Chapter 40:
Basic Principles of Animal
Form & Function
Rob Swatski
Associate Professor of Biology
HACC – York Campus
1
Exchange with the Environment
• An animal’s size & shape
directly affect how it
exchanges energy & materials
with its envi...
Multicellular
organisms with a
sac body plan have
body walls that are
only 2 cells thick,
which facilitates
diffusion

3
More complex organisms have highly folded internal
surfaces for exchanging materials
External environment
CO2
Food
O2
Mout...
Epithelial Tissue
Cuboidal
epithelium

Simple
columnar
epithelium

Pseudostratified
ciliated
columnar
epithelium
Stratifie...
Connective Tissue
Loose
connective
tissue

Chondrocytes

Cartilage

Elastic fiber

Chondroitin
sulfate

Nuclei

100 µm

12...
Muscle Tissue
Multiple
nuclei
Muscle fiber
Sarcomere

Skeletal
muscle

Nucleus

100 µm

Intercalated
disk

50 µm

Cardiac ...
Nervous Tissue
40 µm
Dendrites
Cell body

Glial cells

Axon

Neuron
Axons
Blood vessel
15 µm

8
Coordination and Control
• Depends on both the endocrine & nervous systems
• The endocrine system: transmits chemical sign...
Stimulus
Endocrine

cell

Hormone
Signal travels
everywhere

via the
bloodstream.

(a) Signaling by hormones

Blood
vessel...
• The nervous system: transmits information
between specific locations
• The information conveyed depends on a nerve
signa...
Stimulus

Neuron
Axon

Signal
Signal travels
along axon to
a specific
location.

Signal
Axons

Response

(b) Signaling by ...
Feedback Control Loops
• Animals manage their internal environment by
regulating or conforming to the external
environment...
40

Body temperature (°C)

River otter (temperature regulator)

30

20
Largemouth bass
(temperature conformer)

10

0

10
...
Homeostasis
• Organisms use homeostasis to maintain a “steady
state” (internal balance) regardless of external
environment...
Mechanisms of Homeostasis
• Moderate changes in the internal environment

• For a given variable, fluctuations above or be...
Response:
Heater
turned
off

Room
temperature
decreases

Stimulus:
Control center
(thermostat)
reads too hot

Set
point:
2...
Homeostasis

Response/effector
Stimulus:
Perturbation/stress
Control center

Sensor/receptor
18
Feedback Loops in Homeostasis
• The dynamic equilibrium of most homeostasis is
maintained by negative feedback loops
- hel...
Alterations in Homeostasis
• Set points & normal ranges can change with age or
show cyclic variation
• Homeostasis can adj...
Thermoregulation: process where animals maintain an
internal temperature within a tolerable range
• Ectothermic animals: g...
• Ectotherms generally tolerate more internal
temperature variations
• Endotherms are active at a greater range of
externa...
Variation in Body Temperature
• Poikilotherm: body temperature varies with its
environment
• Homeotherm: body temperature ...
Balancing Heat Loss and Gain
Organisms exchange heat by 4 physical
processes:

Conduction
Convection
Radiation
Evaporation...
Radiation

Convection

Evaporation

Conduction

25
Heat regulation in mammals often involves the integumentary
system: skin, hair, & nails

Hair
Epidermis

Sweat
pore
Muscle...
5 general adaptations help animals
thermoregulate:
– Insulation
– Circulatory adaptations
– Cooling by evaporative heat lo...
Insulation
Major thermoregulatory adaptation in mammals & birds

Skin, feathers, fur, & blubber reduce heat flow between
a...
Circulatory Adaptations
• Regulation of blood flow near the body surface
significantly affects thermoregulation
• Many end...
• The arrangement of blood vessels in many marine
mammals & birds allows for countercurrent exchange
- transfer heat betwe...
Canada goose

Bottlenose
dolphin

Blood flow
Artery

Vein

Vein
Artery

35ºC

33º

30º

27º

20º

18º

10º

9º

31
Some bony fishes & sharks also use countercurrent heat
exchange
Many endothermic insects also use this to help maintain
a ...
Cooling by Evaporative Heat Loss
• Many types of animals lose heat through evaporation
of water in sweat
• Panting increas...
Behavioral Responses
• Both endotherms & ectotherms use behavioral
responses to control body temperature
- some terrestria...
Adjusting Metabolic Heat Production
• Some animals can regulate body temperature by
adjusting their rate of metabolic heat...
O2 consumption (mL O2/hr) per kg

RESULTS
120

100
80
60
40
20
0
0

5

10

15

20

25

Contractions per minute

30

35
36
PREFLIGHT

PREFLIGHT
WARM-UP

Temperature (ºC)

40

FLIGHT
Thorax

35

30
Abdomen
25

0

2

Time from onset of warm-up (mi...
Acclimatization in Thermoregulation
• Birds & mammals can vary their insulation to
acclimatize to seasonal temperature cha...
39
Physiological Thermostats and Fever
• Thermoregulation is controlled by a region of the brain
called the hypothalamus
- tr...
Sweat glands secrete sweat,
which evaporates, cooling the
body.

