Gas Exchange and Respiration

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Gas Exchange and Respiration I. Selective
Forces -- Eukaryotic organisms must exchange
gases with environment -- All gas exchange must
occur via diffusion across moist membrane
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Gas Exchange and Respiration I. Selective
Forces A. Problems associated with
diffusion 1. must expose moist body surface to
environment 2. limitations to diffusion
a. surface area as surface area amount
of gas diffusing -- respiratory membranes
have enormous surface areas
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Gas Exchange and Respiration I. Selective
Forces A. Problems associated with
diffusion 1. must expose moist body surface to
environment 2. limitations to diffusion
b. partial pressure of gas -- PP gas
solution -- as difference in PP of gas
across membrane amount of gas
diffusing , because of greater diffusion
gradient -- animals must keep PP of gases ?
across respiratory membrane
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Gas Exchange and Respiration I. Selective
Forces A. Problems associated with
diffusion 1. must expose moist body surface to
environment 2. limitations to diffusion
c. surface/volume ratio -- body volume
increases faster than surface area --
diffusion alone is sufficient to supply all gas
needs without modifications only if
diameter of body is lt 1 mm.
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 1. countercurrent exchange
systems -- often found in aquatic
respiratory structures -- blood flows
through gills in opposite direction that water
flows over gills -- prevents equilibration
of PP O2 across gill membrane a.
Concurrent exchange -- PP O2 reaches
equilibrium -- can extract only 50 of
available O2 from water
Blood flow
5 20 40 50 50 50
100 80 60 50 50 50
Water flow
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 1. countercurrent exchange
systems -- often found in aquatic
respiratory structures -- blood flows
through gills in opposite direction that water
flows over gills -- prevents equilibration
of PP O2 across gill membrane a.
Countercurrent exchange -- PP O2 never reaches
equilibrium across respiratory membrane --
continue to extract O2 throughout length of flow
Blood flow
5 20 30 50 70 90
10 30 40 60 80 100
Water flow
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
-- increase O2 carrying capacity of a fluid
-- affinity for O2 must change must bind
easily with O2 at respiratory device,
but easily release O2 in tissues a.
types of respiratory pigments 1)
hemocyanin -- copper based -- found in
many mollusks and arthropods -- bluish in
color when bound with O2
octopus
arthropod
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
a. types of respiratory pigments 2)
hemoglobin -- iron based -- found in
vertebrates, annelids, some mollusks, some insects
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
a. types of respiratory pigments 3)
myoglobin -- iron based -- in cardiac,
slow oxidative, and fast oxidative muscle fibers
of vertebrates -- has slightly
greater affinity for O2 than hemoglobin helps to
pull O2 from blood into muscle fiber
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
b. Factors affecting hemoglobins affinity for
O2 1) PP O2 as PP O2
affinity as PP O2
affinity -- hemoglobin binds with O2
where levels are high (gills, lungs) --
releases O2 where levels are low (tissues)
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
b. Factors affecting hemoglobins affinity for
O2 2) cooperativity --
binding of one O2 enhances binding of others
release of one O2 enhances release of
others
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Gas Exchange and Respiration I. Selective
Forces B. General mechanisms for increasing
oxygen uptake 2. respiratory pigments
b. Factors affecting hemoglobins affinity for
O2 3) pH ( -logH) --
measure of the acidity (H) of a solution --
ranges from 0-14 -- as pH decreases (becomes
more acidic), affinity for O2 decreases -- pH
of blood regulated by CO2 -- CO2 diffuses into
red blood cells CO2 H2O H2CO3
H HCO3- -- H combines with hemoglobin,
releasing O2 -- thus, as CO2 increases in
tissues, pH decreases, and hemoglobin
releases O2 easier
carbonic anhydrase
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• Gas Exchange and Respiration
• II. Respiration in aquatic environments
• A. The environment
• -- compared to air, little O2 in water (only 5
  that of air)
• -- water is viscous requires energy to
  ventilate gills (fish use 20 of daily energy for
  ventilation mammals use 1-2)
• -- O2 in water is not constant varies with
  
• Salinity as salinity increases, O2 decreases
• Temperature as temp. increases, O2 decreases

