HESI A2 Biology 2024

Correct Answer: B

Rationale: The correct answer is B because enzymes speed up chemical reactions by lowering the activation energy required for the reaction to occur. This is achieved by binding to the substrate, forming an enzyme-substrate complex, and facilitating the conversion of substrate into product. Enzymes do not slow down or stop reactions, as suggested in choices A and D. Choice C is incorrect as enzymes play a crucial role in catalyzing reactions.

Correct Answer: A

Rationale: The correct answer is A: Mutualism. This is because mutualism is a symbiotic relationship where both organisms benefit. In this type of relationship, both organisms obtain advantages such as food, protection, or other resources. On the other hand, choices B, C, and D are incorrect. Parasitism (B) involves one organism benefiting at the expense of the other. Commensalism (C) is a relationship where one organism benefits while the other is neither helped nor harmed. Competition (D) is a relationship where organisms compete for limited resources, resulting in one or both organisms being negatively affected. Thus, the most suitable term for a relationship where both organisms benefit is mutualism.

Correct Answer: A

Rationale: During anaphase, the correct answer is A because it is the phase where chromosomes move to opposite ends of the spindle. This separation ensures that each new cell receives a complete set of chromosomes. Choice B is incorrect because nuclear membrane and nucleoli disintegrate during prophase, not anaphase. Choice C is incorrect as chromatids line up at the center of the spindle during metaphase. Choice D is incorrect as the nuclear membrane and nucleoli do not form during anaphase but rather re-form during telophase.

Correct Answer: D

Rationale: The correct answer is D (2 females : 1 male) because in this scenario, the male offspring will inherit the X chromosome without the hemophilia gene from the mother. The female offspring will inherit one X chromosome with the hemophilia gene from the carrier mother and one X chromosome without the gene from the father. Therefore, 2 out of 3 offspring are predicted neither to carry nor manifest the disease. Choice A (0 females : 1 male) is incorrect because females can also be carriers of hemophilia. Choice B (1 female : 1 male) is incorrect because it doesn't account for the possibility of female carriers. Choice C (1 female : 0 males) is incorrect because it doesn't consider the transmission of the X chromosome from the mother to the sons.

Correct Answer: C

Rationale: The correct answer is C: Order. Classification starts from the broadest category (Kingdom) to the most specific (Genus). Carnivora is an Order in the classification hierarchy, encompassing various families of carnivorous mammals, including dogs. Therefore, the correct classification for dogs within the Carnivora group is Order. Choices A, B, and D are incorrect because Kingdom refers to the highest taxonomic rank, Class is a level below Order, and Genus is a more specific category than Order.