HESI A2
HESI A2 Biology 2024
1. ___________ is a symbiotic relationship in which one organism benefits and the other is not affected.
- A. Mutualism
- B. Parasitism
- C. Commensalism
- D. Competition
Correct answer: C
Rationale: The correct answer is 'Commensalism.' In commensalism, one organism benefits from the relationship while the other is neither helped nor harmed. This type of symbiotic relationship is characterized by one organism deriving a benefit, such as food or shelter, without impacting the other organism in any significant way. Choice A, 'Mutualism,' is a symbiotic relationship in which both organisms benefit. Choice B, 'Parasitism,' is a symbiotic relationship in which one organism benefits at the expense of the other. Choice D, 'Competition,' refers to a relationship in which organisms compete for limited resources, with both being affected in terms of access to resources.
2. 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.
3. What type of transport moves substances across the cell membrane using energy?
- A. Passive Transport
- B. Active Transport
- C. Facilitated Diffusion
- D. Osmosis
Correct answer: B
Rationale: The correct answer is B: Active Transport. Active transport moves substances across the cell membrane by utilizing energy from the cell, typically in the form of ATP. This process allows the cell to move molecules against their concentration gradient, requiring energy expenditure. Choices A, C, and D are incorrect because passive transport does not require energy input, facilitated diffusion involves the assistance of proteins but does not directly use energy, and osmosis is the diffusion of water molecules specifically, not substances, across a selectively permeable membrane.
4. Which, if any, of the following statements about the biosphere is correct?
- A. The biosphere is the part of the Earth that supports life.
- B. The biosphere encompasses the entire surface of the Earth.
- C. A and B are correct.
- D. None of these statements is correct.
Correct answer: A
Rationale: Statement A is correct. The biosphere refers to the part of the Earth where life exists, including the land, water bodies, and atmosphere. It is the zone where living organisms and ecosystems exist. Statement B is incorrect because the biosphere covers various ecosystems on Earth but does not encompass the entire surface of the planet. The biosphere includes regions such as the lithosphere (land), hydrosphere (water bodies), and atmosphere, but not every part of the Earth's surface. Therefore, option C, stating both A and B are correct, is inaccurate. The correct answer is option A, as it accurately defines the biosphere.
5. Which of the following organelles is responsible for producing ATP in cells?
- A. Nucleus
- B. Mitochondrion
- C. Chloroplast
- D. Lysosome
Correct answer: B
Rationale: The correct answer is 'Mitochondrion.' Mitochondria are known as the powerhouse of the cell and are responsible for producing ATP, the energy currency of the cell. The nucleus is responsible for storing genetic material and controlling cell activities, not for ATP production. Chloroplasts are found in plant cells and are responsible for photosynthesis, not ATP production. Lysosomes are involved in digestion and waste removal, not ATP production.
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