HESI A2
Biology HESI A2 Practice Exam
1. How should a researcher test the hypothesis that a particular species of bird vocalizes most in the hours around dawn?
- A. Observe a flock of the birds in captivity and record them at two-hour intervals from predawn until sunset for a month.
- B. Observe a flock of the birds in the wild and record them at one-hour intervals from predawn until sunset in several seasons.
- C. Observe a flock of the birds in the wild and record them in predawn and postdawn hours every day for six months.
- D. Observe a flock of the birds in the wild, record them at one-hour intervals for a month, and compare that recording to recordings of other species.
Correct answer: C
Rationale: Observing a flock of the birds in the wild and recording them in predawn and postdawn hours every day for six months would be the best way to test the hypothesis that a particular species of bird vocalizes most in the hours around dawn. This method allows for consistent monitoring of the birds during specific times of interest over an extended period, providing a comprehensive dataset to accurately analyze the vocalization patterns. Options A and B do not focus specifically on dawn hours, making them less suitable for testing the hypothesis. Option D introduces a comparison with other species, which is unnecessary and distracts from the main objective of studying the vocalization pattern of the particular bird species around dawn.
2. Cytosine and thymine are known as:
- A. Purines
- B. Pyrimidines
- C. Both
- D. None of the above
Correct answer: B
Rationale: Cytosine and thymine are known as pyrimidines because they have a single carbon ring structure. Purines, on the other hand, have a double-ring structure. Choice A ('Purines') is incorrect because purines have a double-ring structure, unlike cytosine and thymine. Choice C ('Both') is incorrect as it implies they are both purines and pyrimidines, which is not true. Choice D ('None of the above') is incorrect because cytosine and thymine are indeed pyrimidines.
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. What is the typical result of mitosis in humans?
- A. two diploid cells
- B. two haploid cells
- C. four diploid cells
- D. four haploid cells
Correct answer: A
Rationale: The correct answer is A: two diploid cells. Mitosis is a type of cell division that results in two daughter cells, each having the same number of chromosomes as the parent cell. In humans, the typical result of mitosis is the formation of two diploid cells, not haploid or four cells. Choice B, two haploid cells, is incorrect because mitosis produces genetically identical diploid cells. Choices C and D, four diploid cells and four haploid cells, respectively, are incorrect as mitosis results in two daughter cells, not four.
5. What type of cells are involved in meiosis (sex cells)?
- A. Somatic Cells
- B. Gametes
- C. Zygote
- D. Diploid Cells
Correct answer: B
Rationale: The correct answer is B, Gametes. Gametes are the specialized sex cells involved in meiosis, such as sperm and eggs. Somatic cells (A) are non-reproductive cells found in the body, not involved in meiosis. Zygote (C) is the result of fertilization, formed when gametes unite. Diploid cells (D) have two sets of chromosomes, but in meiosis, gametes are produced through a process of cell division that reduces the chromosome number by half to haploid.
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