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Gas Exchange and Respiration II. Respiration in
aquatic environments A. The environment B.
Respiratory mechanisms 1. body surface
(no respiratory system)
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Gas Exchange Across Body Surface
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Gas Exchange Across Body Surface
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Gas Exchange and Respiration II. Respiration in
aquatic environments B. Respiratory
mechanisms 2. Mollusca gills contained
within mantle cavity
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Gas Exchange and Respiration II. Respiration in
aquatic environments B. Respiratory
mechanisms 2. Mollusca mantle cavity of
gastropods
siphon
Mantle cavity
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Gas Exchange and Respiration II. Respiration in
aquatic environments B. Respiratory
mechanisms 3. crustaceans gills and
gill bailers
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Gas Exchange and Respiration II. Respiration in
aquatic environments B. Respiratory
mechanisms 4. Echinoderms dermal
branchia
Dermal branchia


Dermal branchia
ossicle
enterocoelom
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Gas Exchange and Respiration II. Respiration in
aquatic environments B. Respiratory
mechanisms 5. Fish gills --
relationship between swimming speed and gill
surface area -- ventilate by using mouth
to actively pump water over gills or swim
with mouth open
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(p. 517)
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Figure 24.29b
(p. 517)
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Figure 24.29c
(p. 517)
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Gas Exchange and Respiration III. Respiration in
terrestrial environments A. The
environment -- air is 21 oxygen -- primary
limiting factor is water loss
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 1. body surface (no respiratory
system) limited to areas with 100
humidity
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 2. modified gills of isopods (pill
bugs, rolly pollies only truly terrestrial
crustacean)
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 2. modified gill chamber of land
crabs
Land crab
Ghost crab
Coconut crab
Fiddler crab
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 3. trachea insects and some
arachnids a. structure
air sac
trachea
tracheal trunk
spiracle
tracheole end cells tracheoles
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 3. trachea insects and some
arachnids b. function --
air drawn through trachea -- O2
dissolves in fluid in tracheal end cell
into tracheoles and surrounding tissues
c. ventilation -- telescoping
of abdomen -- body movement
air sac
trachea
tracheal trunk
spiracle
tracheal end cell tracheoles
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs a. diffusion
lungs no active ventilation ex
Pulmonate snails (highly vascularized mantle
cavity)
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs a. diffusion
lungs no active ventilation ex
Pulmonate snails (highly vascularized mantle
cavity)
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs a. diffusion
lungs no active ventilation ex book
lungs of arachnids
hemocoel with hemolymph
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs b. ventilation
lungs mammals 1) structure
pharynx
larynx
trachea
bronchus
bronchioles
alveoli
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• Gas Exchange and Respiration
• III. Respiration in terrestrial environments
• B. Respiratory mechanisms
• 4. lungs
• b. ventilation lungs mammals
• 2) ventilation
• -- use a tidal flow of air expansive lungs
• Inhalation
• -- diaphragm lowers
• -- external intercostal muscles pull ribs
  outwards and up
• -- expands volume of thoracic cavity air sucked
  in
• -- pulmonary surfactants
• Exhalation
• -- diaphragm rises abdominal muscles contract
• -- internal intercostal muscles pull ribs
  inwards and down
• -- decreases volume of thoracic cavity
  and air is expelled

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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs b. ventilation
lungs mammals 3) regulation of
breathing -- controlled by medulla
oblongata -- chemoreceptors respond to
decreasing pH of cerebrospinal fluid CO2
H2O H2CO3 H HCO3- --
stimulate both rate and depth of breathing
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs b. ventilation
lungs birds -- respiratory system
of birds much larger than that of mammals 20
of body volume -- extracts 31
of O2 mammalian system extracts 24
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs b. ventilation
lungs birds 1) structure
trachea
syrinx
bronchus
anterior air sacs
parabronchi
lung
posterior air sacs
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Gas Exchange and Respiration III. Respiration in
terrestrial environments B. Respiratory
mechanisms 4. lungs b. ventilation
lungs birds 2) air flow (p.
580) -- lungs non-expansive -- maintain
one-way flow of air (not tidal flow) --
continuous flow of air from bottom of lungs to
top -- requires two complete inhalation/exhala
tion cycles to move one breath through system
trachea
syrinx
bronchus
anterior air sacs
parabronchi
lung
posterior air sacs
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• inhalation 1
• -- inhaled air (breath 1) bypasses lungs
  moves into posterior
• air sacs some into base of parabronchi
• -- air in lungs (previous breath) moves
  upward
• through parabronchi and into anterior
  air sacs
• exhalation 1
• -- air (breath 1) moves from posterior air
  sacs into parabronchi
• -- air in anterior air sacs (previous breath)
  exits body
• inhalation 2
• -- inhaled air (breath 2) bypasses
• lungs and moves into post. air
• sacs and base of parabronchi
• -- breath 1 moves upward into ant.
• air sacs
• exhalation 2
• -- breath 2 move through parabronchi

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Figure 27.CO