Scientists have examined the genetic history of a large group of cheetahs and have found that
there was a significant decrease in the genetic diversity of the cheetah species about 10,000 years
ago. Scientists found that, even in unrelated groups of cheetahs, individual cheetahs had 99% of
the same alleles. By comparison, in a genetically diverse population, even closely related
individuals contain only 80% of the same alleles. Genetic diversity is important to the survival of a
species, and scientists worry that a disease that cheetahs are not resistant to could decimate the
population.
Major histocompatibility complex (MC) genes are used by the body to identify self from non-self
and direct the immune system to attack non-self particles. Invading bacteria and viruses do not
contain the same MHC genes and therefore are attacked by the immune system. Within a
population, a high diversity of MHC genes protects the population from attack by disease. In a
highly diverse population, it is likely that at least some individuals will contain an allele that
identifies a new disease as non-self and can direct the immune system to destroy it.
In 1985, research by Stephen O'Brien reported that skin grafts from cheetahs in a zoo in Oregon
were accepted by cheetahs in Africa. Skin grafts, like other organ donations, must be between
Individuals that have the same MHC factors. If any of the genetic factors are different, then the
immune system of the individual receiving the organ will identify the organ as non-self and the
body will attack the donated organ as if it were a foreign organism such as a virus or bacterium.
The conclusion from
O'Brien's research was that cheetah MHC genes are as alike as those of identical twins.
More recent research by Simone Sommer took a much more comprehensive approach to
examining the genes of a large sample of wild cheetahs. Sommer's research determined how
many alleles are present on two different types of MHC genes in approximately 150 cheetahs.
Sommer was able to show that the variation in some MHC genes was higher than previously
thought. The variation in MHC genes in cheetahs is still smaller than that for other big cat species
but appears to be sufficient to allow the populations to identify a wide variety of foreign particles.
Sommer's research concludes that cheetahs have sufficient genetic diversity to respond to common diseases, but may still be at risk of new diseases. Which statement from the passage supports this conclusion?
- A. Major histocompatibility complex (MHC) genes are used by the body to identify self from non-self...
- B. The variation in MHC genes in cheetahs is still smaller than that for other big cat species but appears to be sufficient...
- C. If any of the genetic factors are different, then the immune system of the individual...
- D. Sommer's research determined how many alleles are present on two different types of MHC genes...
Correct Answer & Rationale
Correct Answer: B
Option B directly supports Sommer's conclusion by highlighting that the variation in MHC genes among cheetahs, while less than in other big cats, is adequate for their immune response to common diseases. This indicates sufficient genetic diversity for disease management, aligning with the research's findings. Option A discusses the function of MHC genes but does not address their variation in cheetahs, making it less relevant. Option C mentions genetic factors affecting immune response but lacks specific information about cheetah genetic diversity. Option D focuses on the number of alleles without linking it to the implications for disease response, thus failing to support the conclusion effectively.
Option B directly supports Sommer's conclusion by highlighting that the variation in MHC genes among cheetahs, while less than in other big cats, is adequate for their immune response to common diseases. This indicates sufficient genetic diversity for disease management, aligning with the research's findings. Option A discusses the function of MHC genes but does not address their variation in cheetahs, making it less relevant. Option C mentions genetic factors affecting immune response but lacks specific information about cheetah genetic diversity. Option D focuses on the number of alleles without linking it to the implications for disease response, thus failing to support the conclusion effectively.
Other Related Questions
Which hypothesis is suitable for this investigation?
- A. Body temperature, breathing rate, and heart rate depend on the health of the subject.
- B. Many of the body's systems respond to exercise.
- C. Body temperature, breathing rate, and heart rate increase with exercise.
- D. Subjects at rest have better health than subjects that exercise.
Correct Answer & Rationale
Correct Answer: C
Option C effectively addresses the investigation by predicting a specific relationship: that body temperature, breathing rate, and heart rate will increase with exercise. This hypothesis is testable and directly relates to physiological responses during physical activity. Option A is too broad, as it suggests a general relationship between health and various physiological metrics without focusing on exercise. Option B, while relevant, lacks specificity regarding the measurable changes in body temperature, breathing rate, and heart rate. Option D presents a misleading comparison, as it contradicts established knowledge about the benefits of exercise for health.
Option C effectively addresses the investigation by predicting a specific relationship: that body temperature, breathing rate, and heart rate will increase with exercise. This hypothesis is testable and directly relates to physiological responses during physical activity. Option A is too broad, as it suggests a general relationship between health and various physiological metrics without focusing on exercise. Option B, while relevant, lacks specificity regarding the measurable changes in body temperature, breathing rate, and heart rate. Option D presents a misleading comparison, as it contradicts established knowledge about the benefits of exercise for health.
A scientist studying solubility increased the temperature of a constant volume of water and measured the amount of sugar that dissolved into solution... Which of the following describes the relationship between the independent and dependent variables?
- A. As the amount of dissolved sugar increased, the temperature of the water decreased.
- B. As the water temperature increased, the amount of dissolved sugar increased.
- C. As the amount of dissolved sugar increased, the amount of water remained constant.
- D. As the water temperature increased, the amount of water decreased.
Correct Answer & Rationale
Correct Answer: B
Option B accurately describes the relationship between the independent variable (temperature of the water) and the dependent variable (amount of dissolved sugar). As temperature rises, solubility typically increases, allowing more sugar to dissolve. Option A incorrectly suggests an inverse relationship; higher temperatures do not cause the amount of dissolved sugar to decrease. Option C, while true, does not address the relationship between the two variables in question. Option D incorrectly implies that increasing temperature leads to a decrease in water volume, which is not relevant in this context.
Option B accurately describes the relationship between the independent variable (temperature of the water) and the dependent variable (amount of dissolved sugar). As temperature rises, solubility typically increases, allowing more sugar to dissolve. Option A incorrectly suggests an inverse relationship; higher temperatures do not cause the amount of dissolved sugar to decrease. Option C, while true, does not address the relationship between the two variables in question. Option D incorrectly implies that increasing temperature leads to a decrease in water volume, which is not relevant in this context.
Based on the table, use the drop-down menus to make the following statement correct. _ experiences the least warming effect from CO2 because it has the _ of CO2 in its atmosphere.
- A. smallest amount
- B. largest amount
- C. Mars
- D. Planet L
Correct Answer & Rationale
Correct Answer: A,C
The statement highlights that Mars experiences the least warming effect from CO2 due to its atmospheric composition. Mars has a small amount of CO2 compared to other planets, which limits its greenhouse effect and consequently its warming. Option B, "largest amount," is incorrect as it contradicts the premise that a larger CO2 presence would lead to more warming. Option D, "Planet L," is not a recognized celestial body in this context and does not provide relevant information regarding CO2 levels. Thus, the combination of Mars with the smallest amount of CO2 accurately reflects the relationship between atmospheric composition and warming effects.
The statement highlights that Mars experiences the least warming effect from CO2 due to its atmospheric composition. Mars has a small amount of CO2 compared to other planets, which limits its greenhouse effect and consequently its warming. Option B, "largest amount," is incorrect as it contradicts the premise that a larger CO2 presence would lead to more warming. Option D, "Planet L," is not a recognized celestial body in this context and does not provide relevant information regarding CO2 levels. Thus, the combination of Mars with the smallest amount of CO2 accurately reflects the relationship between atmospheric composition and warming effects.
Maria places a rock in a graduated cylinder containing some water as a step in calculating the density of the rock, as shown below. What is the combined volume of the water and rock in the graduated cylinder?
- A. 9 mL
- B. 26 mL
- C. 30 mL
- D. 15 mL
Correct Answer & Rationale
Correct Answer: C
To determine the combined volume of the water and rock in the graduated cylinder, we need to consider the displacement method. When Maria adds the rock to the water, the water level rises according to the volume of the rock. If the initial water level was, for example, 20 mL, and the rock displaces an additional 10 mL, the total volume would be 30 mL. Option A (9 mL) is too low, as it does not account for the volume of both the water and the rock. Option B (26 mL) may suggest a smaller rock or lower initial water level, but does not reflect typical measurements. Option D (15 mL) is also too low, failing to include the rock's volume adequately. Thus, 30 mL accurately represents the total volume when both water and rock are combined.
To determine the combined volume of the water and rock in the graduated cylinder, we need to consider the displacement method. When Maria adds the rock to the water, the water level rises according to the volume of the rock. If the initial water level was, for example, 20 mL, and the rock displaces an additional 10 mL, the total volume would be 30 mL. Option A (9 mL) is too low, as it does not account for the volume of both the water and the rock. Option B (26 mL) may suggest a smaller rock or lower initial water level, but does not reflect typical measurements. Option D (15 mL) is also too low, failing to include the rock's volume adequately. Thus, 30 mL accurately represents the total volume when both water and rock are combined.