Download Lecture #11 * Animal Circulation and Gas Exchange Systems

Lecture #11 – Animal Circulation
and Gas Exchange Systems
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Key Concepts:
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Circulation and gas exchange – why?
Circulation – spanning diversity
Hearts – the evolution of double circulation
Blood circulation and capillary exchange
Blood structure and function
Gas exchange – spanning diversity
Breathing – spanning diversity
Respiratory pigments
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Animals use O2 and produce CO2
• All animals are aerobic
Lots of oxygen is required to support active
mobility
Some animals use lots of oxygen to maintain
body temperature
• All animals produce CO2 as a byproduct of
aerobic respiration
• Gasses must be exchanged
Oxygen must be acquired from the environment
Carbon dioxide must be released to the
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environment
Except……breaking news!
http://www.biomedcentral.com/1741-7007/8/30
Abstract – 6 April 2010
Background
Several unicellular organisms (prokaryotes and protozoa) can live under permanently anoxic conditions.
Although a few metazoans can survive temporarily in the absence of oxygen, it is believed that multicellular organisms cannot spend their entire life cycle without free oxygen. Deep seas include some of
the most extreme ecosystems on Earth, such as the deep hypersaline anoxic basins of the
Mediterranean Sea. These are permanently anoxic systems inhabited by a huge and partly unexplored
microbial biodiversity.
Results
During the last ten years three oceanographic expeditions were conducted to search for the presence of
living fauna in the sediments of the deep anoxic hypersaline L'Atalante basin (Mediterranean Sea). We
report here that the sediments of the L'Atalante basin are inhabited by three species of the animal phylum
Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp.) new to science. Using
radioactive tracers, biochemical analyses, quantitative X-ray microanalysis and infrared spectroscopy,
scanning and transmission electron microscopy observations on ultra-sections, we provide evidence that
these organisms are metabolically active and show specific adaptations to the extreme conditions of the
deep basin, such as the lack of mitochondria, and a large number of hydrogenosome-like organelles,
associated with endosymbiotic prokaryotes.
Conclusions
This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments.
Our findings allow us also to conclude that these metazoans live under anoxic conditions through an
obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes.
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The discovery of these life forms opens new perspectives for the study of metazoan life in habitats
lacking molecular oxygen.
Animals use O2 and produce CO2
• Circulation systems move gasses (and other
essential resources such as nutrients,
hormones, etc) throughout the animal’s
body
• Respiratory systems exchange gasses with
the environment
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Circulation systems have evolved
over time
• The most primitive animals exchange
gasses and circulate resources entirely by
diffusion
Process is slow and cannot support 3-D large
bodies
• Sponges, jellies and flatworms use diffusion
alone
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Critical Thinking
• Why isn’t diffusion adequate for exchange
in a 3D large animal???
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Critical Thinking
• Why isn’t diffusion adequate for exchange
in a 3D large animal???
• Surface area / volume ratio becomes too
small
• Remember, area is a square function;
volume is a cubic function
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Critical Thinking
• But…..plants rely on
diffusion for gas
exchange…..how do
they get so big???
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Critical Thinking
• But…..plants rely on
diffusion for gas
exchange…..how do
they get so big???
• Their living tissue is
close to the surface
and exposed to air –
either in the open
atmosphere or in the
soil atmosphere
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Circulation systems have evolved
over time
• The most primitive animals exchange
gasses and circulate resources entirely by
diffusion
Process is slow and cannot support 3-D large
bodies
Surface area / volume ratio becomes too small
• Sponges, jellies and flatworms use diffusion
alone
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Virtually every cell in a sponge is in direct
contact with the water – little circulation is
required
Diagram of sponge structure
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• Jellies and flatworms have thin bodies and
elaborately branched gastrovascular cavities
Again, all cells are very close to the external
environment
This facilitates diffusion
Some contractions help circulate (contractile
fibers in jellies, muscles in flatworms)
Diagram of jellyfish structure, and photos
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Circulation systems have evolved
over time
• Most invertebrates (esp. insects) have an
open circulatory system
 Metabolic energy is
used to pump
hemolymph through
blood vessels into the
body cavity
 Hemolymph is returned
to vessels via ostia –
pores that draw in the
fluid as the heart
relaxes
Diagram of open
circulatory system in a
grasshopper
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Circulation systems have evolved
over time
• Closed circulatory systems separate blood
from interstitial fluid
 Metabolic energy is
used to pump blood
through blood vessels
 Blood is contained
within the vessels
 Exchange occurs by
diffusion in capillary
beds
Diagram of a closed
circulatory system, plus
a diagram showing an
earthworm circulatory
system
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Open vs. Closed…both systems
are common
Open systems….
