeostasis!**
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
External environment
Mouth
Food
CO2
O2
Respiratory
system
0.5 cm
Cells
Heart
Nutrients
Circulatory
system
50 µm
Animal
body
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).
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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).
Organism Organization
• cells  tissues  organs  organ systems
• 4 main categories of animal tissue:
– Epithelial tissue
– Connective tissue
– Muscle tissue
– Nervous tissue
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Control and coordination of the body
• **allows for homeostasis!**
• Nervous system
– immediate and rapid responses to the environment
– locomotion
– behavior
• Endocrine system
– Growth and development
– Reproduction
– Metabolism
– Digestion
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
40.2
• Homeostasis is maintained using signal
transduction pathways ( a stimulus is detected
by a sensor and a response is produced).
• Feedback Loops
– Negative feedback ( the response reduces the
stimulus)
– Positive feedback (amplifies the stimulus)
*Does not usually contribute to homeostasis.*
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Alterations in the mechanisms of feedback
often result in deleterious consequences.
– Diabetes and insulin
– Dehydration and antidiuretic hormone
– Grave’s disease
– Blood clotting
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
40.3 Homeostatic processes for thermoregulation (form and function working together)
Thermoregulation – maintenance of an internal
body temperature (within an optimal range)
Why is thermoregulation important?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Endothermic Organisms
• Warmed by the heat from metabolism
• Can maintain stable body temperatures during
large environmental temperature fluctuations
• Ex. birds, mammals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecothermic Organisms
• Gain heat from external sources
• Need to consume less food than endotherms of
equal size
• Tolerate larger fluctuations in internal
temperatures
• Adjust their body temperatures via behavior
• Ex. amphibians, lizards, turtles, most
invertebrates
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Thermoregulatory adaptations
• Insulation (hair, feathers, layers of fat)
• Cooling by evaporative heat loss
• Circulatory adaptations
– Vasodilation and Vasoconstriction
– Countercurrent exchange
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Many marine mammals and birds
– Have arrangements of blood vessels called
countercurrent heat exchangers that are important
for reducing 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
Artery
1
35°C
30º
2 Near the end of the leg or flipper, where
arterial blood has been cooled to far below
Vein
the animal’s core temperature, the artery
can still transfer heat to the even colder
3
blood of an adjacent vein. The venous blood
33°
continues to absorb heat as it passes warmer
and warmer arterial blood traveling in the
opposite direction.
27º
20º
18º
10º
9º
2
Pacific
bottlenose
dolphin
1
3
Blood flow
3
Vein
Artery
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.
Figure 40.15
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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.
• Countercurrent exchange occurs in aquatic as
well as terrestrial organisms.
• This reflects common ancestry.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
With a partner…
• Choose an organism, and describe it’s
thermoregulatory mechanisms for maintaining
homeostasis.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
40.4
• Bioenergetics
– Overall flow and transformation of energy in an
animal
– Determines nutritional needs
– Related to animal size, activity & environment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Metabolic rate
– The amount of energy an animal uses in a unit
of time
– Can be determined by:
• Rate of heat loss
• Amount of oxygen consumed
• Amount of carbon dioxide produced
• Rate of food consumption
• Energy content of food
• Chemical energy lost in waste products
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
What influences metabolic rate?
• Size
• Activity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
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
• Estivation, or summer torpor
– Enables animals to survive long periods of
high temperatures and scarce water supplies
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Energy conservation
• Describe the physiological changes that take
place in an organism during torpor.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Overview: Diverse Forms, Common
Challenges
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The comparative study of animals
– Reveals that form and function are closely
correlated
Figure 40.1
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Natural selection can fit structure, anatomy, to
function, physiology
– By selecting, over many generations, what
works best among the available variations in a
population
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Concept 40.1: Physical laws and the
environment constrain animal size and shape
• Physical laws and the need to exchange
materials with the environment
– Place certain limits on the range of animal
forms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Physical Laws and Animal Form
• The ability to perform certain actions
– Depends on an animal’s shape and size
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Evolutionary convergence
– Reflects different species’ independent
adaptation to a similar environmental challenge
(a) Tuna
(b) Shark
(c) Penguin
(d) Dolphin
Figure 40.2a–e
(e) Seal
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Exchange with the Environment
• An 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A single-celled protist living in water
– Has a sufficient surface area of plasma
membrane to service its entire volume of
cytoplasm
Diffusion
Figure 40.3a
(a) Single cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Figure 40.3b
(b) Two cell layers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Organisms with more complex body plans
– Have highly folded internal surfaces specialized
for exchanging materials
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
External environment
Mouth
Food
CO2
O2
Respiratory
system
0.5 cm
Cells
Heart
Nutrients
Circulatory
system
50 µm
Animal
body
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).
