Download 1. Exoskeletons and endoskeletons differ in that

1. Exoskeletons and endoskeletons differ in that—
a. an exoskeleton is rigid, and an endoskeleton is flexible
b. endoskeletons are found only in vertebrates
c. exoskeletons are composed of calcium, and endoskeletons are built from
chitin
d. exoskeletons are external to the soft tissues, and endoskeletons are internal
The correct answer is d—
A. Answer a is incorrect. Both exoskeletons and endoskeletons provide rigid support.
The correct answer is d—
B. Answer b is incorrect. Endoskeletons are also found in echinoderms.
The correct answer is d—
C. Answer c is incorrect. Exoskeletons contain chitin, and endoskeletons use various
forms of calcium.
The correct answer is d—exoskeletons are external to the soft tissues, and endoskeletons
are internal
D. Answer d is correct.
2. Worms and marine invertebrates use a hydrostatic skeleton to generate
movement. How do they do this?
a. Their bones are filled with water, which provides the weight of the
skeleton.
b. The change in body structure is caused by contraction of muscles
compressing the watery body fluid.
c. The muscles contain water vacuoles, which, when filled, provide a rigid
internal structure.
d. The term hydrostatic simply refers to moist environment. They generate
movement just as arthropods do.
The correct answer is b—
A. Answer a is incorrect. A hydrostatic skeleton is not composed of water-filled
bones.
The correct answer is b—The change in body structure is caused by contraction of
muscles compressing the watery body fluid.
B. Answer b is correct. Muscle contraction squeezes the body fluid (the “hydro”) and
forces it to move in a given direction. This in turn extends the body, causing
movement.
The correct answer is b—
C. Answer c is incorrect. The muscles do not contain water-filled vacuoles.
The correct answer is b—
D. Answer d is incorrect. Worms and marine invertebrates do not use the same
mechanisms as arthropods (who have an exoskeleton).
3. You take X-rays of two individuals. Ray has been a weightlifter and body builder
for 30 years. Ben has led a mostly sedentary life. What differences would you
expect in their X-ray films?
a. No difference, they would both have thicker bones than a younger person
due to natural thickening with age.
b. No difference, lifestyle does not affect bone density
c. Ray would have thicker bones due to reshaping as a result of physical
stress.
d. Ben would have thicker bones because bone accumulates like fat tissue
from a sedentary lifestyle.
The correct answer is c—
A. Answer a is incorrect. The skeleton is remodeled according to mechanical stress
and nutrition, not age.
The correct answer is c—
B. Answer b is incorrect. Lifestyle (exercise and diet habits) does cause changes in
bone thickness.
The correct answer is c—Ray would have thicker bones due to reshaping as a result of
physical stress.
C. Answer c is correct.
The correct answer is c—
D. Answer d is incorrect. Inactivity or lack of physical stress, would tend to make
bone smaller, not larger (think of what happens to a limb that is immobilized for
months or years).
4. Bone develops by one of two mechanisms depending on the underlying scaffold.
Which pairing correctly describes these mechanisms?
a. Intramembranous and extramembranous
b. Endochondral and exochondral
c. Extramembranous and exochondral
d. Endochondral and intramembranous
The correct answer is d—
A. Answer a is incorrect. Extramembranous is not a term used to describe methods
of skeletal development.
The correct answer is d—
B. Answer b is incorrect. Exochondral (“outside of cartilage”) is not a term used to
describe methods of skeletal development.
The correct answer is d—
C. Answer c is incorrect. Exochondral (“outside of cartilage”) and extramembranous
(“outside of membrane”) are not terms used to describe methods of skeletal
development.
The correct answer is d—Endochondral and intramembranous
D. Answer e is correct.
5. Which of the following statements best describes the sliding filament mechanism
of muscle contraction?
a. Actin and myosin filaments do not shorten, but rather, slide past each
other.
b. Actin and myosin filaments shorten and slide past each other.
c. As they slide past each other, actin filaments shorten, but myosin
filaments do not shorten.
d. As they slide past each other, myosin filaments shorten, but actin
filaments do not shorten.
The correct answer is a—Actin and myosin filaments do not shorten, but rather, slide past
each other.
