HESI A2 Biology Practice Test

Correct Answer: A

Rationale: The correct answer is A: Bacteria. Eukaryotic cells have a defined nucleus and membrane-bound organelles, which bacteria lack. Dogs, humans, and onions are all multicellular organisms that possess eukaryotic cells. Bacteria, being prokaryotic, do not have a distinct nucleus or membrane-bound organelles, leading to the conclusion that they do not have eukaryotic cells.

Correct Answer: D

Rationale: The correct answer is D because all the choices - the pituitary gland, the thyroid gland, and the adrenal glands - are indeed components of the endocrine system. Each of these glands secretes hormones directly into the bloodstream to regulate various bodily functions. The pituitary gland controls other endocrine glands, the thyroid gland regulates metabolism, and the adrenal glands manage stress responses. Therefore, all of these glands play vital roles in the endocrine system. The other choices (A, B, C) are incorrect because they are all components of the endocrine system.

Correct Answer: A

Rationale: The correct answer is A because water's polarity leads to hydrogen bonding, high specific heat value, and versatile solvent properties. Polarity in water results from its unequal sharing of electrons between hydrogen and oxygen atoms, creating a partial positive and negative charge. This polarity allows water molecules to form hydrogen bonds, which contribute to its high specific heat value, meaning water can absorb and release heat without drastic temperature changes. Additionally, water's polarity enables it to act as a versatile solvent, dissolving many substances. Choices B, C, and D are incorrect because they mention incorrect types of bonding and specific heat values that do not align with water's characteristics.

Correct Answer: D

Rationale: The correct answer is D because phenotype is the observable characteristics resulting from the interaction between genotype, epigenetic factors, and environmental factors. Genotype (genetic makeup) provides the foundation, epigenetic factors can modify gene expression, and environmental factors play a crucial role in shaping the final phenotype. Explanation: A: Incorrect. Phenotype is not the genetic code itself but the physical expression of genetic traits. B: Incorrect. Phenotype does not determine genotype; genotype determines phenotype. C: Incorrect. Genotype determines phenotype, not the other way around. D: Correct. Genotype, epigenetic factors, and environmental factors collectively determine the phenotype, making it the most comprehensive and accurate choice.

Correct Answer: C

Rationale: Anaerobic respiration occurs in bacteria because they live in environments with low oxygen levels. Bacteria adapt to anaerobic conditions by utilizing alternative pathways to generate energy without oxygen. This process allows them to survive and thrive in oxygen-deprived environments. The other choices are incorrect because animals require oxygen for aerobic respiration, plants use sunlight for photosynthesis, and option D is incorrect as bacteria indeed undergo anaerobic respiration in low oxygen environments.