HESI A2
Biology HESI A2 Practice Exam
1. 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.
2. What are the three main events of the haploid cell cycle?
- A. DNA replication, mitosis, and cytokinesis
- B. DNA replication, meiosis, and cytokinesis
- C. DNA replication, cytokinesis, and degradation
- D. Mitosis, meiosis, and apoptosis
Correct answer: A
Rationale: In the haploid cell cycle, the three main events are DNA replication, where the cell's genetic material is duplicated; mitosis, which is the division of the nucleus to ensure each daughter cell receives a complete set of chromosomes; and cytokinesis, the division of the cell cytoplasm to separate the two daughter cells. Meiosis is not part of the haploid cell cycle as it occurs in diploid cells to produce haploid gametes. Apoptosis is a process of programmed cell death and is not a routine event in the cell cycle. Therefore, the correct answer is A. Choices B, C, and D are incorrect as meiosis and apoptosis are not part of the haploid cell cycle, and degradation is not a typical event in the cell cycle.
3. How does water affect the temperature of a living thing?
- A. Water increases temperature.
- B. Water keeps temperature stable.
- C. Water decreases temperature.
- D. Water does not affect temperature.
Correct answer: B
Rationale: Water has a high specific heat capacity, which means it can absorb and release large amounts of heat with minimal temperature change. This property helps water regulate the temperature of living things by maintaining a stable environment. Choice A is incorrect because water does not consistently increase temperature, but rather helps in temperature regulation. Choice C is incorrect as water doesn't typically decrease temperature in living organisms. Choice D is incorrect since water does play a crucial role in regulating temperature.
4. 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.
5. Cells that line the inner or outer surfaces of organs or body cavities are often linked together by intimate physical connections. These connections are referred to as ______.
- A. Separate desmosomes
- B. Ronofilaments
- C. Tight junctions
- D. Fascia adherens
Correct answer: C
Rationale: The correct answer is C: Tight junctions. Tight junctions, also known as zonula occludens, are the intimate physical connections between cells that line the inner or outer surfaces of organs or body cavities. These junctions form a virtually impermeable barrier to fluid, creating a tight seal between the cells. This helps in maintaining the integrity and function of the tissue as well as regulating the movement of substances across the cell layer. Choice A, Separate desmosomes, are cell structures that provide strong adhesion between cells but do not create a barrier to fluid. Choice B, Ronofilaments, is not a term used to describe the connections between cells. Choice D, Fascia adherens, are another type of cell junction involved in cell adhesion, but they are different from tight junctions in terms of their structure and function.
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