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. Where is the site of cellular respiration in eukaryotic cells?
- A. Nucleus
- B. Chloroplasts
- C. Mitochondria
- D. Ribosomes
Correct answer: C
Rationale: The correct answer is C: Mitochondria. Mitochondria are often referred to as the powerhouse of the cell because they are responsible for cellular respiration in eukaryotic cells. During cellular respiration, mitochondria generate energy in the form of ATP. Choices A, B, and D are incorrect. The nucleus is the organelle that houses the cell's genetic material, chloroplasts are responsible for photosynthesis in plant cells, and ribosomes are involved in protein synthesis, not cellular respiration.
3. 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.
4. Dogs are part of a larger animal group, the Carnivora. What classification is this?
- A. Kingdom
- B. Class
- C. Order
- D. Genus
Correct answer: C
Rationale: The classification 'Carnivora' refers to an order in the taxonomic hierarchy. In the Linnaean classification system, the order comes below the class but above the family level. Therefore, Carnivora is a higher classification that includes dog species as well as other carnivorous mammals like cats, bears, and weasels. Option A (Kingdom) is too broad and refers to the highest taxonomic rank. Option B (Class) is a lower taxonomic rank than order. Option D (Genus) is a much more specific rank that comes below the family level in the Linnaean hierarchy.
5. The renal system consists of all the organs involved in the formation and release of urine and includes the kidneys, ureters, bladder, and urethra.
- A. The digestive system
- B. The reproductive system
- C. The renal system
- D. The kidney system
Correct answer: C
Rationale: The correct term for the system involving the organs responsible for the formation and release of urine is the renal system, not the digestive or reproductive system. The kidneys, ureters, bladder, and urethra are specifically part of the renal system, which is responsible for filtering the blood to remove waste and excess fluids, producing urine, and eliminating it from the body. The other choices, the digestive system and the reproductive system, are not responsible for the formation and release of urine, making them incorrect answers.
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