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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).
• Concept 40.2: Animal form and function are
correlated at all levels of organization
• Animals are composed of cells
• Groups of cells with a common structure and
function
– Make up tissues
• Different tissues make up organs
– Which together make up organ systems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Tissue Structure and Function
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Epithelial Tissue
• Epithelial tissue
– Covers the outside of the body and lines
organs and cavities within the body
– Contains cells that are closely joined
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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 simple
columnar
epithelium
A stratified columnar
epithelium
A pseudostratified
ciliated columnar
epithelium
Stratified squamous epithelia
Cuboidal epithelia
Simple squamous epithelia
Basement membrane
Figure 40.5
40 µm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Connective Tissue
• Connective tissue
– Functions mainly to bind and support other
tissues
– Contains sparsely packed cells scattered
throughout an extracellular matrix
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CONNECTIVE TISSUE
• Connective tissue
100 µm
Chondrocytes
Chondroitin
sulfate
100 µm
Collagenous
fiber
Elastic
fiber
Cartilage
Loose connective tissue
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
700 µm
Plasma
55 µm
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nervous Tissue
• Nervous tissue
– Senses stimuli and transmits signals
throughout the animal
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Organs and Organ Systems
• In all but the simplest animals
– Different tissues are organized into organs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In some organs
– The 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Representing a level of organization higher
than organs
– Organ systems carry out the major body
functions of most animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Organ systems in mammals
Table 40.1
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Concept 40.3: 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Bioenergetics
• The flow of energy through an animal, its
bioenergetics
– Ultimately limits the animal’s behavior, growth,
and reproduction
– Determines how much food it needs
• Studying an animal’s bioenergetics
– Tells us a great deal about the animal’s
adaptations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Energy Sources and Allocation
• Animals harvest chemical energy
– From the food they eat
• Once food has been digested, the energycontaining molecules
– Are usually used to make ATP, which powers
cellular work
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• After the energetic needs of staying alive are met
– Any remaining molecules from food can be used
in 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Heat
Cellular
work
Heat
Quantifying Energy Use
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• One way to measure metabolic rate
– Is to determine the amount of oxygen consumed
or carbon dioxide produced by an organism
Figure 40.8a,
(a) 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
b at a constant speed as measurements are made.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
(b) Similarly, the metabolic rate of a man
fitted with a breathing apparatus is
being monitored while he works out
on a stationary bike.
Bioenergetic Strategies
• An animal’s metabolic rate
– Is closely related to its bioenergetic strategy
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Birds and mammals are mainly endothermic,
meaning that
– Their bodies are warmed mostly by heat
generated by metabolism
– They typically have higher metabolic rates
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Stem Elongation
• Amphibians and reptiles other than birds are
ectothermic, meaning that
– They gain their heat mostly from external
sources
– They have lower metabolic rates
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Influences on Metabolic Rate
• The metabolic rates of animals
– Are affected by many factors
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Size and Metabolic Rate
• Metabolic rate per gram
– Is inversely related to body size among similar
animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Activity and Metabolic Rate
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In general, an animal’s maximum possible
metabolic rate
– Is inversely related to the duration of the activity
500
Maximum metabolic rate
(kcal/min; log scale)
A = 60-kg alligator
100
A H
A 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
Existing intracellular ATP
Figure 40.9
ATP from glycolysis
ATP from aerobic respiration
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1
day
1
week
Energy Budgets
• Different species of animals
– Use the energy and materials in food in
different ways, depending on their environment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• An animal’s use of energy
– Is partitioned to BMR (or SMR), activity,
homeostasis, growth, and reproduction
Annual energy expenditure (kcal/yr)
Endotherms
Activity 340,000
costs
8,000
4,000
Energy expenditure per unit mass
(kcal/kg•day)
60-kg female human
from temperate climate
(a) Total annual energy expenditures
Figure 40.10a, b
Ectotherm
800,000 BasalReproduction Temperature
regulation costs
metabolic
rate
Growth
4-kg male Adélie penguin
from Antarctica (brooding)
0.025-kg female deer mouse 4-kg female python
from temperate
from Australia
North America
438
Human
233
Deer mouse
(b) Energy expenditures per unit mass (kcal/kg•day)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Python
Adélie penguin
36.5
5.5
• Concept 40.4: Animals regulate their internal
environment within relatively narrow limits
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Regulating and Conforming
• Regulating and conforming
– Are two extremes in how animals cope with
environmental fluctuations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mechanisms of Homeostasis
• Mechanisms of homeostasis
– Moderate changes in the internal environment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A homeostatic control system has three
functional components
– A receptor, a control center, and an 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Most homeostatic control systems function by
negative feedback
– Where buildup of the end product of the
system shuts the system off
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A second type of homeostatic control system is
positive feedback
– Which involves a change in some variable that
triggers mechanisms that amplify the change
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Concept 40.5: 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ectotherms and Endotherms
• Ectotherms
– Include most invertebrates, fishes, amphibians,
and non-bird reptiles
• Endotherms
– Include birds and mammals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In general, ectotherms
– Tolerate greater variation in internal temperature
than endotherms
40
Body temperature (°C)
River otter (endotherm)
30
20
Largemouth bass (ectotherm)
10
0
Figure 40.12
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
10
20
30
40
Ambient (environmental) temperature (°C)
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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.
