HESI A2
HESI A2 Biology 2024
1. Dogs are part of a larger animal group, the Carnivora. What classification is this?
- A. Kingdom
- B. Class
- C. Order
- D. Genus
Correct answer: C
Rationale: The classification 'Carnivora' refers to an order in the taxonomic hierarchy. In the Linnaean classification system, the order comes below the class but above the family level. Therefore, Carnivora is a higher classification that includes dog species as well as other carnivorous mammals like cats, bears, and weasels. Option A (Kingdom) is too broad and refers to the highest taxonomic rank. Option B (Class) is a lower taxonomic rank than order. Option D (Genus) is a much more specific rank that comes below the family level in the Linnaean hierarchy.
2. Which of the following cell types has no nucleus?
- A. platelet
- B. red blood cell
- C. white blood cell
- D. phagocyte
Correct answer: B
Rationale: The correct answer is B, red blood cell. In humans, red blood cells do not have a nucleus. This unique feature allows them to have more space to carry oxygen efficiently. Platelets (choice A), white blood cells (choice C), and phagocytes (choice D) all have nuclei. Platelets are cell fragments, while white blood cells and phagocytes are types of immune cells that contain a nucleus for DNA and cellular functions.
3. Which two bases are purines?
- A. Adenine (A)
- B. Cytosine (C)
- C. Thymine (T)
- D. Guanine (G)
Correct answer: A
Rationale: Adenine (A) and guanine (G) are the two bases that are purines. Purines are characterized by a double-ring structure containing two carbon rings, distinguishing them from pyrimidines. Adenine and guanine are purines because they possess this unique double-ring structure. Therefore, choices A and D, adenine and guanine, respectively, are the correct answers. Choices B and C, cytosine and thymine, are pyrimidines and do not exhibit the double-ring structure characteristic of purines.
4. Which is not a step in the water cycle?
- A. Condensation
- B. Transpiration
- C. Nitrification
- D. Absorption
Correct answer: C
Rationale: Nitrification is a biological process in the nitrogen cycle where ammonia is converted into nitrites and then nitrates by bacteria. It is not a step in the water cycle. The water cycle involves processes like evaporation, condensation, precipitation, and transpiration that are related to the movement and transformation of water in the environment. Choices A, B, and D are all part of the water cycle: condensation is the process where water vapor turns into liquid water, transpiration is the release of water vapor by plants, and absorption refers to the process of water being taken in by soil or other materials.
5. Phenotype refers to the _ of an individual.
- A. Genetic makeup
- B. Actual physical appearance
- C. Recessive alleles
- D. None of the above
Correct answer: B
Rationale: Phenotype refers to the actual physical appearance and characteristics of an individual, which are determined by the interaction of both genetic makeup (genotype) and environmental factors. It includes visible traits such as height, eye color, and hair type. Choice A, genetic makeup, refers to the genotype, which is the genetic constitution of an organism. Choice C, recessive alleles, is a specific type of gene variant and does not encompass the entire concept of phenotype. Choice D, none of the above, is incorrect as phenotype does refer to the actual physical appearance of an individual.
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