Body temperature
decreases;
thermostat
shuts off cooling
...
Energy requirements are related to animal
size, activity, and environment
• Bioenergetics: the overall flow & transformati...
Energy Allocation and Use
• Animals harvest chemical energy from food

• Energy-containing molecules from food are usually...
External
environment

Organic molecules
in food

Animal
body

Digestion and
absorption

Heat
Energy lost
in feces

Nutrien...
Quantifying Energy Use
• Metabolic rate: the amount of energy an animal uses in a
unit of time
• Measured by determining t...
Minimum Metabolic Rate and
Thermoregulation
• Basal metabolic rate (BMR): the metabolic rate of an
endotherm at rest at a ...
103

BMR (L O2/hr) (log scale)

Elephant
Horse

102

Human
Sheep

10

Dog

Cat
1

10–1

Shrew

10–2
10–3

Rat
Ground squir...
Size and Metabolic Rate
• Metabolic rate per gram is inversely related to
body size among similar animals
- 1 g of mouse b...
BMR (L O2/hr) (per kg)

8
Shrew

7
6
5
4
3

Harvest mouse

2

Mouse

Sheep
Human
Elephant
Cat
Dog
Horse

Rat

1
Ground squ...
Activity and Metabolic Rate
• Activity greatly affects metabolic rate for
endotherms & ectotherms
• In general, the maximu...
Energy Budgets
• Different species use energy & materials in food in
different ways, depending on their environment
• Use ...
Annual energy expenditure (kcal/hr)

Endotherms
800,000
Basal
(standard)
metabolism

Reproduction

Ectotherm

Thermoregula...
Torpor and Energy Conservation
• Torpor: physiological state in which activity is low &
metabolism decreases
- enables ani...
Metabolic rate
(kcal per day)

