Question 1

In the section "Investigating Life: The Hidden Cost of Hygiene",what was the researchers' final conclusion?

Accepted Answer

The answer of In the section "Investigating Life: The Hidden...

Question 2

Why would HIV infection lead to immunodeficiency?

Accepted Answer

HIV specifically infects and destroys T helper cells, which are critical for coordinating the immune response. As the number of T helper cells declines, the immune system becomes weaker, eventually leading to immunodeficiency.

Question 3

Adaptive immune defenses provide a rapid,broad defense against any infectious agent.

Accepted Answer

Adaptive immune defenses provide a specific defense against a particular infectious agent. It takes time for the immune system to develop a specific response to a new pathogen.

Question 4

In the section "Investigating Life: The Hidden Cost of Hygiene",which of the following would a person in a less-developed country be less likely to have than a person in a more-developed country,according to the hygiene hypothesis?

Accepted Answer

The hygiene hypothesis suggests that exposure to microbes in childhood helps the immune system develop normally and reduces the risk of developing allergies and autoimmune diseases later in life. People in less-developed countries are more likely to be exposed to microbes due to poor sanitation and hygiene, making them less likely to develop conditions like asthma, which are associated with overactive immune systems. Therefore, a person in a less-developed country would be less likely to have asthma than a person in a more-developed country.

Question 5

Stem cells that give rise to white blood cells are located primarily in the thymus.

Accepted Answer

Stem cells that give rise to white blood cells are primarily located in the bone marrow, not in the thymus. The thymus is responsible for the maturation of certain types of white blood cells known as T cells.

Question 6

The presence of antibodies against HIV can be used to diagnose an infection that has occurred at least three months earlier.Why couldn't the presence of antibodies against HIV be used to diagnose a more recent infection?

Accepted Answer

It takes 2-3 months for the body to produce antibodies against HIV. Therefore, the presence of antibodies can only indicate an infection that occurred at least three months earlier and cannot be used to diagnose a more recent infection.

Question 7

In the section "Investigating Life: The Hidden Cost of Hygiene",flatworms are very thin and lack a specialized respiratory or circulatory system.How does oxygen reach their cells?

Accepted Answer

Flatworms lack specialized respiratory or circulatory systems, so oxygen reaches their cells through simple diffusion across the thin walls of their body.

Question 8

In the section "Investigating Life: The Hidden Cost of Hygiene",what is the hygiene hypothesis?

Accepted Answer

In essence,the hygiene hypothesis says that the immune system is looking for something to do,and,if not put to its normal purpose because of cleanliness,it will start to cause problems for the body.Please see sections 29.1 and 29.3 plus "Investigating Life" for more information.

Question 9

A patient can have antibodies against many strains of HIV.Which of the following is the main reason that an effective vaccine has not been produced for the HIV virus that causes AIDS?

Accepted Answer

The main reason an effective vaccine has not been produced for the HIV virus that causes AIDS is because the virus mutates rapidly, changing its outer coat. This makes it challenging to develop a vaccine that can effectively target multiple strains of the virus.

Question 10

In an autoimmune disease,the immune system attacks the body's "self antigens."

Accepted Answer

In autoimmune diseases, the immune system mistakenly identifies the body's own tissue as foreign and attacks it, resulting in damage to the body. This happens when the immune system targets self-antigens, which are proteins and other molecules that are normally present in the body.

Question 11

In the section "Investigating Life: The Hidden Cost of Hygiene",what is the independent variable in the figure?

Accepted Answer

The independent variable is the one that is manipulated or categorized to observe its effect on the dependent variable. In this case, the presence or absence of flatworm infections is the independent variable being investigated for its impact on other factors.

Question 12

In the section "Investigating Life: The Hidden Cost of Hygiene",how can the scientists further test whether flatworms can moderate the immune system?

Accepted Answer

In order to test whether flatworms can moderate the immune system, scientists can expose white blood cells to flatworm antigens, which are known to trigger the immune response. By measuring the levels of interleukin - a cytokine that mediates immune responses - after exposure to flatworm antigens, scientists can determine whether flatworms have a moderating effect on the immune response. This will provide direct evidence on whether or not flatworms can control the immune system, as hypothesized in the article. Exposing white blood cells to dust mite antigens (choice B) or measuring histamine concentrations (choices C and D) will not be as informative as these measures are not directly related to the immune system regulation by flatworms. Lastly, infecting children with flatworms (choice E) is not ethical and would involve many ethical concerns.

Question 13

Why would AIDS patients infected with HIV be at risk for opportunistic infections and rare cancers?

Accepted Answer

HIV attacks and kills the CD4+ T cells that are responsible for coordinating the immune system's response to infections and cancer. As the immune system becomes progressively weaker, opportunistic infections and rare cancers become more common since the body is less able to mount an effective response to these threats.

Question 14

If a human fetus is ___________ and the pregnant woman is ______________,an incompatibility that destroys the red blood cells of the fetus may occur.

Accepted Answer

The incompatibility that leads to destruction of fetal red blood cells is due to the Rh factor. If the fetus is Rh-positive and the mother is Rh-negative, the mother's immune system may detect the Rh factor on the fetal red blood cells as foreign and produce antibodies to attack them. This can lead to hemolytic disease of the newborn (HDN) and can cause severe anemia and jaundice in the fetus. Rh incompatibility is not related to blood type (A, B, AB, O).

Question 15

In the section "Investigating Life: The Hidden Cost of Hygiene",which of the following occurred during the coevolution of humans and pathogens that causes disease?

Accepted Answer

During the coevolution of humans and pathogens, some pathogens have evolved to produce substances that suppress our immune system, making it easier for them to cause disease. This is known as immune evasion. Option B is incorrect as not all pathogens can be destroyed by our immune system before they cause disease. Option C is also incorrect as pathogens can continue to evolve and become more infectious. Option D is incorrect as the immune system still recognizes pathogens as foreign, but some may have evolved mechanisms to evade it. Option E is also incorrect as pathogens do not have their own immune system.

Question 16

Why is there potential for a woman's body to recognize her fetus as foreign?

Accepted Answer

The fetus and mother are not genetically identical, and thus, the mother's immune system may recognize the fetus as foreign and mount an immune response against it. However, in normal pregnancies, this recognition is prevented by various mechanisms, such as immune tolerance and changes in the mother's immune system.

Question 17

In many autoimmune diseases such as lupus and rheumatoid arthritis,antibody complexes form in the blood.Kidney failure is a common consequence of these diseases for which reason?

Accepted Answer

In autoimmune diseases such as lupus and rheumatoid arthritis, antibody complexes form in the blood. These complexes can become trapped in various organs including the kidneys where they cause damage leading to kidney failure. This is why C is the best choice as the antibody complexes form in the blood but become trapped in the kidneys.

Question 18

A fever has no defense function,but acts only as a sign that an infection is present in the body.

Accepted Answer

A fever actually does have a defense function. It can assist in fighting off an infection by causing the body's immune system to become more active and speeding up the production of white blood cells. Additionally, some viruses and bacteria are less able to survive at higher temperatures, so raising the body's temperature can help to eliminate them.

Question 19

In the section "Investigating Life: The Hidden Cost of Hygiene",if a child was allergic to a substance scratched onto their skin,the area turned red and swollen within about 10 minutes.Which of the following would cause these symptoms?

Accepted Answer

The release of histamine is a common symptom of an allergic reaction, causing redness and swelling at the site of exposure.

Question 20

In the section "Investigating Life: The Hidden Cost of Hygiene",what is the dependent variable in the figure?

Accepted Answer