USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
,USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
,USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
, USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
,USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
,USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
, USABO In-Depth - Circulatory and
Respiratory Systems Exam Questions
& Answers (Grade A+)
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