200

Actual
metabolism

Additional metabolism that would be
necessary to stay active in win...
Estivation (summer torpor):
enables animals to
survive long periods of
high temperatures and
scarce water supplies
Daily t...
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  1. 1. Chapter 40: Basic Principles of Animal Form & Function Rob Swatski Associate Professor of Biology HACC – York Campus 1
  2. 2. Exchange with the Environment • An animal’s size & shape directly affect how it exchanges energy & materials with its environment • Exchange occurs as dissolved substances diffuse & are transported across the cells’ plasma membranes • A unicellular protist living in water has enough surface area of plasma membrane to service its entire volume of cytoplasm 2
  3. 3. Multicellular organisms with a sac body plan have body walls that are only 2 cells thick, which facilitates diffusion 3
  4. 4. More complex organisms have highly folded internal surfaces for exchanging materials External environment CO2 Food O2 Mouth Respiratory system 0.5 cm 50 µm Animal body Lung tissue Nutrients Heart Cells Circulatory system 10 µm Interstitial fluid Digestive system Excretory system Lining of small intestine Kidney tubules Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) 4
  5. 5. Epithelial Tissue Cuboidal epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Stratified squamous epithelium Simple squamous epithelium 5
  6. 6. Connective Tissue Loose connective tissue Chondrocytes Cartilage Elastic fiber Chondroitin sulfate Nuclei 100 µm 120 µm Collagenous fiber Fat droplets Adipose tissue Osteon 150 µm 30 µm Fibrous connective tissue White blood cells Blood 55 µm 700 µm Bone Central canal Plasma Red blood cells 6
  7. 7. Muscle Tissue Multiple nuclei Muscle fiber Sarcomere Skeletal muscle Nucleus 100 µm Intercalated disk 50 µm Cardiac muscle Nucleus Smooth muscle Muscle fibers 25 µm 7
  8. 8. Nervous Tissue 40 µm Dendrites Cell body Glial cells Axon Neuron Axons Blood vessel 15 µm 8
  9. 9. Coordination and Control • Depends on both the endocrine & nervous systems • The endocrine system: transmits chemical signals (hormones) to receptive cells throughout the body via blood - a hormone may affect 1 or more regions throughout the body • Hormones are relatively slow acting, but can have long-lasting effects 9
  10. 10. Stimulus Endocrine cell Hormone Signal travels everywhere via the bloodstream. (a) Signaling by hormones Blood vessel Response 10
  11. 11. • The nervous system: transmits information between specific locations • The information conveyed depends on a nerve signal’s (impulse) pathway, not the type of signal - impulse transmission is very fast - impulses can be received by neurons, muscle cells, & endocrine cells 11
  12. 12. Stimulus Neuron Axon Signal Signal travels along axon to a specific location. Signal Axons Response (b) Signaling by neurons 12
  13. 13. Feedback Control Loops • Animals manage their internal environment by regulating or conforming to the external environment • Regulators: use internal control mechanisms to moderate internal change in the face of external, environmental fluctuation • Conformers: allow internal conditions to vary with certain external changes 13
  14. 14. 40 Body temperature (°C) River otter (temperature regulator) 30 20 Largemouth bass (temperature conformer) 10 0 10 20 30 40 Ambient (environmental) temperature (ºC) 14
  15. 15. Homeostasis • Organisms use homeostasis to maintain a “steady state” (internal balance) regardless of external environment • In humans, body temperature, blood pH, & glucose concentration are each maintained at a constant level 15
  16. 16. Mechanisms of Homeostasis • Moderate changes in the internal environment • For a given variable, fluctuations above or below a set point act as a stimulus - stimuli are detected by a sensor & trigger a response - the response returns the variable back to the set point 16
  17. 17. Response: Heater turned off Room temperature decreases Stimulus: Control center (thermostat) reads too hot Set point: 20ºC Stimulus: Control center (thermostat) reads too cold Room temperature increases Response: Heater turned on 17
  18. 18. Homeostasis Response/effector Stimulus: Perturbation/stress Control center Sensor/receptor 18
  19. 19. Feedback Loops in Homeostasis • The dynamic equilibrium of most homeostasis is maintained by negative feedback loops - helps to return a variable to either a normal range or a set point - buildup of the end product shuts the system off • Positive feedback loops: do not usually contribute much to homeostasis 19
  20. 20. Alterations in Homeostasis • Set points & normal ranges can change with age or show cyclic variation • Homeostasis can adjust to changes in external environment, a process called acclimatization 20
  21. 21. Thermoregulation: process where animals maintain an internal temperature within a tolerable range • Ectothermic animals: gain heat from external sources - include most invertebrates, fishes, amphibians, & reptiles • Endothermic animals: generate heat by metabolism - birds & mammals 21
  22. 22. • Ectotherms generally tolerate more internal temperature variations • Endotherms are active at a greater range of external temperatures - more energetically expensive than ectothermy 22
  23. 23. Variation in Body Temperature • Poikilotherm: body temperature varies with its environment • Homeotherm: body temperature is relatively constant 23
  24. 24. Balancing Heat Loss and Gain Organisms exchange heat by 4 physical processes: Conduction Convection Radiation Evaporation 24
  25. 25. Radiation Convection Evaporation Conduction 25
  26. 26. Heat regulation in mammals often involves the integumentary system: skin, hair, & nails Hair Epidermis Sweat pore Muscle Dermis Nerve Sweat gland Hypodermis Adipose tissue Blood vessels Oil gland Hair follicle 26
  27. 27. 5 general adaptations help animals thermoregulate: – Insulation – Circulatory adaptations – Cooling by evaporative heat loss – Behavioral responses – Adjusting metabolic heat production 27
  28. 28. Insulation Major thermoregulatory adaptation in mammals & birds Skin, feathers, fur, & blubber reduce heat flow between an animal & its environment 28
