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: B

Rationale: The correct answer is B: Calvin cycle. This process occurs in the stroma of chloroplasts and is responsible for converting carbon dioxide into glucose using ATP and NADPH generated in the light-dependent reactions. Photosynthesis (A) is the overall process, including both light-dependent and light-independent reactions. Germination (C) refers to the process of a seed sprouting into a plant, not the light-independent reaction. The phosphorus cycle (D) is a biogeochemical cycle unrelated to photosynthesis.

Correct Answer: A

Rationale: The correct answer is A: transcription. Transcription is the process where RNA is synthesized from a DNA template by RNA polymerase. It involves the synthesis of mRNA, tRNA, or rRNA. During transcription, the DNA double helix is unwound, and RNA polymerase reads the DNA sequence and creates a complementary RNA strand. This process occurs in the nucleus in eukaryotic cells and in the cytoplasm in prokaryotic cells. Choice B, synthesis, is a general term that does not specifically refer to the process of RNA synthesis from DNA. Choice C, translation, is the process where mRNA is used to build a polypeptide chain at the ribosome, not the synthesis of RNA from DNA. Choice D, replication, is the process of copying DNA to produce an identical copy of the original DNA molecule, not the synthesis of RNA from DNA.

Correct Answer: A

Rationale: Condensation is the process in which water vapor cools down and transforms into liquid water. This occurs when the temperature of the air decreases, causing the water vapor to lose energy and condense into liquid droplets. Sublimation is the direct transition from solid to gas phase, not liquid. Precipitation is the process of water falling from the sky in various forms, such as rain or snow, but it does not specifically refer to the transformation of water vapor to liquid. Absorption involves one substance taking in another substance, which is not the process of water vapor becoming liquid water. Therefore, the correct answer is A: condensation.

Correct Answer: C

Rationale: The correct answer is C: Capillaries. Capillaries are found in both open and closed circulatory systems as they are the smallest blood vessels where nutrient and gas exchange occurs. In open systems, capillaries allow direct exchange with tissues, while in closed systems, they connect arteries and veins. Arteries (A) are found in closed systems, not open systems. Red blood cells (B) are present in both systems, but this question specifically asks for a structure, not a component. Immune cells (D) are not typically part of the circulatory system.