USABO In-Depth - Circulatory and
Respiratory Systems
What is notable about diffusion time, and why is it so? - correct answer-Diffusion takes much
longer once you get past small distances (a few mm); because diffusion time is proportional
to square of distance
What are the 2 adaptations animals have evolved to allow for gas exchange? - correct
answer-1. A simple body plan that allows for many/all body cells to be in contact with env.
and exchange
2. Circulatory systems
What adaptation have certain cnidarians evolved that allows for gas exchange and
digestion? - correct answer-Gastrovascular cavity
In addition to cnidarians, which other major phylum above survives without a circulatory
system? - correct answer-Platyhelminthes (planarians and most other flatworms) - have a
gastrovascular cavity and a flat body for exchange
What are the advantages of open and closed circulatory systems? - correct answer-Open =
lower hydrostatic pressure, less energy
Closed = high blood pressure for effective delivery of O2 and nutrients for larger, more active
animals
Which mollusks have open and closed circulatory systems, and why? - correct
answer-Clams = open, Squid and Octopi = Closed; larger and more active = closed due to
better O2 and nutrient transmission
What are networks of capillaries called? - correct answer-Capillary beds
What is the only exception to the rule that all veins return blood to the heart from capillaries,
and why? - correct answer-The portal veins; they carry blood between pairs of capillary beds
What is an example of a portal vein? - correct answer-The hepatic portal vein; it carries
blood from digestive capillary beds to liver capillary beds
Which animals have single circulation? - correct answer-Sharks, rays, and bony fishes
How does single circulation work? - correct answer-1. Blood collects in atrium
2. Blood goes to ventricle; pumped into artery
3. Artery goes to gill capillary bed; blood oxygenated
4. Gill capillaries collect into major artery
5. Major artery divides into bodily capillary beds
6. Bodily capillary beds unite into vein that delivers blood to atrium
, What is notable about single circulation? - correct answer-Blood pressure drops substantially
after going past gill capillary bed; blood flow through rest of circulation is comparatively
sluggish
How can fishes accelerate single circulation? - correct answer-By moving = movement of
muscle stimulates blood vessels
What is the oxygen-getting circuit called in many amphibians, and why? - correct
answer-The pulmocutaneous circuit, because gas exchange surfaces are on the skin in
addition to the lungs
Why does double circulation provide more blood flow to organs such as the brain? - correct
answer-Blood repressurized after going through capillary beds of lungs or skin
What is a difference between the gas exchange circuit and the systemic circuit? - correct
answer-Systemic circuit blood pressure often much higher due to repressurization of blood
by heart (LV)
How can amphibians bypass lungs? - correct answer-1 whole Ventricle, 2 Atria
In situations where lungs would be useless (underwater), blood flow to lungs can be stopped
and blood can go to skin for gas exchange
How can turtles, snakes, and lizards hold their breaths? - correct answer-1 ventricle partially
divided, 2 atria
2 aortas present from both sides of ventricle (including right); pulmonary circuit can be
skipped
How can crocodilians hold their breaths? - correct answer-4 chambers, ventricle completely
divided
Arteries from both circuits same when leaving, so blood flow to lungs can stop when
underwater
How are birds and mammals different? - correct answer-Double circulation differs; Blood flow
to lungs cannot vary without affecting body; independent circuits and large hearts --> need to
deliver and transport 10 times as much bc endotherms
What arteries lead from the aorta? - correct answer-1. Coronary arteries - supply the heart
2. Head and arm arteries
3. Aorta goes down and supplies blood to arteries that go into the abdominal and leg regions
What do the atria serve as? - correct answer-Collection chambers for blood = they have
relatively thin walls
Where is the human heart located? - correct answer-Center of chest, behind sternum
How does blood enter the ventricles? - correct answer-When all 4 chambers are relaxed,
most blood enters ventricles through relaxed flow from atria; the remainder of blood enters
through atrial contraction at the beginning of heartbeat
Respiratory Systems
What is notable about diffusion time, and why is it so? - correct answer-Diffusion takes much
longer once you get past small distances (a few mm); because diffusion time is proportional
to square of distance
What are the 2 adaptations animals have evolved to allow for gas exchange? - correct
answer-1. A simple body plan that allows for many/all body cells to be in contact with env.