  29. 29. Circulatory Adaptations • Regulation of blood flow near the body surface significantly affects thermoregulation • Many endotherms (& some ectotherms) can alter the amount of blood flowing between the body core & the skin - Vasodilation: blood flow in the skin increases, facilitating heat loss - Vasoconstriction: blood flow in the skin decreases, reducing heat loss 29
  30. 30. • The arrangement of blood vessels in many marine mammals & birds allows for countercurrent exchange - transfer heat between fluids flowing in opposite directions - important mechanism for minimizing heat loss 30
  31. 31. Canada goose Bottlenose dolphin Blood flow Artery Vein Vein Artery 35ºC 33º 30º 27º 20º 18º 10º 9º 31
  32. 32. Some bony fishes & sharks also use countercurrent heat exchange Many endothermic insects also use this to help maintain a high temperature in the thorax 32
  33. 33. Cooling by Evaporative Heat Loss • Many types of animals lose heat through evaporation of water in sweat • Panting increases the cooling effect in birds & many mammals • Sweating or bathing moistens the skin, helping to cool an animal down 33
  34. 34. Behavioral Responses • Both endotherms & ectotherms use behavioral responses to control body temperature - some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat 34
  35. 35. 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 (moving or shivering) 35
  36. 36. O2 consumption (mL O2/hr) per kg RESULTS 120 100 80 60 40 20 0 0 5 10 15 20 25 Contractions per minute 30 35 36
  37. 37. PREFLIGHT PREFLIGHT WARM-UP Temperature (ºC) 40 FLIGHT Thorax 35 30 Abdomen 25 0 2 Time from onset of warm-up (min) 4 37
  38. 38. Acclimatization in Thermoregulation • Birds & 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 - “plugs” gaps in existing crystals 38
  39. 39. 39
  40. 40. Physiological Thermostats and Fever • Thermoregulation is controlled by a region of the brain called the hypothalamus - triggers heat loss or heat-generating mechanisms • Fever is the result of a change to the set point for a biological thermostat 40
  41. 41. Sweat glands secrete sweat, which evaporates, cooling the body. Body temperature decreases; thermostat shuts off cooling mechanisms. Thermostat in hypothalamus activates cooling mechanisms. Blood vessels in skin dilate: capillaries fill; heat radiates from skin. Increased body temperature Homeostasis: Internal temperature of 36–38°C Body temperature Decreased body increases; thermostat temperature shuts off warming mechanisms. Blood vessels in skin constrict, reducing heat loss. Skeletal muscles contract; shivering generates heat. Thermostat in hypothalamus activates warming mechanisms. 41
  42. 42. Energy requirements are related to animal size, activity, and environment • Bioenergetics: the overall flow & transformation of energy in an animal • It determines how much food an animal needs & relates to an animal’s size, activity, & environment 42
  43. 43. 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 & repair, synthesis of storage material (fat), & production of gametes 43
  44. 44. External environment Organic molecules in food Animal body Digestion and absorption Heat Energy lost in feces Nutrient molecules in body cells Carbon skeletons Cellular respiration Energy lost in nitrogenous waste Heat ATP Biosynthesis Cellular work Heat Heat 44
  45. 45. Quantifying Energy Use • Metabolic rate: the amount of energy an animal uses in a unit of time • Measured by determining the amount of O2 consumed or CO2 produced 45
  46. 46. Minimum Metabolic Rate and Thermoregulation • Basal metabolic rate (BMR): the metabolic rate of an endotherm at rest at a “comfortable” temperature • Standard metabolic rate (SMR): the metabolic rate of an ectotherm at rest at a specific temperature • Both rates assume a nongrowing, fasting, & nonstressed animal • Ectotherms have much lower metabolic rates than endotherms of a comparable size 46
  47. 47. 103 BMR (L O2/hr) (log scale) Elephant Horse 102 Human Sheep 10 Dog Cat 1 10–1 Shrew 10–2 10–3 Rat Ground squirrel Mouse Harvest mouse 10–2 10–1 1 10 102 103 Body mass (kg) (log scale) (a) Relationship of BMR to body size 47
  48. 48. Size and Metabolic Rate • Metabolic rate per gram is inversely related to body size among similar animals - 1 g of mouse body mass requires 20-times more calories than 1 g of elephant body mass! • Smaller animals have a higher metabolic rate per gram - leads to a higher O2 delivery rate, breathing rate, heart rate, & greater (relative) blood volume, compared with a larger animal - must also eat much more food per unit of body mass 48
  49. 49. BMR (L O2/hr) (per kg) 8 Shrew 7 6 5 4 3 Harvest mouse 2 Mouse Sheep Human Elephant Cat Dog Horse Rat 1 Ground squirrel 0 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 49
  50. 50. Activity and Metabolic Rate • Activity greatly affects metabolic rate for endotherms & ectotherms • In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity 50
  51. 51. Energy Budgets • Different species use energy & materials in food in different ways, depending on their environment • Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, & reproduction 51
  52. 52. Annual energy expenditure (kcal/hr) Endotherms 800,000 Basal (standard) metabolism Reproduction Ectotherm Thermoregulation Growth Activity 340,000 4,000 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 8,000 4-kg female eastern indigo snake 52
  53. 53. Torpor and Energy Conservation • Torpor: physiological state in which activity is low & metabolism decreases - enables animals to save energy while avoiding difficult & dangerous conditions • Hibernation: long-term torpor that is an adaptation to winter cold & food scarcity 53
  54. 54. Metabolic rate (kcal per day) 200 Actual metabolism Additional metabolism that would be necessary to stay active in winter 100 0 Arousals 35 Body temperature 30 Temperature (°C) 25 20 15 10 5 0 –5 –10 –15 Outside temperature June August Burrow temperature October December February April 54
  55. 55. Estivation (summer torpor): enables animals to survive long periods of high temperatures and scarce water supplies Daily torpor: exhibited by many small birds & mammals - adapted to feeding patterns 55
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