HESI A2 Biology 2024

Correct Answer: B

Rationale: The correct answer is B (50%). Polydactylism is a dominant trait. If both parents have polydactylism, they must be heterozygous (Aa). When they reproduce, the Punnett square shows a 25% chance of AA, 50% chance of Aa, and 25% chance of aa offspring. Thus, 50% of their offspring are predicted to manifest the anomaly. Choice A (25%) is incorrect because that would be the percentage if both parents were homozygous dominant (AA). Choice C (75%) is incorrect because that would be the percentage if both parents were homozygous recessive (aa). Choice D (100%) is incorrect because even though both parents have the trait, they could still be carriers (Aa) and produce offspring without the anomaly.

Correct Answer: B

Rationale: The correct answer is B: Virus. A virus is a structure composed of a core of nucleic acid (either RNA or DNA) surrounded by a protein coat. This structure allows viruses to infect host cells and replicate. Blue-green algae (option C) are photosynthetic organisms composed of cells with chlorophyll. RNA (option A) is a type of nucleic acid but does not necessarily have a protein coat. Saprophytes (option D) are organisms that obtain nutrients from decaying organic matter and do not typically have a core of nucleic acid surrounded by a protein coat.

Correct Answer: B

Rationale: The correct answer is B because it involves testing the hypothesis in a controlled manner. By dividing participants into two groups with similar average blood pressure, any observed changes can be more confidently attributed to the yoga practice. Testing each participant's blood pressure after participating in a yoga class allows for individual assessment and comparison within the groups. This design helps isolate the effect of yoga on reducing blood pressure by controlling for other variables. Option A lacks a control group for comparison, making it difficult to determine if the changes in blood pressure are solely due to yoga practice. Option C introduces an additional variable (watching television) in one group, which could confound the results. Option D introduces gender as a variable, which could also affect the results. By eliminating these potential confounding factors, option B provides a more valid and reliable test of the hypothesis.

Correct Answer: A

Rationale: The correct answer is A: Red cedar. Gymnosperms are a group of seed-producing plants that do not have enclosed seeds. Red cedar is a gymnosperm because it produces naked seeds that are not enclosed in a fruit or ovary. Japanese cherry (B), Flowering dogwood (C), and American chestnut (D) are examples of angiosperms, which are seed-producing plants with enclosed seeds within a fruit or ovary. Therefore, they are not examples of gymnosperms.

Correct Answer: A

Rationale: The correct answer is A: Osmosis. High-salt content foods do not require refrigeration to prevent spoilage because salt acts as a preservative by creating a hypertonic environment that draws water out of the bacteria through osmosis, causing them to dehydrate and die. This process inhibits bacterial growth and spoilage. Choices B, C, and D are incorrect because they do not explain the specific mechanism through which salt preserves food. Diffusion, active transport, and passive transport are not directly related to the preservation of high-salt content foods.