PNB 2250 Exam 3 Questions and
Answers 100% Pass
Examples of respiratory structures of terrestrial animals - ✔✔bulk flow with tracheal
system and spiracles (insects), cutaneous (frog)
Examples of respiratory structures of aquatic animals - ✔✔bulk flow (sponges,
cnidarians), gills, water vascular system, arborescent respiratory trees (sea cucumber),
cutaneous (leech)
Do all aquatic animals necessarily exchange gasses in water? - ✔✔No, some aquatic
animals could exchange gasses above water using lungs, like aquatic mammals, or
cutaneous respiration, like frogs, which takes advantage of moist skin rather than being
in the water
Relationship between a gas's volume and its pressure - ✔✔Volume and pressure are
inversely related because in a higher volume gas has more room to move, which means
it has a lower pressure.
What is a gas's partial pressure? - ✔✔A partial pressure is the independent gas's
exertion of pressure on the walls of a container via molecular collisions.
Katelyn Whitman, All Rights Reserved © 2025 1
,How does O2 and CO2 differ in their solubility & concentration in water versus in air? -
✔✔Solubility of oxygen is lower in water than air, while CO2 reacts with water to form
bicarbonate and carbonic acid. Oxygen is in higher concentration than CO2 in both air
and water. Warmer water and salt water holds less oxygen
What happens to air pressure as elevation increases? What happens to water pressure
as depth increases? - ✔✔As elevation increases, air pressure decreases.
As depth increases in water, pressure increases.
How might water's density and viscosity affect the energy required for ventilation by
aquatic animals compared to that in air-breathers? How does this impact locomotion? -
✔✔Water has a high viscosity and density, which means that it is thicker and heavier.
This means that water holds less oxygen than the air does. This means that locomotion
is also hard for aquatic mammals.
Name an animal that has neither a circulatory system nor a respiratory system and
relies solely on cutaneous diffusion for gas exchange. How is this adequate for its
survival? - ✔✔Small and thin animals, like flatworms and horsehair worm parasites,
have no respiratory or circulatory systems and solely rely on cutaneous/cuticle
diffusion through water or air.
Katelyn Whitman, All Rights Reserved © 2025 2
,Name one aquatic and one terrestrial animal that respires cutaneously, but moves the
diffused gasses through a circulatory system - ✔✔Long animals use cutaneous
respiration and moves the gas to the circulatory system
Aquatic cutaneous: leech
Terrestrial cutaneous: frog
Name one aquatic and one terrestrial animal that has the opposite physiological setup:
one that lacks a circulatory system (at least one used primarily for gas exchange) and
respires using bulk flow of the medium (water or air) - ✔✔Bulk flow animals have no
circulatory system
Aquatic: sponge, cnidarian
Terrestrial: insect (tracheal system and spiracles)
Name an aquatic and terrestrial animal that utilizes a bulk flow step in both their
respiratory and circulatory systems and identify the two sites of gas diffusion during
the transport of O2 and CO2 through the body. - ✔✔Animals that utilize bulk flow in
their respiratory and circulatory systems
Aquatic: mollusks, crustaceans
Terrestrial: vertebrates
Katelyn Whitman, All Rights Reserved © 2025 3
, It diffuses into respiratory vasculature of the alveoli and respiring cells through the
capillaries, where it enters mitochondria for aerobic respiration.
What are the gills of a mollusk called (which also double as a ciliated, filter-feeding
structure in bivalves)? - ✔✔Ctenidia are large leaf-like organs that are used partly for
respiration and partly for filtering food from the water in mollusks
How do cephalopods actively move water across their gills? - ✔✔Cephalopods have
paired gills and muscles that force water through a mantle cavity
How do crustaceans, such as crabs, shrimp, and crayfish, breathe? - ✔✔Crustaceans
have gills that are highly modified and located at the base of each leg under the
carapace. The water flow is unidirectional, entering the ventral side and exiting the
bailer (anterior) near the mouth
Describe at least two ways that different echinoderms can respire in water without gills.
- ✔✔Sea Stars use both external respiratory papulae and a water vascular system.