and exchange
2. Circulatory systems
What adaptation have certain cnidarians evolved that allows for gas exchange and
digestion? - correct answer-Gastrovascular cavity
In addition to cnidarians, which other major phylum above survives without a circulatory
system? - correct answer-Platyhelminthes (planarians and most other flatworms) - have a
gastrovascular cavity and a flat body for exchange
What are the advantages of open and closed circulatory systems? - correct answer-Open =
lower hydrostatic pressure, less energy
Closed = high blood pressure for effective delivery of O2 and nutrients for larger, more active
animals
Which mollusks have open and closed circulatory systems, and why? - correct
answer-Clams = open, Squid and Octopi = Closed; larger and more active = closed due to
better O2 and nutrient transmission
What are networks of capillaries called? - correct answer-Capillary beds
What is the only exception to the rule that all veins return blood to the heart from capillaries,
and why? - correct answer-The portal veins; they carry blood between pairs of capillary beds
What is an example of a portal vein? - correct answer-The hepatic portal vein; it carries
blood from digestive capillary beds to liver capillary beds
Which animals have single circulation? - correct answer-Sharks, rays, and bony fishes
How does single circulation work? - correct answer-1. Blood collects in atrium
2. Blood goes to ventricle; pumped into artery
3. Artery goes to gill capillary bed; blood oxygenated
4. Gill capillaries collect into major artery
5. Major artery divides into bodily capillary beds
6. Bodily capillary beds unite into vein that delivers blood to atrium
, What is notable about single circulation? - correct answer-Blood pressure drops substantially
after going past gill capillary bed; blood flow through rest of circulation is comparatively
sluggish
How can fishes accelerate single circulation? - correct answer-By moving = movement of
muscle stimulates blood vessels
What is the oxygen-getting circuit called in many amphibians, and why? - correct
answer-The pulmocutaneous circuit, because gas exchange surfaces are on the skin in
addition to the lungs
Why does double circulation provide more blood flow to organs such as the brain? - correct
answer-Blood repressurized after going through capillary beds of lungs or skin
What is a difference between the gas exchange circuit and the systemic circuit? - correct
answer-Systemic circuit blood pressure often much higher due to repressurization of blood
by heart (LV)
How can amphibians bypass lungs? - correct answer-1 whole Ventricle, 2 Atria
In situations where lungs would be useless (underwater), blood flow to lungs can be stopped
and blood can go to skin for gas exchange
How can turtles, snakes, and lizards hold their breaths? - correct answer-1 ventricle partially
divided, 2 atria
2 aortas present from both sides of ventricle (including right); pulmonary circuit can be
skipped
How can crocodilians hold their breaths? - correct answer-4 chambers, ventricle completely
divided
Arteries from both circuits same when leaving, so blood flow to lungs can stop when
underwater
How are birds and mammals different? - correct answer-Double circulation differs; Blood flow
to lungs cannot vary without affecting body; independent circuits and large hearts --> need to
deliver and transport 10 times as much bc endotherms
What arteries lead from the aorta? - correct answer-1. Coronary arteries - supply the heart
2. Head and arm arteries
3. Aorta goes down and supplies blood to arteries that go into the abdominal and leg regions
What do the atria serve as? - correct answer-Collection chambers for blood = they have
relatively thin walls
Where is the human heart located? - correct answer-Center of chest, behind sternum
How does blood enter the ventricles? - correct answer-When all 4 chambers are relaxed,
most blood enters ventricles through relaxed flow from atria; the remainder of blood enters
through atrial contraction at the beginning of heartbeat
