Basic Principles of Animal Form and Function

1
Chapter 40

• Basic Principles of Animal Form and Function

2
Physical Laws and Animal Form

• The need to exchange materials with the
  environment place certain limits on the range of
  animal forms
• The ability to perform certain actions depends on
  an animals shape and size
• Evolutionary convergence reflects different
  species independent adaptation to a similar
  environmental challenge
• Fusiform shape in fast swimmers ?

Tuna
Shark
Penguin
Dolphin
Seal
3
Exchange with the Environment

• An animals 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

4
Unicellular organism

• A single-celled protist living in water has a
  sufficient surface area of plasma membrane to
  service its entire volume of cytoplasm

5
Multicellular Organismsimple

• 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
Hydra
(b) Two cell layers
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Multicellular Organism complex
External environment
Food
CO2
O2
Mouth
Animal body
Respiratory system
Blood
50 µm
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
Circulatory system
Nutrients
10 µm
Interstitial fluid
Digestive system
The lining of the small intestine, a diges- tive
organ, is elaborated with fingerlike projections
that expand the surface area for nutrient
absorption (cross-section, SEM).
Excretory system
Inside a kidney is a mass of microscopic tubules
that exhange chemicals with blood flowing
through a web of tiny vessels called capillaries
(SEM).
Anus
Unabsorbed matter (feces)
Metabolic waste products (urine)
Organisms with more complex body plans have
highly folded internal surfaces specialized for
exchanging materials
7
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

8
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
• nervous

9
Epithelial Tissue

• Epithelial tissue
• Covers the outside of the body and lines organs
  and cavities within the body
• Contains cells that are closely joined

10
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.

• Simple
• Stratified
• Columnar
• Cuboidal
• Squamous
• Pseudostratified

A simple columnar epithelium
A stratified columnar epithelium
A pseudostratified ciliated columnar epithelium
Stratified squamous epithelia
Cuboidal epithelia
Simple squamous epithelia
Basement membrane
40 µm
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Connective Tissue

• Connective tissue
• Functions mainly to bind and support other
  tissues
• Contains sparsely packed cells scattered
  throughout an extracellular matrix

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Connective tissue
CONNECTIVE TISSUE
100 µm
Chondrocytes
Collagenous fiber
Chondroitin sulfate
Elastic fiber
100 µm

• Loose
• Adipose
• Fibrous
• Cartilage
• Bone
• Blood

Cartilage
Loose connective tissue
Adipose tissue
Fibrous connective tissue
Fat droplets
Nuclei
150 µm
30 µm
Blood
Bone
Central canal
Red blood cells
White blood cell
Osteon
Plasma
700 µm
55 µm
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Muscle Tissue

• Muscle tissue
• Is composed of long cells called muscle fibers
  capable of contracting in response to nerve
  signals
• Three types
• Skeletal
• Cardiac
• Smooth

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Nervous Tissue

• Nervous tissue
• Senses stimuli and transmits signals throughout
  the animal
• Neurons
• Cell body
• Axon
• Dendrite

15
Muscle and Nervous tissue
MUSCLE TISSUE
100 µm
Skeletal muscle
Multiple nuclei
Muscle fiber
Sarcomere
Cardiac muscle
50 µm
Nucleus
Intercalated disk
Smooth muscle
Nucleus
Muscle fibers
25 µm
NERVOUS TISSUE
Process
Neurons
Cell body
Nucleus
50 µm
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Organs and Organ Systems

• In all but the simplest animals different tissues
  are organized into organs
• In some organs (like the stomach) tissues are
  arranged in layers
• At a higher level of organization, organ systems
  carry out the major body functions of most
  animals

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Organ Systems

• Organ systems in mammals

18
Bioenergetics

• Animals are Heterotrophs
• Animals consume food for the chemical energy
  stored in the molecules
• Energy is required for all life processes
• The flow of energy through an animal, its
  bioenergetics
• Ultimately limits the animals behavior, growth,
  and reproduction
• Determines how much food it needs

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Bioenergetics overview

• 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
Energy lost in feces
Nutrient molecules in body cells
Energy lost in urine
Cellular respiration
Carbon skeletons
Heat
ATP
Biosynthesis growth, storage, and reproduction
Cellular work
Heat
Heat
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Metabolic rate

• The amount of energy an animal uses in a unit of
  time

21
Measuring Metabolic rate

• One way is to determine the amount of oxygen
  consumed or carbon dioxide produced by an organism

22
Bioenergetic Strategies

• Birds and mammals are mainly endothermic
• Bodies are warmed mostly by heat generated by
  metabolism
• They typically have higher metabolic rates
• Capable of intense, long-duration activity
• Amphibians and reptiles other than birds are
  ectothermic
• They gain their heat mostly from external sources
• They have lower metabolic rates
• Incapable of intense activity over long periods

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Influences on Metabolic Rate
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Size and Metabolic Rate

• Metabolic rate per gram
• Is inversely related to body size among similar
  animals
• Each gram of mouse consumes 20 times the calories
  as each gram of elephant