Sea cucumbers have arborescent respiratory trees stemming from their cloaca
(breathing out of anus)
How do hagfish differ from lampreys? (hint: nostril) - ✔✔Hagfish have a single nostril
connected to the esophagus and ventilate using a muscular velum - moves to propel
water unidirectionally through the mouth, down the pharynx, and into the bilateral
atria that exits the body through the atriopore opening
Katelyn Whitman, All Rights Reserved © 2025 4
Answers 100% Pass
Examples of respiratory structures of terrestrial animals - ✔✔bulk flow with tracheal
system and spiracles (insects), cutaneous (frog)
Examples of respiratory structures of aquatic animals - ✔✔bulk flow (sponges,
cnidarians), gills, water vascular system, arborescent respiratory trees (sea cucumber),
cutaneous (leech)
Do all aquatic animals necessarily exchange gasses in water? - ✔✔No, some aquatic
animals could exchange gasses above water using lungs, like aquatic mammals, or
cutaneous respiration, like frogs, which takes advantage of moist skin rather than being
in the water
Relationship between a gas's volume and its pressure - ✔✔Volume and pressure are
inversely related because in a higher volume gas has more room to move, which means
it has a lower pressure.
What is a gas's partial pressure? - ✔✔A partial pressure is the independent gas's
exertion of pressure on the walls of a container via molecular collisions.
Katelyn Whitman, All Rights Reserved © 2025 1
,How does O2 and CO2 differ in their solubility & concentration in water versus in air? -
✔✔Solubility of oxygen is lower in water than air, while CO2 reacts with water to form
bicarbonate and carbonic acid. Oxygen is in higher concentration than CO2 in both air
and water. Warmer water and salt water holds less oxygen
What happens to air pressure as elevation increases? What happens to water pressure
as depth increases? - ✔✔As elevation increases, air pressure decreases.
As depth increases in water, pressure increases.
How might water's density and viscosity affect the energy required for ventilation by
aquatic animals compared to that in air-breathers? How does this impact locomotion? -
✔✔Water has a high viscosity and density, which means that it is thicker and heavier.
This means that water holds less oxygen than the air does. This means that locomotion
is also hard for aquatic mammals.
Name an animal that has neither a circulatory system nor a respiratory system and
relies solely on cutaneous diffusion for gas exchange. How is this adequate for its
survival? - ✔✔Small and thin animals, like flatworms and horsehair worm parasites,
have no respiratory or circulatory systems and solely rely on cutaneous/cuticle
diffusion through water or air.
Katelyn Whitman, All Rights Reserved © 2025 2
,Name one aquatic and one terrestrial animal that respires cutaneously, but moves the
diffused gasses through a circulatory system - ✔✔Long animals use cutaneous
respiration and moves the gas to the circulatory system
Aquatic cutaneous: leech
Terrestrial cutaneous: frog
Name one aquatic and one terrestrial animal that has the opposite physiological setup:
one that lacks a circulatory system (at least one used primarily for gas exchange) and
respires using bulk flow of the medium (water or air) - ✔✔Bulk flow animals have no
circulatory system
Aquatic: sponge, cnidarian
Terrestrial: insect (tracheal system and spiracles)
Name an aquatic and terrestrial animal that utilizes a bulk flow step in both their
respiratory and circulatory systems and identify the two sites of gas diffusion during
the transport of O2 and CO2 through the body. - ✔✔Animals that utilize bulk flow in
their respiratory and circulatory systems
Aquatic: mollusks, crustaceans
Terrestrial: vertebrates
Katelyn Whitman, All Rights Reserved © 2025 3
, It diffuses into respiratory vasculature of the alveoli and respiring cells through the
capillaries, where it enters mitochondria for aerobic respiration.
What are the gills of a mollusk called (which also double as a ciliated, filter-feeding
structure in bivalves)? - ✔✔Ctenidia are large leaf-like organs that are used partly for
respiration and partly for filtering food from the water in mollusks
How do cephalopods actively move water across their gills? - ✔✔Cephalopods have
paired gills and muscles that force water through a mantle cavity
How do crustaceans, such as crabs, shrimp, and crayfish, breathe? - ✔✔Crustaceans
have gills that are highly modified and located at the base of each leg under the
carapace. The water flow is unidirectional, entering the ventral side and exiting the
bailer (anterior) near the mouth
Describe at least two ways that different echinoderms can respire in water without gills.
- ✔✔Sea Stars use both external respiratory papulae and a water vascular system.
Sea cucumbers have arborescent respiratory trees stemming from their cloaca
(breathing out of anus)
How do hagfish differ from lampreys? (hint: nostril) - ✔✔Hagfish have a single nostril
connected to the esophagus and ventilate using a muscular velum - moves to propel
water unidirectionally through the mouth, down the pharynx, and into the bilateral
atria that exits the body through the atriopore opening
Katelyn Whitman, All Rights Reserved © 2025 4
