HESI A2 Biology Practice Test

Correct Answer: D

Rationale: Step-by-step rationale: 1. Diploid organisms can be multicellular or unicellular, so A is not universally true. 2. Diploid cells can be somatic or germ cells, so B is not always true. 3. Diploid cells always have two sets of homologous chromosomes, making C true. 4. Since C is true and A and B are not always true, the correct answer is D.

Correct Answer: D

Rationale: The correct answer is D because it follows the structure of a hypothesis: it states a relationship between two variables (exposure to red light and plant growth) that can be tested. It is specific, testable, and predicts an outcome. Choice A is a general statement, not a testable hypothesis. Choice B is subjective and not testable. Choice C lacks specificity and does not clearly define the relationship being tested.

Correct Answer: D

Rationale: The plasma membrane is a phospholipid bilayer, meaning it consists of two layers of phospholipid molecules. This arrangement forms a barrier that separates the cell from its external environment. The hydrophobic tails of the phospholipids face inward, while the hydrophilic heads face outward. This structure allows the membrane to control the movement of substances in and out of the cell. Choices A and B are incorrect as the membrane is not solely made of proteins. Choice C is incorrect as the membrane consists of a double layer of phospholipids, not a single layer.

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: D

Rationale: The correct answer is D: Biomes. Biomes are large geographical areas characterized by specific climate, vegetation, and animal life. Tundra, savannas, grasslands, deserts, and rainforests are all examples of biomes. They are classified based on factors like temperature, precipitation, and flora/fauna. Biomasses (A) refer to the total mass of living organisms in a given area. Biospheres (B) are the regions of the Earth where life exists. Biodiversity (C) refers to the variety and variability of life forms in a specific habitat, not the specific types of habitats themselves.