HESI A2
HESI A2 Biology Practice Test
1. The procedure to focus an image using a compound microscope involves
- A. Adjusting the coarse adjustment each time a new magnification is selected
- B. Adjusting the fine adjustment each time a new magnification is selected
- C. Adjusting the stage each time a new magnification is selected
- D. All of the above
Correct answer: B
Rationale: When using a compound microscope, it is essential to adjust the fine adjustment knob each time you switch to a new magnification level. The fine adjustment knob allows for precise focusing on the specimen at different magnifications, ensuring a clear and sharp image. The coarse adjustment knob is typically used only at the lower magnification settings to bring the image into view roughly. Adjusting the stage may be necessary based on the size and thickness of the specimen, but it does not need to be done every time a new magnification is selected. Therefore, option B is the correct choice as it focuses on the key aspect of precise focusing during magnification changes.
2. Imagine that two parents both carry the recessive gene for cystic fibrosis. Any homozygous recessive offspring will manifest the disease. What percentage of the offspring is predicted to be carriers but not manifest the disease?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: B
Rationale: When both parents carry the recessive gene for cystic fibrosis (homozygous recessive), there is a 25% chance for each offspring to inherit two recessive alleles and, therefore, manifest the disease. There is also a 50% chance for each offspring to inherit one recessive allele and one dominant allele, making them carriers of the disease but not manifest it. Therefore, 25% of the offspring are predicted to be carriers but not manifest the disease. Choice A (0%) is incorrect because there is a portion of offspring that will be carriers. Choice C (50%) is incorrect as this percentage corresponds to carriers who will not manifest the disease. Choice D (100%) is incorrect as not all offspring will be carriers and not manifest the disease.
3. What process involves the movement of water molecules through a selectively permeable membrane?
- A. Diffusion
- B. Osmosis
- C. Active Transport
- D. Facilitated Diffusion
Correct answer: B
Rationale: Osmosis is the process specifically involving the movement of water molecules through a selectively permeable membrane, from an area of higher water concentration to an area of lower water concentration. This process helps balance concentrations on both sides of the membrane. Choice A, Diffusion, refers to the movement of particles from an area of higher concentration to an area of lower concentration, not specific to water. Choice C, Active Transport, requires energy to move substances against their concentration gradient, unlike osmosis. Choice D, Facilitated Diffusion, involves the use of transport proteins to move specific substances across membranes, not limited to water molecules.
4. Which gives the order of four taxonomic categories from least to most specific?
- A. Kingdom, phylum, class, order
- B. Kingdom, phylum, order, class
- C. Kingdom, order, phylum, class
- D. Kingdom, class, order, phylum
Correct answer: A
Rationale: The correct order of the four taxonomic categories from least to most specific is Kingdom, phylum, class, and order. This sequence adheres to the hierarchical system of classification where organisms are grouped based on shared characteristics, becoming more specific as you move from Kingdom to order. Choice B is incorrect as the order of 'order' and 'class' is swapped. Choice C is incorrect as 'order' precedes 'phylum' instead of following it. Choice D is incorrect as 'class' should come before 'order'.
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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