Figure 40.13
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.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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.
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.
Balancing Heat Loss and Gain
• Thermoregulation involves physiological and
behavioral adjustments
– That balance heat gain and loss
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In mammals, the integumentary system
– Acts as insulating material
Hair
Epidermis
Sweat
pore
Muscle
Dermis
Nerve
Sweat
gland
Hypodermis
Adipose tissue
Figure 40.14
Blood vessels
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Oil gland
Hair follicle
Circulatory Adaptations
• Many endotherms and some ectotherms
– Can alter the amount of blood flowing between
the body core and the skin
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In vasodilation
– Blood flow in the skin increases, facilitating
heat loss
• In vasoconstriction
– Blood flow in the skin decreases, lowering heat
loss
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Many marine mammals and birds
– Have arrangements of blood vessels called
countercurrent heat exchangers that are important
for reducing 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
Artery
1
35°C
30º
2 Near the end of the leg or flipper, where
arterial blood has been cooled to far below
Vein
the animal’s core temperature, the artery
can still transfer heat to the even colder
3
blood of an adjacent vein. The venous blood
33°
continues to absorb heat as it passes warmer
and warmer arterial blood traveling in the
opposite direction.
27º
20º
18º
10º
9º
2
Pacific
bottlenose
dolphin
1
3
Blood flow
3
Vein
Artery
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.
Figure 40.15
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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 specialized 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
29º
31º
Body cavity
Skin
Artery
Vein
Blood
vessels
in gills
Heart
Capillary
network within
muscle
Artery and
vein under Dorsal aorta
the skin
• Many endothermic insects
– Have countercurrent heat exchangers that help
maintain a high temperature in the thorax
Figure 40.17
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cooling by Evaporative Heat Loss
• Many types of animals
– Lose heat through the evaporation of water in
sweat
– Use panting to cool their bodies
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Bathing moistens the skin
– Which helps to cool an animal down
Figure 40.18
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Behavioral Responses
• Both endotherms and ectotherms
– Use a variety of behavioral responses to
control body temperature
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Some terrestrial invertebrates
– Have certain postures that enable them to
minimize or maximize their absorption of heat
from the sun
Figure 40.19
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Adjusting Metabolic Heat Production
• Some animals can regulate body temperature
– By adjusting their rate of metabolic heat
production
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Many species of flying insects
– Use shivering to warm up before taking flight
PREFLIGHT
Temperature (°C)
40
PREFLIGHT
WARMUP
FLIGHT
Thorax
35
30
Abdomen
25
0
2
Time from onset of warmup (min)
Figure 40.20
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4
Feedback Mechanisms in Thermoregulation
• Mammals regulate their body temperature
– By a complex negative feedback system that
involves several organ systems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In humans, a specific part of the brain, the
hypothalamus
Sweat glands secrete
sweat that evaporates,
cooling the body.
Thermostat in
hypothalamus
activates cooling
mechanisms.
– Contains a group of nerve
cells that function as
a thermostat
Increased body
temperature (such
as when exercising
or in hot
surroundings)
Blood vessels
in skin dilate:
capillaries fill
with warm blood;
heat radiates from
skin surface.
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Skeletal muscles rapidly
contract, causing shivering,
which generates heat.
Thermostat in
hypothalamus
activates
warming
mechanisms.
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Acclimatization may involve cellular
adjustments
– Or in the case of birds and mammals,
adjustments of insulation and metabolic heat
production
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
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
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
August
October
December
February
April
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings