Biology HESI A2 Practice Test

Correct Answer: A

Rationale: Adenine is a purine base because it has a double-ring structure, which is a characteristic of purines. It pairs with thymine in DNA and uracil in RNA. Cytosine, thymine, and guanine are pyrimidines, which have a single-ring structure. Therefore, the correct answer is A. Cytosine, thymine, and guanine are incorrect choices as they are pyrimidines.

Correct Answer: A

Rationale: The correct answer is A: Atmospheric pressure. Atmospheric pressure is the force per unit area exerted by the weight of the air above a surface in Earth's atmosphere. This pressure is due to the gravitational pull on the air molecules. B: Barometric density is not the correct term. Density refers to the mass of a substance per unit volume, not the force per unit area. C: Aneroid pressure is not a valid term related to the given concept. Aneroid barometers are devices used to measure atmospheric pressure, not a type of pressure itself. D: Barometric pressure is a commonly used term synonymous with atmospheric pressure in the context of weather measurements. However, the term "atmospheric pressure" is more precise and directly correlates with the weight of the air above a surface.

Correct Answer: C

Rationale: Correct Answer: C Rationale: 1. Sexual reproduction involves two cells (sperm and egg) contributing genetic material to offspring, leading to genetic variation. 2. Greater genetic variation in offspring helps in adapting to changing environments and enhances species survival. 3. Asexual reproduction involves a single parent cell dividing to produce genetically identical offspring. 4. Option A is incorrect as sexual reproduction does not result in half of the cells being identical to the original cell. 5. Option B is incorrect as asexual reproduction does not result in greater variation, it produces genetically identical offspring. 6. Option D is incorrect as sexual reproduction involves two cells contributing genetic material, leading to variation.

Correct Answer: B

Rationale: The correct answer is B: They lower the activation energy needed. Enzymes lower the activation energy required for a reaction to occur, facilitating the reaction without being consumed in the process. This is crucial in speeding up biological processes. Choices A, C, and D are all true statements about enzymes. A: Enzymes catalyze reactions by speeding up the rate of a chemical reaction. C: Enzymes have an active site where substrate molecules bind, facilitating the reaction. D: Enzymes are typically proteins, although some RNA molecules can also exhibit catalytic activity.

Correct Answer: C

Rationale: The correct answer is C: Producing blood. The skeletal system does not produce blood; that is the function of the bone marrow within the bones. The other choices are functions of the skeletal system: A) Providing shape and form by supporting soft tissues, B) Supporting and protecting the body by providing structure and protecting internal organs, D) Storing vitamins like calcium and phosphorus for bone health. Thus, option C is the correct answer as it does not directly relate to the functions of the skeletal system.