A. Answer a is correct. Evidence indicates that the filaments do not shorten in and of
themselves but instead slide past each other.
The correct answer is a—
B. Answer b is incorrect. Actin and myosin do not shorten during contraction
although the overall muscle length does.
The correct answer is a—
C. Answer c is incorrect. Neither actin nor myosin shortens during contraction,
although the overall muscle length does.
The correct answer is a—
D. Answer d is incorrect. Neither actin nor myosin shortens during contraction,
although the overall muscle length does.
6. You have identified a calcium storage disease in rats. How would this inability to
store Ca2+ affect muscle contraction?
a. Ca2+ would be unable to bind to tropomyosin, which enables troponin to
move and reveal binding sites for cross-bridges.
b. Ca2+ would be unable to bind to troponin, which enables tropomyosin to
move and reveal binding sites for cross-bridges.
c. Ca2+ would be unable to bind to tropomyosin, which enables troponin to
release ATP.
d. Ca2+ would be unable to bind to troponin, which enables tropomyosin to
release ATP.
The correct answer is b—
A. Answer a is incorrect. Ca2+ binds to troponin, which sits atop tropomyosin not the
other way around.
The correct answer is b—CA2+ would be unable to bind to troponin, which enables
tropomyosin to move and reveal binding sites for cross-bridges.
B. Answer b is correct.
The correct answer is b—
C. Answer c is incorrect. Ca2+ binds to troponin not tropomyosin. Also, troponin
does not bind ATP.
The correct answer is b—
D. Answer d is incorrect. Tropomyosin neither binds nor releases ATP.
7. Motor neurons stimulate muscle contraction via the release of—
a. Ca2+
b. ATP
c. acetylcholine
d. hormones
The correct answer is c—
A. Answer a is incorrect. Although increase in intracellular Ca2+ causes muscle
contraction, it is acetylcholine that is released by the motor neuron.
The correct answer is c—
B. Answer b is incorrect. ATP is not released by the motor neuron.
The correct answer is c—acetylcholine
C. Answer c is correct.
The correct answer is c—
D. Answer d is incorrect. Motor neurons release acetylcholine, not hormones (which
are released by glands).
8. Which of the following statements about muscle metabolism is false?
a. Skeletal muscles at rest obtain most of their energy from muscle glycogen
and blood glucose.
b. ATP can be quickly obtained by combining ADP with phosphate derived
from creatine phosphate.
c. Exercise intensity is related to the maximum rate of oxygen consumption.
d. ATP is required for the pumping of the Ca2+ back into the sarcoplasmic
reticulum.
The correct answer is a—Skeletal muscles at rest obtain most of their energy from muscle
glycogen and blood glucose.
A. Answer a is correct because it is false. Muscles at rest obtain most of their ATP
by metabolizing fatty acids.
The correct answer is a—
B. Answer b is incorrect because it is true. ATP can be obtained by phosphorylating
ADP using phosphate from creatine phosphate.
The correct answer is a—
C. Answer c is incorrect because it is true. Exercise intensity is related to oxygen
consumption.
The correct answer is a—
D. Answer d is incorrect because it is true. Ca2+ is actively pumped back into the
sarcoplasmic reticulum at the end of a twitch cycle. This requires ATP.
9. If you wanted to study the use of ATP during a single contraction cycle within a
muscle cell, which of the following processes would you use?
a. Summation
b. Twitch
c. Treppe
d. Tetanus
The correct answer is b—
A. Answer a is incorrect. Summation refers to multiple twitch events.
The correct answer is b—Twitch
B. Answer b is correct.
The correct answer is b—
C. Answer c is incorrect. Treppe is not a single contraction, it is a gradual buildup of
contractions.