• Use less metabolic
energy to run
• Use less metabolic
energy to build
• Can function as a
hydrostatic skeleton
• Most invertebrates
(except earthworms
and larger mollusks)
have open systems
Closed systems….
• Maintain higher
pressure
• Are more effective at
transport
• Supply more oxygen
to support larger and
more active animals
• All vertebrates have
closed systems
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All vertebrates have a closed
circulatory system
• Chambered heart pumps blood
Atria receive blood
Ventricles pump blood
• Vessels contain the blood
Veins carry blood to atria
Arteries carry blood from ventricles
• Capillary beds facilitate exchange
Capillary beds separate arteries from veins
Highly branched and very tiny
We’ll go over these
Infiltrate all tissues in the body
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step by step
Chambered heart pumps blood
• Atria receive blood
• Ventricles pump
blood
Diagram of a chambered heart
• One-way valves
direct blood flow
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Critical Thinking
• Atria receive blood; ventricles pump
• Given that function, what structure would
you predict???
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Critical Thinking
• Atria receive blood; ventricles pump
• Given that function, what structure would
you predict???
• Atria are soft, flexible chambers
• Ventricles have much more muscular walls
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Chambered heart pumps blood
• Atria receive blood
Soft walled, flexible
• Ventricles pump
blood
Thick, muscular
walls
Diagram of a chambered heart
• One-way valves
direct blood flow
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Vessels contain the blood
• Arteries carry blood
from ventricles
Always under pressure
• Veins carry blood to
atria
One-way valves
prevent back flow
Body movements
increase circulation
Pressure is always low
Diagram showing
artery, vein and
capillary bed
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Note that blood vessel names reflect the
direction of flow, NOT the amount of
oxygen in the blood
• Arteries carry blood
AWAY from the heart
Arterial blood is always
under pressure
It is NOT always
oxygenated
Diagram of blood
circulation pattern
in humans
• Veins carry blood TO
the heart
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Capillary beds facilitate exchange
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Capillary beds separate arteries from veins
Highly branched and very tiny
Infiltrate all tissues in the body
More later
Diagram showing
artery, vein and
capillary bed
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All vertebrates have a closed
circulatory system – REVIEW
• Chambered heart pumps blood
Atria receive blood
Ventricles pump blood
• Vessels contain the blood
Veins carry blood to atria
Arteries carry blood from ventricles
• Capillary beds facilitate exchange
Capillary beds separate arteries from veins
Highly branched and very tiny
Infiltrate all tissues in the body
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Evolution of double circulation –
not all animals have a 4-chambered heart
Diagram showing progression from a 1chambered heart to a 4-chambered heart.
This diagram is used in the next 12 slides.
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Fishes have a 2-chambered heart
• One atrium, one ventricle
• A single pump of the heart
circulates blood through 2
capillary beds in a single circuit
Blood pressure drops as blood
enters the capillaries (increase in
cross-sectional area of vessels)
Blood flow to systemic capillaries
and back to the heart is very slow
Flow is increased by swimming
movements
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Two circuits increases the efficiency of
gas exchange = double circulation
• One circuit goes to exchange surface
• One circuit goes to body systems
• Both under high pressure – increases flow rate
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Amphibians have a 3-chambered heart
• Two atria, one ventricle
• Ventricle pumps to 2 circuits
One circuit goes to lungs and skin
to release CO2 and acquire O2
The other circulates through body
tissues
• Oxygen rich and oxygen poor
blood mix in the ventricle
A ridge helps to direct flow
• Second pump increases the
speed of O2 delivery to the body
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Most reptiles also have a 3-chambered
heart
• A partial septum further
separates the blood flow and
decreases mixing
Crocodilians have a complete
septum
• Point of interest: reptiles have
two arteries that lead to the
systemic circuits
Arterial valves help direct blood
flow away from pulmonary circuit
when animal is submerged
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Critical Thinking
• What is a disadvantage of a 3 chambered
heart???
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Critical Thinking
• What is a disadvantage of a 3 chambered
heart???
• Oxygen rich and oxygen poor blood mix in
the ventricle
• Less than maximum efficiency
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Mammals and birds have
4-chambered hearts
• Two atria and two ventricles
• Oxygen rich blood is completely
separated from oxygen poor blood
No mixing  much more efficient
gas transport
Efficient gas transport is essential
for both movement and support of
endothermy
Endotherms use 10-30x more
energy to maintain body
temperatures
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Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• What does this mean???
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Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT monophyletic
• Mammals and birds evolved from separate
reptilian ancestors
Phylogenetic tree showing
the diversification of
vertebrates
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Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• Four-chambered hearts evolved
independently
• What’s this called???
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Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• Four-chambered hearts evolved
independently
• Convergent evolution
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Review: evolution of double circulation
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