HESI A2
HESI A2 Biology 2024
1. A student was asked to count birds in a given location over a 24-hour period. Which count would make their data most valid?
- A. Count birds at one feeder every 6 hours.
- B. Count birds at three feeders at noon and 6:00 P.M.
- C. Count birds at one feeder at noon and 6:00 P.M.
- D. Count birds at three feeders every 6 hours.
Correct answer: C
Rationale: Counting birds at one feeder at consistent time intervals (noon and 6:00 P.M.) over a 24-hour period ensures that the data collected are evenly distributed and provide a more accurate representation of the bird population in that location throughout the day. This method allows for observations during different times of the day, capturing potential variations in bird activity and distribution. Choice A is not as effective as it lacks observations at different times of the day, potentially missing variations in bird behavior. Choice B involves multiple locations and times, which could introduce more variables and make it harder to analyze the data accurately. Choice D, counting birds at three feeders every 6 hours, may provide too frequent data points and not cover all significant time intervals for observing bird activity.
2. What is the magnification of an ocular lens on a microscope?
- A. 4x
- B. 10x
- C. 40x
- D. 100x
Correct answer: B
Rationale: The magnification of an ocular lens on a microscope is typically 10x, which is considered standard for most microscopes. Ocular lenses are designed to magnify the image produced by the objective lens further. Choices A, C, and D are incorrect because they do not represent the standard magnification of an ocular lens. A magnification of 4x, 40x, or 100x would not be typical for an ocular lens in a microscope.
3. In an example of a male with hemophilia and a female carrier, what percentage of the offspring is predicted to be carriers only?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: C
Rationale: In this scenario, the male offspring will inherit the X chromosome with the hemophilia gene from the mother, as males have one X chromosome inherited from their mother. The female offspring will inherit one normal X chromosome from the father and one X chromosome with the hemophilia gene from the mother, making them carriers of the hemophilia trait. Therefore, 50% of the offspring will be carriers only. Option A (0%) is incorrect as female offspring will inherit the X chromosome with the hemophilia gene from the mother. Option B (25%) is incorrect as the female offspring will not be unaffected. Option D (100%) is incorrect as not all offspring will be carriers, only the female offspring.
4. Choose the two bases that have two carbon rings:
- A. Adenine
- B. Cytosine
- C. Thymine
- D. Guanine
Correct answer: A
Rationale: Adenine and guanine have two carbon rings and are known as purines. These bases are found in nucleic acids such as DNA and RNA. Adenine (option A) and guanine (option D) are the correct choices as they both have two carbon rings in their molecular structure. Cytosine (option B) and thymine (option C) have a single carbon ring each, making them incorrect choices for bases with two carbon rings.
5. Which, if any, of the following statements are true?
- A. Water boils at approximately 100°C (212°F) at standard atmospheric pressure
- B. The boiling point is the temperature at which the vapor pressure is higher than the atmospheric pressure around the water
- C. Water boils at a lower temperature in areas of lower pressure
- D. A and C are true
Correct answer: D
Rationale: Both statements A and C are true. Water indeed boils at approximately 100°C (212°F) at standard atmospheric pressure. However, water boils at a lower temperature in areas of lower pressure due to the decreased atmospheric pressure, which affects the vapor pressure and boiling point of water. Statement B is incorrect because the boiling point is the temperature at which the vapor pressure equals the external pressure (atmospheric pressure in this case), not when it is higher.
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