1. Basic Principles of Animal Form and Function
Chapter 40
Basic Principles of Animal Form and Function

2. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. How does a jackrabbit keep from overheating?
Figure 40.1 How does a jackrabbit keep from overheating?
For the Discovery Video Human Body, go to Animation and Video Files.

4. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Convergent evolution in fast swimmers
(a) Tuna
Figure 40.2 Convergent evolution in fast swimmers
(b) Penguin
(c) Seal

7. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Contact with the environment
Mouth
Gastrovascular
cavity
Exchange
Exchange
Exchange
Figure 40.3 Contact with the environment
0.15 mm
1.5 mm
(a) Single cell
(b) Two layers of cells

9. Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials.
More complex organisms have highly folded internal surfaces for exchanging materials.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10. Internal exchange surfaces of complex animals
External environment
CO2
Food O2
Mouth
Animal
body
Respiratory
system
Blood
50 µm
0.5 cm
Lung tissue
Nutrients
Cells
Heart
Circulatory
system
10 µm
Interstitial
fluid
Digestive
system
Figure 40.4 Internal exchange surfaces of complex animals
Lining of small intestine
Excretory
system
Kidney tubules
Anus
Unabsorbed
matter (feces)
Metabolic waste products
(nitrogenous waste)

11. Hierarchical Organization of Body Plans
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.
Most animals are composed of specialized cells organized into tissues that have different functions.
Tissues make up organs, which together make up organ systems.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

12. Organ Systems

13. Tissue Structure and Function
Different tissues have different structures that are suited to their functions.
Tissues are classified into four main categories: epithelial, connective, muscle, and nervous.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

14. Epithelial Tissue - Covering & Lining
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).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Structure and function in animal tissues
Epithelial Tissue
Cuboidal
epithelium
Simple
columnar
epithelium
Pseudostratified
ciliated
columnar
epithelium
Stratified
squamous
epithelium
Figure 40.5 Structure and function in animal tissues
Simple
squamous
epithelium

16. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

17. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18. Connective Tissue
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

19. Adipose tissue stores fat for insulation and fuel.
Connective Tissue
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20. Connective Tissue Loose connective tissue Cartilage Fibrous connective
Collagenous fiber
Loose
connective
tissue
Chondrocytes
Cartilage
120 µm
100 µm
Elastic fiber
Chondroitin
sulfate
Nuclei
Fat droplets
Fibrous
connective
tissue
Adipose
tissue
30 µm
150 µm
Figure 40.5 Structure and function in animal tissues
Osteon
White blood cells
Bone
Blood
700 µm
55 µm
Central canal
Plasma
Red blood
cells

21. 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 attached to bones and is responsible for voluntary movement.
Smooth muscle mainly lines internal organs and is responsible for involuntary body activities.
Cardiac muscle is responsible for contraction of the heart.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22. Muscle Tissue Skeletal muscle Cardiac muscle Smooth muscle Multiple
nuclei
Muscle fiber
Sarcomere
Skeletal
muscle
Nucleus
100 µm
Intercalated
disk
50 µm
Cardiac muscle
Figure 40.5 Structure and function in animal tissues
Smooth
muscle
Nucleus
Muscle
fibers
25 µm

23. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Nervous Tissue Neuron 40 µm Axons Blood vessel Dendrites Cell body
Glial cells
Neuron
Figure 40.5 Structure and function in animal tissues
Axons
Blood vessel
15 µm

25. Neuron 40 µm Dendrites Cell body Axon
Figure 40.5 Structure and function in animal tissues
Neuron

26. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. Signaling Stimulus Stimulus Endocrine cell Neuron Axon Signal Hormone
Signal travels
along axon to
a specific
location.
Signal travels
everywhere
via the
bloodstream.
Blood
vessel
Signal
Axons
Figure 40.6 Signaling in the endocrine and nervous systems
Response
Response
(a) Signaling by hormones
(b) Signaling by neurons

28. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. Stimulus Neuron Axon Signal Signal travels along axon to a specific
location.
Signal
Axons
Figure 40.6b Signaling in the endocrine and nervous systems
Response
Signaling by neurons

30. Feedback control loops maintain the internal environment in many animals
Animals manage their internal environment by regulating or conforming to the external environment.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

31. (temperature conformer)40
River otter (temperature regulator) 30
Body temperature (°C) 20
Largemouth bass
(temperature conformer) 10
Figure 40.7 The relationship between body and environmental temperatures in an aquatic temperature regulator and an aquatic temperature conformer 10 20 30 40
Ambient (environmental) temperature (ºC)

32. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

33. Mechanisms of Homeostasis
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. Negative Feedback acts to reverse a trend… To maintain the variable within a narrow range.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. negative feedback Response: Heater turned off Room temperature
decreases
Stimulus:
Control center
(thermostat)
reads too hot
Set
point:
20ºC
Figure 40.8 A nonliving example of negative feedback: control of room temperature
Stimulus:
Control center
(thermostat)
reads too cold
Room
temperature
increases
Response:
Heater
turned on

35. 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. Instead, positive feedback escalates a trend.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

36. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

37. Homeostatic processes for thermoregulation involve form, function, and behavior
Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range.
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

38. Endothermy is more energetically expensive than ectothermy.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

39. (a) A walrus, an endotherm
Figure 40.9 Endothermy and ectothermy
(b) A lizard, an ectotherm