The correct answer is b—
D. Answer d is incorrect. Tetanus refers to the maximal contraction of a muscle.
10. Place the following events in the correct order—
1. Sarcoplasmic reticulum releases Ca2+
2. Myosin binds to actin
3. Action potential arrives from neuron
4. Ca2+ binds to troponin
a. 1, 2, 3, 4
b. 3, 1, 2, 4
c. 2, 4, 3, 1
d. 3, 1, 4, 2
The correct answer is d—
A. Answer a is incorrect. The action potential must occur before the other events.
The correct answer is d—
B. Answer b is incorrect. Ca2+ must bind to troponin before myosin binds to actin.
The correct answer is d—
C. Answer c is incorrect. Ca2+ must bind to troponin before myosin binds to actin.
The correct answer is d—3, 1, 4, 2
D. Answer d is correct.
11. How do the muscles move hand through space?
a. By contraction
b. By attaching to two bones across a joint
c. By lengthening
d. Both a and b are correct
The correct answer is d—
A. Answer a is incorrect. It is not the only correct answer.
The correct answer is d—
B. Answer b is incorrect. It is not the only correct answer.
The correct answer is d—
C. Answer c is incorrect. Lengthening does not provide the force required to move
the body through space.
The correct answer is d—Both a and b are correct
D. Answer d is correct. It includes both of the correct choices.
12. Differences in which of the following permit animal flight?
a. Gravity
b. Humidity
c. Pressure
d. Temperature
The correct answer is c—
A. Answer a is incorrect. Gravity is not variable for flying animals.
The correct answer is c—
B. Answer b is incorrect. Differences in humidity do not generate the uplift
necessary for flight.
The correct answer is c—Pressure
C. Answer c is correct.
The correct answer is c—
D. Answer d is incorrect. Temperature differences above and below the wing are not
sufficient to allow flight.
12. How can osteocytes remain alive within bone?
a. Bones are composed of only dead or dormant cells.
b. Haversian canals are bone structures that contain blood vessels that
provide materials for the osteocytes.
c. Osteocytes have membrane extensions that protrude from bone and allow
them to exchange materials with the surrounding fluids
d. Bones are hollow in the middle and the low pressure there draws fluid
from the blood that nourishes the osteocytes.
The correct answer is b—
A. Answer a is incorrect. Bone is composed of several types of living cells
(osteoblasts, osteocytes, osteoclasts, marrow cells).
The correct answer is b—Haversian canals are bone structures that contain blood vessels
that provide materials for the osteocytes.
B. Answer b is correct.
The correct answer is b—
C. Answer c is incorrect. Osteocytes do not protrude through the bone matrix.
The correct answer is b—
D. Answer d is incorrect. Although bones are hollow (probably due to weight
considerations), the space does not create a vacuum that draws nourishment in for
osteocytes.
Challenge Questions
1. You are designing a space-exploration vehicle to perform scientific experiments
on a planet with a gravity greater than Earth’s. Given a choice between a
hydrostatic-skeleton model and an exoskeletal one, which would you choose?
Why?
Answer—Although a hydrostatic skeleton might have advantages in terms of ease of
transport and flexibility of movement, the exoskeleton would probably do a better job at
protecting the delicate instruments within. This agrees with our observations of these
support systems on Earth. Worms and marine invertebrates use hydrostatic skeletons,
although arthropods (“hard bodies”) use an exoskeleton. Worms are very flexible, but
easily crushed.
2. You start running as fast as you can. After 30 seconds or so, you settle into a
steady jog that you can easily maintain. How do the energy sources utilized by
your skeletal muscles change as you switch from sprint to jog? Why?
Answer—The first 90 seconds of muscle activity are anaerobic in which the cells utilize
quick sources of energy (creatine phosphate, lactic acid fermentation) to generate ATP.
After that, the respiratory and circulatory systems will catch up and begin delivering
more oxygen to the muscles which allows them to use aerobic respiration, which is a
much more efficient method of generating ATP from glucose.
3. The nerve gas methylphosphonofluroidic acid (Sarin) inhibits the enzyme
acetylcholinesterase, normally present in the neuromuscular junction and required
to break down acetylcholine. Based on this information, what are the likely effects
of this nerve gas on muscle function?
Answer—If acetylcholinesterase is inhibited, acetylcholine will continue to stimulate
muscles to contract. As a result, muscle twitching, and eventually paralysis, will occur. In
March 1995, canisters of Sarin were released into a subway system in Tokyo. Twelve
people were killed and hundreds injured.