Human Body Systems Answer Key
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20. Answers in red
Stem cells present in an embryo are responsible for the formation of various
tissues and organs. Recent research suggests that it may be possible to replicate
stem cells from sections of skin taken from adult mice, rather than having to use
stem cells from the embryos of mice. In the future, human stem cells may be
used to replace human tissue damaged by diseases such as Parkinson’s disease
and multiple sclerosis.
Discuss why the use of stem cells taken from a patient to replace damaged tissues and
organs may decrease the potential risk to a patient. In your answer, be sure to:
• identify the major problem that may occur when tissues and organs donated by
another individual are used [1]… rejection of the new tissue or organ
• explain why this problem may occur [1] it has different DNA so it makes different
proteins (antigens) and the immune system attacks and tries to kill it
• explain why this problem will not occur if tissues and organs produced by stem cells
from the patient are used [1] it has the same DNA so the immune system does not try
to kill it
21. Answer in red
The table below lists enzymes that function in different locations in the human
body, and the temperature and pH ranges of these locations.
Different enzymes are secreted in each of the three locations. Ptyalin digests
carbohydrates. Pepsin and trypsin both digest proteins. Discuss the activity of these
enzymes. In your answer, be sure to:
• state how the activity of pepsin will most likely change after it moves with the food from
the stomach to the small intestine [1] it will slow down or stop
• support your answer using data from the table [1] the pH in the stomach is 1-3 but the
small intestine is 7.5-9
• state how a fever of 40°C would most likely affect the activity of these enzymes and
support your answer [1] a change in temperature would cause a change in shape of the
enzyme so the activity would slow down
• identify the characteristic of enzymes that prevents ptyalin and trypsin from digesting
the same type of food [1] specificity: one enzyme one substrate
A normally healthy 35-year-old woman was found to have a severe intestinal infection
usually seen in much older and sicker patients in hospitals. Because of so many cases
like hers, some doctors became alarmed that the organism responsible could spread
rapidly and cause unusually severe illnesses and some deaths. Scientists suspect that
the cause is a mutated form of an organism that has a resistance to some of the most
common treatments.
22. Since it is difficult to cure an infection caused by this organism, it might be easier to
prevent these infections by using a vaccine. Identify the specific material a vaccine
would have to contain to prevent future infections. [1]
Weak or dead pathogen
23. Explain how this vaccine would prevent future infections. [1] the vaccine starts an
immune response in the body to produce the antibodies to mark the infection to be killed
by the white blood cells… one antibodies are in our system, they stay forever killing
future infections before we know we have them
24. The mutated form of this type of organism could result from a change in a molecule
within one member of the original population. Identify the molecule. [1] DNA
25. Staphylococcus aureus is a type of bacterium that lives on the skin and in the
nostrils of most people. Generally, it is controlled by the immune system of the body.
Occasionally, the antibiotic penicillin is needed to control the bacterium. However, some
strains of S. aureus have a resistance to penicillin, which makes them hard to kill
and infections difficult to cure.
Explain how the resistance to penicillin affects the S. aureus population. In your answer,
be sure to include an explanation of:
• how the exposure to penicillin affects the survival of some bacteria in the population
[1] the bacteria that are not resistant die easy while those that are resistant live and
reproduce
• why the frequency of penicillin-resistant bacteria can change over time within the
population [1] those that are resistant live through the antibiotic so they can reproduce
while the non-resistant bacteria die off
• how it is still possible to cure patients who are infected with penicillin-resistant bacteria
[1] take a stronger or different antibiotic
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27. 2
28. State one possible reason why slow healing of wounds can lead to infection. [1]
The wound is open to the environment so more bacteria or viruses can get into the body
and cause infection
29. Two life functions performed by all living organisms are nutrition and respiration.
Identify two other life functions that are essential for the survival of all living organisms.
