Biology HESI A2 Practice Exam

Correct Answer: C

Rationale: The correct answer is C: Commensalism. In this scenario, the cattle benefit from having the insects controlled by the cattle egrets, while the cattle egrets benefit from the insects stirred up by the cattle. The cattle are unaffected by the presence of the egret, making it a one-sided relationship where one species benefits (egrets) while the other is neither harmed nor helped (cattle). This is a classic example of commensalism, where one species benefits while the other remains unaffected. A: Mutualism refers to a relationship where both species benefit, which is not the case here. B: Parasitism involves one species benefiting while the other is harmed, which is not the case in this scenario. D: Competition occurs when two or more species compete for limited resources, which is not the case here as the cattle and cattle egrets are not competing but rather benefiting from each other's presence.

Correct Answer: C

Rationale: The correct answer is C: Cell membrane. The cell membrane acts as a protective barrier, regulating the passage of substances in and out of the cell. It provides structural support and helps maintain cell integrity. Mitochondria (A) are responsible for energy production, vacuoles (B) store materials, and ribosomes (D) are involved in protein synthesis. The cell membrane best fits the description of being largely protective.

Correct Answer: B

Rationale: The correct answer is B: Red blood cells lack nuclei. This is because during their maturation process, red blood cells expel their nuclei to make room for hemoglobin, allowing them to carry oxygen efficiently. Nerve cells (A), liver cells (C), and connective tissue cells (D) all have nuclei because they require genetic material for various functions such as protein synthesis, regulation, and repair. Red blood cells, lacking nuclei, are specialized for their main function of transporting oxygen throughout the body.

Correct Answer: C

Rationale: The correct answer is C: Glucose. In photosynthesis, glucose is not a reactant but a product synthesized as a result of the process. Water (A), light energy (B), and carbon dioxide (D) are all reactants in photosynthesis. Water is split into oxygen and hydrogen ions, light energy is absorbed by chlorophyll to initiate the process, and carbon dioxide is converted into glucose through a series of biochemical reactions. Therefore, glucose is the only option that is not a reactant in photosynthesis.

Correct Answer: C

Rationale: The correct answer is C: One daughter may have the disease. This is because Duchenne muscular dystrophy is a recessive sex-linked trait carried on the X chromosome. In this scenario, the unaffected father will pass his Y chromosome to his sons, making them unaffected carriers. The mother, being a carrier, has a 50% chance of passing the affected X chromosome to each daughter, resulting in a 50% chance that one daughter may have the disease. The other choices are incorrect because both sons cannot inherit the disease from the mother, and both daughters cannot carry the disease as they would either be unaffected carriers or affected themselves.