HESI A2
HESI A2 Practice Test Biology
1. How many different types of nucleotides are there in DNA?
- A. one
- B. two
- C. four
- D. eight
Correct answer: C
Rationale: The correct answer is 'C: four.' DNA is composed of four different types of nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides pair up in specific combinations to form the genetic code. Choices 'A: one,' 'B: two,' and 'D: eight' are incorrect because DNA consists of a set of four distinct nucleotides, not one, two, or eight.
2. Within the biological hierarchical system of organization, which of the following is least inclusive?
- A. phylum
- B. order
- C. kingdom
- D. species
Correct answer: D
Rationale: The correct answer is 'D: species.' In the biological hierarchical system of organization, a species is the least inclusive level. A species consists of organisms that share similar characteristics and can interbreed to produce fertile offspring. On the other hand, a phylum, order, and kingdom are more inclusive classifications that encompass multiple species. Phylum groups together related classes, order groups together related families, and kingdom groups together related phyla. Therefore, species is the least inclusive category within the biological hierarchical system.
3. What is the term for the movement of ions and other molecular substances across cell membranes without the need for energy?
- A. Active Transport
- B. Passive Transport
- C. Diffusion
- D. Osmosis
Correct answer: B
Rationale: Passive transport refers to the movement of substances across cell membranes without the need for energy input. In contrast, active transport, choice A, requires energy to move substances against their concentration gradient. Diffusion, choice C, is a type of passive transport where substances move from an area of high concentration to low concentration. Osmosis, choice D, specifically refers to the movement of water molecules across a selectively permeable membrane.
4. 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.
5. Which of the following is a tertiary consumer?
- A. Owl
- B. Shrew
- C. Grasshopper
- D. Wheat
Correct answer: A
Rationale: The correct answer is A, Owl. Tertiary consumers are organisms that feed on secondary consumers, which, in turn, feed on primary consumers. Owls are considered tertiary consumers because they primarily feed on animals such as rodents, which are secondary consumers. Shrew (choice B) is a secondary consumer, feeding on insects and worms, placing it at a lower trophic level than the owl. Grasshopper (choice C) is a primary consumer, feeding on plants. Wheat (choice D) is not a consumer in the food chain but a plant.
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