HESI A2
HESI A2 Biology Practice Test
1. A child is sick. They have a body temperature that exceeds 37ºC. The body senses this and begins to sweat in order to lower the temperature. What is this an example of?
- A. Positive feedback loop
- B. Negative feedback loop
- C. Both
- D. None of the above
Correct answer: B
Rationale: This is an example of a negative feedback loop. In a negative feedback loop, the body's response (sweating) works to counteract the initial stimulus of a high body temperature by cooling the body down. The goal is to return the body to homeostasis, maintaining a stable internal environment. Positive feedback loops amplify the initial stimulus rather than counteracting it, which is not the case here. Therefore, choices A and C are incorrect. Choice D is also incorrect as the situation described fits the characteristics of a negative feedback loop.
2. How do green plants use nitrates in the nitrogen cycle?
- A. To synthesize proteins
- B. To store food
- C. To decompose ammonia
- D. To break down nitrites
Correct answer: A
Rationale: Green plants use nitrates in the nitrogen cycle to synthesize proteins. Nitrogen is an essential component of amino acids, which are the building blocks of proteins. Plants take up nitrates from the soil through their roots and incorporate nitrogen into their proteins through the process of protein biosynthesis. This helps in their growth, development, and overall health. Choice B, 'To store food,' is incorrect because nitrates are primarily used for protein synthesis, not food storage. Choice C, 'To decompose ammonia,' is incorrect as plants do not decompose ammonia but rather utilize it through nitrification. Choice D, 'To break down nitrites,' is incorrect as plants typically convert nitrites into nitrates through a process called nitrate assimilation for protein synthesis.
3. 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.
4. What is the second part of an organism’s scientific name?
- A. species
- B. phylum
- C. population
- D. kingdom
Correct answer: A
Rationale: The correct answer is 'species.' In binomial nomenclature, the second part of an organism's scientific name represents its species. The species name is a unique identifier within the genus and helps differentiate between different organisms within the same genus. Choices B, C, and D are incorrect. Phylum is a taxonomic rank higher than species, population refers to a group of organisms of the same species living in the same area, and kingdom is a taxonomic rank higher than genus.
5. 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'.
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