HESI A2
HESI A2 Biology 2024
1. Which animal has an open transport system?
- A. Grasshopper
- B. Earthworm
- C. Dolphin
- D. Chicken
Correct answer: B
Rationale: The correct answer is B: Earthworm. Earthworms have an open circulatory system, meaning their blood and interstitial fluid are not enclosed in blood vessels. Instead, the blood flows freely within the body cavity, allowing for direct exchange of nutrients and waste products with surrounding tissues. This lack of a closed transport system is a characteristic feature of earthworms. Choices A, C, and D are incorrect because grasshoppers, dolphins, and chickens have closed circulatory systems where the blood is enclosed within blood vessels, unlike earthworms.
2. In a strand of DNA, you would expect to see adenine paired with ___________.
- A. cytosine
- B. uracil
- C. thymine
- D. guanine
Correct answer: C
Rationale: In a strand of DNA, adenine always pairs with thymine through two hydrogen bonds. This pairing is a fundamental aspect of DNA structure, where adenine and thymine complement each other in the double helix. Choice A (cytosine) is incorrect because adenine does not pair with cytosine in DNA. Choice B (uracil) is incorrect as uracil is found in RNA, not DNA. Choice D (guanine) is incorrect as guanine pairs with cytosine, not adenine, in DNA.
3. Which of the following describes the situation where one allele takes a different form from another in a gene?
- A. phenotype
- B. heterozygous
- C. homolog
- D. homozygous
Correct answer: B
Rationale: Heterozygous is the term used to describe the genotype of an individual with two different alleles for a specific gene. In this case, one allele takes a different form from another, resulting in genetic diversity and variation in trait expression. The other choices are incorrect: 'phenotype' refers to the observable traits of an organism, 'homolog' typically refers to chromosomes that are similar in structure, and 'homozygous' describes the genotype where both alleles for a gene are the same.
4. Which of the following is necessary for cell diffusion?
- A. water
- B. membrane
- C. ATP
- D. gradient
Correct answer: D
Rationale: The correct answer is 'gradient.' In cell diffusion, substances move from an area of high concentration to an area of low concentration, driven by the concentration gradient. This process does not require water, membrane, or ATP specifically. Water can aid in the movement of substances, but it is not necessary for diffusion itself. The membrane is involved in regulating diffusion but is not a requirement for the process. ATP is not directly involved in simple diffusion processes; instead, it is more related to active transport mechanisms. Therefore, the concentration gradient is essential for cell diffusion to occur.
5. Which of the following is not true about antibiotics?
- A. They can interfere with the bacteria's ability to survive
- B. They can affect how bacteria multiply
- C. They can cause more bacteria to grow
- D. They only work on bacteria
Correct answer: C
Rationale: The correct answer is C. Antibiotics do not cause more bacteria to grow. They work by interfering with the bacteria's ability to survive, affecting how they multiply, or killing the bacteria cells. Antibiotics specifically target bacteria, so they do not promote the growth of more bacteria. Choices A, B, and D are true statements about antibiotics as they accurately describe how antibiotics work and their specific action on bacteria.
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