40. Variation in Body Temperature
The body temperature of a poikilotherm varies with its environment, while that of a homeotherm is relatively constant.
Balancing Heat Loss and Gain:
Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation.
Heat regulation in mammals often involves the integumentary system: skin, hair, and nails.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

41. Heat exchange between an organism and its environment
Radiation
Evaporation
Figure Heat exchange between an organism and its environment
Convection
Conduction

42. Mammalian integumentary system
Hair
Epidermis
Sweat
pore
Dermis
Muscle
Nerve
Sweat
gland
Figure Mammalian integumentary system
Hypodermis
Adipose tissue
Blood vessels
Oil gland
Hair follicle

43. Five general adaptations help animals thermoregulate:
Insulation
Circulatory adaptations
Cooling by evaporative heat loss
Behavioral responses
Adjusting metabolic heat production.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

44. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

45. Circulatory Adaptations
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

46. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

47. Countercurrent heat exchangers
Canada goose
Bottlenose
dolphin
Blood flow
Artery
Vein
Vein
Artery
35ºC
33º
Figure Countercurrent heat exchangers
30º
27º
20º
18º
10º 9º
Countercurrent heat exchangers

48. Cooling by Evaporative Heat Loss
Many types of animals lose heat through evaporation of water in sweat = evaporative cooling.
Panting increases the cooling effect in birds and many mammals.
Sweating or bathing moistens the skin, helping to cool an animal down.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

49. Behavioral Responses
Both endotherms and ectotherms use behavioral responses to control body temperature.
Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

50. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

51. O2 consumption (mL O2/hr) per kg
RESULTS
A Burmese python generates heat while incubating eggs.
120
100 80
O2 consumption (mL O2/hr) per kg 60 40
Figure How does a Burmese python generate heat while incubating eggs? 20 5 10 15 20 25 30 35
Contractions per minute

52. Acclimatization in Thermoregulation
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.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

53. Hypothalamus: thermoregulation
Sweat glands secrete sweat, which evaporates, cooling the body.
Thermostat in hypothalamus activates cooling mechanisms.
Hypothalamus: thermoregulation
Blood vessels in skin dilate: capillaries fill; heat radiates from skin.
Body temperature decreases; thermostat shuts off cooling mechanisms.
Increased body temperature
Homeostasis: Internal temperature of 36–38°C
Body temperature increases; thermostat shuts off warming mechanisms.
Decreased body temperature
Figure The thermostatic function of the hypothalamus in human thermoregulation
Blood vessels in skin constrict, reducing heat loss.
Thermostat in hypothalamus activates warming mechanisms.
Skeletal muscles contract; shivering generates heat.

54. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

55. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

56. Bioenergetics of an animal
Organic molecules
in food
Bioenergetics of an animal
External
environment
Animal
body
Digestion and
absorption
Heat
Energy lost
in feces
Nutrient molecules
in body cells
Energy lost in
nitrogenous
waste
Carbon
skeletons
Cellular
respiration
Heat
Figure Bioenergetics of an animal: an overview
ATP
Biosynthesis
Cellular
work
Heat
Heat

57. Quantifying Energy Use
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

58. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

59. Influences on Metabolic Rate
Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm.
Two of these factors are size and activity.
Metabolic rate is inversely related to body size among similar animals.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

60. Relationship of Metabolic Rate to Body Size
103
Elephant
102
Horse
Human 10
Sheep
BMR (L O2/hr) (Iog scale)
Cat
Dog 1
Rat
10–1
Ground squirrel
Shrew
Mouse
Harvest mouse
10–2
10–3
10–2
10–1 1 10
102
103
Body mass (kg) (log scale)
(a) Relationship of BMR to body size 8
Shrew 7 6
Figure The relationship of metabolic rate to body size 5
BMR (L O2/hr) (per kg) 4 3
Harvest mouse 2
Mouse
Sheep
Rat
Human
Elephant 1
Cat
Dog
Ground squirrel
Horse
10–3
10–2
10–1 1 10
102
103
Body mass (kg) (log scale)
(b) Relationship of BMR per kilogram of body mass to body size

61. Activity, Metabolic Rate, and Energy Budgets
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.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

62. from temperate climate
Energy budgets for four animals
Endotherms
Ectotherm
800,000
Reproduction
Basal
(standard)
metabolism
Thermoregulation
Growth
Activity
Annual energy expenditure (kcal/hr)
340,000
8,000
4,000
Figure Energy budgets for four animals
60-kg female human
from temperate climate
4-kg male Adélie penguin
from Antarctica (brooding)
0.025-kg female deer mouse
from temperate
North America
4-kg female eastern
indigo snake

63. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

64. Body temperature and metabolism during hibernation in ground squirrels
Additional metabolism that would be
necessary to stay active in winter
200
Actual
metabolism
Metabolic rate
(kcal per day)
100
Arousals 35
Body
temperature 30 25 20
Temperature (°C) 15 10
Figure Body temperature and metabolism during hibernation in Belding’s ground squirrels 5
Outside
temperature –5
Burrow
temperature
–10
–15
June
August
October
December
February
April

65. 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

66. You should now be able to:
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.
Relate structure with function and identify diagrams of the following animal tissues: epithelial, connective tissue (six types), muscle tissue (three types), and nervous tissue.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

67. Compare and contrast the nervous and endocrine systems.
Define thermoregulation and explain how endotherms and ectotherms manage their heat budgets.
Describe how a countercurrent heat exchanger may function to retain heat within an animal body.
Define bioenergetics and biosynthesis.
Define metabolic rate and explain how it can be determined for animals.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings