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Which element's neutral atom has 2 electrons in the first shell and 6 electrons in the second shell of the electron cloud?
- A. Beryllium
- B. Carbon
- C. Helium
- D. Oxygen
Correct Answer: D
Rationale: The correct answer is Oxygen. Oxygen has a total of 8 electrons, with 2 in the first shell and 6 in the second shell. This configuration matches the description provided in the question. Choice A, Beryllium, has 2 electrons in total, so it cannot have 2 in the first shell and 6 in the second. Choice B, Carbon, has 6 electrons in total, so it also does not match the given electron distribution. Choice C, Helium, has only 2 electrons in total and therefore does not fit the electron configuration described in the question.
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What is a benefit of a taxonomic system?
- A. Researchers can describe how living things behave.
- B. Researchers can develop names for new organisms.
- C. Living things can be distinguished from nonliving things.
- D. Living things can be classified based on their molecular traits.
Correct Answer: D
Rationale: The correct answer is D. A taxonomic system allows scientists to classify living organisms based on their molecular and genetic traits. This classification helps in understanding the relationships and evolutionary history of different organisms, providing insights into their characteristics and behaviors. Choices A, B, and C do not directly relate to the primary purpose and benefit of a taxonomic system, which is the systematic classification of organisms.
Which term is used interchangeably with negative variation?
- A. Non-correlation
- B. Direct correlation
- C. Inverse correlation
- D. Positive correlation
Correct Answer: C
Rationale: The correct answer is C: Inverse correlation. Negative variation is synonymous with inverse correlation, indicating that as one variable increases, the other decreases. This relationship is the opposite of positive correlation, where both variables increase or decrease together. Non-correlation and direct correlation do not convey the concept of negative variation and are not interchangeable terms in this context. Non-correlation refers to variables that are not related or associated, while direct correlation indicates that as one variable increases, the other also increases. Positive correlation describes a relationship where both variables increase together, which is the opposite of negative variation.
If a doctor diagnoses a patient with an impaired posterior pituitary gland, which of the following symptoms related to kidney function does the patient display?
- A. Thirst
- B. Tiredness
- C. Weight gain
- D. Concentrated urine
Correct Answer: D
Rationale: When the posterior pituitary gland is impaired, there is decreased secretion of antidiuretic hormone (ADH). ADH plays a crucial role in regulating water reabsorption by the kidneys. A deficiency of ADH leads to the inability of the kidneys to concentrate urine, resulting in the production of dilute urine. Therefore, 'Concentrated urine' is the correct symptom associated with impaired posterior pituitary gland. Choices A, B, and C are incorrect. Thirst is more commonly associated with diabetes insipidus, tiredness could be a general symptom but not specifically related to kidney function, and weight gain is not a typical symptom of impaired posterior pituitary gland affecting kidney function.
What two factors enable some intercellular chemical signals to diffuse across cell membranes and bind to intracellular receptors?
- A. They are small and soluble.
- B. They are large and soluble.
- C. They are small and insoluble.
- D. They are large and insoluble.
Correct Answer: A
Rationale: The correct answer is A: 'They are small and soluble.' Small and soluble molecules can easily pass through cell membranes and bind to intracellular receptors. Being small allows them to pass through the membrane, while being soluble enables them to dissolve in the aqueous environment inside the cell. Choice B is incorrect because large molecules typically cannot pass through the cell membrane easily. Choices C and D are incorrect because insoluble molecules would not dissolve in the aqueous environment inside the cell, hindering their ability to bind to intracellular receptors.
How do killer T cells recognize infected cells?
- A. The B cells flag the infected cells with amino acids.
- B. Tiny bits of the virus's RNA are left around the cell.
- C. Macrophages show up to help consume the infected cell.
- D. The T cells have receptors that recognize the proteins the virus leaves on the surface of the cell.
Correct Answer: D
Rationale: Killer T cells recognize infected cells by detecting viral proteins displayed on the surface of these cells. The T cells possess receptors specifically designed to identify these viral proteins, allowing them to target and eliminate the infected cells. Choice A is incorrect because B cells are not directly involved in the recognition process of infected cells by killer T cells. Choice B is incorrect because tiny bits of the virus's RNA being left around the cell is not how killer T cells primarily recognize infected cells. Choice C is incorrect because while macrophages play a role in immune responses, they do not directly assist in the recognition of infected cells by killer T cells.