HESI A2
Biology HESI A2 Practice Test
1. Tonicity refers to the movement of:
- A. Water
- B. Solute
- C. Cells
- D. None of the above
Correct answer: A
Rationale: Tonicity refers to the movement of water across a membrane in response to differences in solute concentration. In a hypertonic solution, where there is a higher concentration of solutes outside the cell, water will move out of the cell to try to reach equilibrium. In a hypotonic solution, where there is a lower concentration of solutes outside the cell, water will move into the cell to balance the concentrations. Cells and solutes themselves do not actively move in response to tonicity; it is the movement of water that helps achieve equilibrium. Therefore, the correct answer is water (Choice A). Choices B, C, and D are incorrect as tonicity specifically refers to water movement and not the movement of solutes, cells, or none of the above.
2. The phases of mitosis include:
- A. Prophase, interphase, metaphase, anaphase, and telophase
- B. Prophase, prophase, metaphase, anaphase, and cytokinesis
- C. Prophase, prometaphase, metaphase, anaphase, and telophase
- D. Prophase, interphase, prophase, anaphase, and telophase
Correct answer: C
Rationale: The correct phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase. Prophase is the first phase where chromatin condenses into chromosomes, the nuclear envelope breaks down, and the mitotic spindle forms. Prometaphase follows prophase, involving the full disintegration of the nuclear envelope and the attachment of spindle fibers to the kinetochores of the chromosomes. Metaphase is where chromosomes align along the metaphase plate. Anaphase is the phase where sister chromatids separate and move towards opposite poles. Telophase marks the final stage of mitosis, involving the decondensation of chromosomes and the reformation of the nuclear envelope. Choice A is incorrect because it includes interphase, which is not a phase of mitosis. Choice B is incorrect as it repeats prophase, which is the initial phase. Choice D is incorrect because it includes interphase and repeats prophase.
3. Which cellular structure is found in animal cells but not in plant cells?
- A. Centriole
- B. Cytoplasm
- C. Vacuole
- D. Golgi apparatus
Correct answer: A
Rationale: The correct answer is A, Centriole. Centrioles are found in animal cells but not in plant cells. They play a crucial role in organizing microtubules during cell division, aiding in the formation of the mitotic spindle. Plant cells lack centrioles; instead, they utilize microtubule organizing centers to perform similar functions during cell division. Choices B, C, and D are incorrect because cytoplasm is a part of both animal and plant cells, vacuoles are found in plant cells and some animal cells, and the Golgi apparatus is present in both types of cells.
4. Which is true of the term Phenotype?
- A. It is the genetic code
- B. Phenotype determines genotype
- C. Genotype determines phenotype
- D. Genotype, epigenetic factors, and environmental factors determine phenotype
Correct answer: D
Rationale: The term "phenotype" refers to the observable characteristics or traits of an organism, which are determined by a combination of genotype (genetic makeup), epigenetic factors (modifications to gene expression), and environmental factors (external influences and experiences). Genotype, epigenetic factors, and environmental factors all play a role in determining an individual's phenotype, making option D the correct statement. Options A, B, and C are incorrect because the phenotype is not the genetic code, the phenotype does not determine the genotype, and it is the genotype that influences the phenotype, not the other way around.
5. Which part of a plant’s reproductive system is of a different “gender” than the others?
- A. Stamen
- B. Pistil
- C. Stigma
- D. Style
Correct answer: A
Rationale: The stamen is the male reproductive organ of a plant, producing pollen grains. The pistil, consisting of the stigma, style, and ovary, is the female reproductive organ. Therefore, the stamen is of a different 'gender' than the other parts of the plant's reproductive system. The pistil, stigma, and style are all part of the female reproductive system, involved in receiving pollen and supporting fertilization. Stamen is the correct answer as it is the male part of a plant's reproductive system, making it different 'gender-wise' from the female parts.
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