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Activity and Metabolic Rate

• Basal metabolic rate (BMR)
• Is the metabolic rate of an endotherm at rest
• 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

26
Energy Budgets

• Different species of animals use the energy and
  materials in food in different ways, depending on
  their environment
• An animals use of energy is partitioned to BMR
  (or SMR), activity, homeostasis, growth, and
  reproduction

27
Regulating the Internal Environment

• Animals regulate their internal environment
  within relatively narrow limits
• The internal environment of vertebrates (where
  our cells live) is the interstitial fluid. It is
  very different from the external environment
• Homeostasis
• A dynamic balance between external changes and
  the animals internal control mechanisms that
  oppose the changes

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Regulating and Conforming

• Regulating and conforming are two extremes in how
  animals cope with environmental fluctuations
• 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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Mechanisms of Homeostasis

• Mechanisms of homeostasis moderate changes in the
  internal environment
• A homeostatic control system has three functional
  components
• receptor
• control center
• effector

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Feedback Circuits

• Negative feedback
• Where buildup of the end product of the system
  shuts the system off
• Positive feedback
• Involves a change in some variable that triggers
  mechanisms that amplify the change

31
Thermoregulation

• The process by which animals maintain an internal
  temperature within a tolerable range

32
Ectotherms and Endotherms

• Ectotherms
• Include most (but not all) invertebrates, fishes,
  amphibians, and non-bird reptiles
• Tolerate greater variation in internal
  temperature than endotherms
• Endotherms
• Include birds and mammals
• More energetically expensive than ectothermy

A few reptiles, fish, and insects are endotherms!
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Modes of Heat Exchange

• Radiation
• Evaporation
• Convection
• Conduction

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Balancing Heat Loss and Gain
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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

Cedar Waxwing
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Mammalian integument as insulation
Skin provides protection from mechanical injury,
infection and dessication Skin is important in
thermoregulation Adipose tissue of the hypodermis
supplies insulation of varying amount depending
upon the species
Hair
Epidermis
Sweat pore
Muscle
Dermis
Nerve
Sweat gland
Hypodermis
Adipose tissue
Blood vessels
Oil gland
Hair follicle
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Circulatory Adaptations

• Many endotherms and some ectotherms
• Can alter the amount of blood flowing between the
  body core and the skin
• 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

• Many marine mammals and birds have arrangements
  of blood vessels that are important for reducing
  heat loss

3
1
39
Countercurrent Heat Exchangers

• Some specialized ENDOTHERMIC bony fishes and
  sharks also possess countercurrent heat exchangers

(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 19C 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.
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Endothermic Insects

• Many endothermic insects have countercurrent heat
  exchangers that help maintain a high temperature
  in the thorax
• Strong flight muscles generate large amounts of
  heat when operating

Red areas indicate areas of high temp in this
winter-active moth
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Cooling by Evaporative Heat Loss

• Heat is lost through the evaporation of water in
  sweat
• Some animals pant to cool their bodies
• Bathing moistens the skin which helps to cool an
  animal down

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Behavioral Responses

• Posture Some terrestrial invertebrates have
  certain postures that enable them to minimize or
  maximize their absorption of heat from the sun
• Adjustment of metabolic heat production
• Many species of flying insects use shivering to
  warm up before taking flight

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Feedback Mechanisms in Thermoregulation

• Mammals regulate their body temperature by a
  complex negative feedback system that involves
  several organ systems
• In humans the hypothalamus contains a group of
  nerve cells that function as a thermostat

44
Adjustment to Changing Temperatures

• Acclimatization
• Many animals can adjust to a new range of
  environmental temperatures over a period of days
  or weeks
• May involve cellular adjustments (esp. in
  ectotherms)
• Change in membrane lipid composition
• Production of cryoprotectant (antifreezing)
  molecules
• Birds and mammals can make adjustments of
  insulation and metabolic heat production

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Torpor and Energy Conservation

• Torpor
• An adaptation that enables animals to save energy
  while avoiding difficult and dangerous conditions
• A physiological state in which activity is low
  and metabolism decreases
• 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
• Nocturnally feeding bats enter torpor while
  roosting during the daylight hours
• A hummingbird may enter turpor on a cold night
  and have its body temp lower by 25-30 degrees
  centigrade

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Hibernation is long-term torpor

• An adaptation to winter cold and food scarcity
  during which the animals body temperature
  declines

Periodic arousals may be needed to carry out some
body functions that require a high temperature
Additional metabolism that would be necessary to
stay active in winter
200
Actual metabolism
100
Metabolic rate (kcal per day)
0
Arousals
35
Body temperature
30
25
20
Temperature (C)
15
10
5
0
Outside temperature
Burrow temperature
-5
-10
-15
June
August
October
December
February
April
Beldings ground squirrel
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Bears
Grizzly
Hibernating black bears can go months without
eating, drinking, urinating, defecating or
exercising
The body temperature of a hibernating black bear
dips only to about 88 degrees. Much less of a
drop than that seen in many hibernating rodents
Kodiak Brown
Polar
Hibernation in black bears does not involve the
periodic arousals seen in many hibernating
rodents. Bears also slumber less deeply than the
rodents.