Explain how each of the two life functions you identified maintains homeostasis. [2]
Life Function: circulation
Explanation: moves needed nutrients and gases to cells and wastes away from cells
Life Function: reproduction
Explanation: lets organisms pass on their DNA
Life Function: absorption
Explanation: gets needed nutrients into the bloodstream
Many people have a sensitivity to peanuts. The symptoms can include watery, itchy
eyes and difficulty breathing. This allergic reaction can be mild, severe, or fatal.
30. Discuss why an individual can have a sensitivity to peanuts. In your answer, be
sure to:
• identify the human system that is responsible for this sensitivity to peanuts [1] immune
system
• identify the specific type of molecule that triggers an allergic reaction [1] antigen
• state one reason why a person could be allergic to peanuts, but not be allergic to
walnuts [1] they have different DNA so they make different antigens
• describe how this reaction is similar to the rejection of a transplanted organ [1] the
transplanted organ makes different chemicals (antigens) so the immune system attacks
the new organ just like an allergic reaction
Proteins on the surface of a human cell and on a bird influenza virus are represented in
the diagram below.
31. In the space below, draw a change in the bird influenza virus that would allow it to
infect this human cell. [1]
32. Explain how this change in the virus could come about. [1] a mutation in the DNA
33. Identify the relationship that exists between a virus and a human when the virus
infects the human. [1] parasitic
34. 3
35. 1
36. Explain how selective breeding is being used to try to produce commercial peanuts
that will not cause allergic reactions in people. [1] they will take the new peanuts and
mate them with another new peanut plant so they get baby peanut plants with the new
DNA
Until the middle of the 20th century, transplanting complex organs, such as kidneys,
was rarely successful. The first transplant recipients did not survive. It was not until
1954 that the first successful kidney transplant was performed. Success with transplants
increased as research scientists developed techniques such as tissue typing and the
use of immunosuppressant drugs. These are drugs that suppress the immune system to
prevent the rejection of a transplanted organ. In 2002, there were nearly 15,000 kidney
transplants performed in the United States with a greater than 95% success rate.
37. Describe the relationship of the immune system to organ transplants and the use of
immunosuppressant drugs to prevent the rejection of a transplanted organ. In your
answer be sure to:
• state one way the immune system is involved in the rejection of transplanted organs
[1] the immune system sees the new organ like a disease and tries to kill it
• explain why the best source for a donated kidney would be the identical twin of the
recipient [1] they have identical DNA so the body will not reject it
• explain why immunosuppressant drugs might be needed to prevent rejection of a
kidney received from a donor other than an identical twin [1] the drugs keep the
immune system from attacking the new organ so the body has a chance to get used to
the new organ
• state one reason a person may get sick more easily when taking an
immunosuppressant drug [1] since the immune system is not working other pathogens
can reproduce and make them sick easier
Growers of fruit trees have always had problems with insects. Insects can cause visible
damage to fruits, making them less appealing to consumers. As a result of this damage,
much of the fruit cannot be sold. Insecticides have been useful for controlling these
insects, but, in recent years, some insecticides have been much less effective. In some
cases, insecticides do nothing to stop the insect attacks.
38. Provide a biological explanation for this loss of effectiveness of the insecticides. In
your answer, be sure to:
• identify the original event that resulted in the evolution of insecticide resistance in
some insects [1] mutation or recombination of genes (just need one)
• explain why the percentage of resistant insects in the population has increased [1] the
resistant insects survive to reproduce while the non-resistant ones die
• describe one alternative form of insect control, other than using a different insecticide,
that fruit growers could use to protect their crops from insect attack [1] genetically
modify the plant to make their own insecticides or bring in a different organism that eats
those insects
Vaccines play an important role in the ability of the body to resist certain
diseases.
39. Describe the contents of a vaccine. [1] dead or weakened form of the vaccine
40. Identify the system in the body that is most directly affected by a vaccination. [1]
immune system
41. Explain how a vaccination results in the long-term ability of the body to resist
disease. The antibodies made to fight off the disease in the vaccine stay with you
forever