PNB 2250 Exam 3 Questions And Answers Latest Updates
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PNB 2250
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PNB 2250
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
so...
PNB 2250 Exam 3
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.
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.
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.
Examples of respiratory structures of terrestrial animals - bulk flow with tracheal system and
spiracles (insects), cutaneous (frog)
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 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 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
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
Lampreys have a single nostril that's not connected to the gut and have a row of gill pouches (7 per side)
that each have an external opening. Can be unidirectional when the fish is swimming and tidal when
attached to a surface (rock/host).
What is ram ventilation and which group of animals uses this? What is their anatomy like? -
Continuous swimming sharks use ram ventilation, which means that they move water over their
gills by swimming and "ramming" the water into their mouths and over their gills.
Sharks and rays have gill septa and unidirectional flow
Is ram ventilation attainable for sedentary species of sharks and rays? - For sharks, sedentary
skates, and rays that have to go at rest they use tidal ventilation through spiracles, because
unidirectional respiration requires continuous moving
How is the anatomy of the teleost gill suited for maximizing extraction of dissolved oxygen from the
water column? List two structural features of this organ that increase its surface area. - Gill arches
of teleosts are under the operculum cover and have no gill septa, as each column of free filament is
called the hemibranch. Spiracles are also covered over in teleosts. They use buccal-opercular pumps that
ensure unidirectional and continuous water flow across the gills.
By increasing the width and thickness of the gill filament, gas exchange is enhanced.
Describe the two phases of the buccal force pump in bony fishes by naming the head chambers and
kinds of pressure involved in each stage - Phase 1: suction pump → water enters the mouth via
negative pressure and the branchiostegal rays help seal the opercular chamber to help in this process
Phase 2: pressure pump → water is forced through the branchial basket using positive pressure created
by contracting the buccal chamber
How do the branchial arches and gill filaments of sharks differ structurally from those of teleosts? -
Sharks have a spiracle (which can be used to intake water, but does not itself have respiratory
epithelium), an attached hemibranch, and four holobranchs (=2 hemibranchs) on the gill arches, firmly
attached to septae. The frill-like flaps form the gill "slits' ' of the body wall.
Teleosts: have 4 holobranchs (no spiracle) covered by the operculum.
Hemibranchs are fused to a common septum in a shark, but are free 'drifting' in a teleost
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