HESI A2 Biology Practice Test

Correct Answer: C

Rationale: The correct answer is C because plant cells have a rigid cell wall that prevents them from forming a contractile ring during cell division. The cell wall provides structural support, making it challenging for plant cells to constrict and pinch apart like animal cells. This rigidity limits the flexibility needed for the contractile ring to form and function effectively. Plant cells primarily rely on other mechanisms such as cell plate formation for division. Choices A and B are incorrect as they do not address the specific structural difference between plant and animal cells. Choice D is incorrect as it does not provide any relevant information on the topic.

Correct Answer: B

Rationale: To focus an image using a compound microscope, adjusting the fine adjustment is correct as it allows for precise focusing when switching magnifications. Coarse adjustment is only used initially to bring the specimen into view, while the stage adjustment is used to center the specimen. Therefore, B is correct as it ensures clear and sharp image focus without unnecessary readjustments. Choices A and C are incorrect as they do not address the specific need for precise focusing when changing magnifications, leading to potential blurriness or loss of focus in the image.

Correct Answer: C

Rationale: The correct answer is C: Prometaphase. This phase of mitosis is characterized by the disintegration of the nuclear envelope. During prometaphase, the breakdown of the nuclear envelope allows the spindle fibers to access the chromosomes. This is crucial for the proper alignment and separation of the chromosomes during mitosis. In prophase (choice A), the nuclear envelope starts to break down but is not fully disintegrated. In metaphase (choice D), the nuclear envelope is already broken down, and the chromosomes are aligned at the metaphase plate. Therefore, prometaphase is the specific phase where the nuclear envelope completely disintegrates, making it the correct answer.

Correct Answer: A

Rationale: The correct answer is A: The nucleus. DNA is stored in the nucleus of a cell because it contains the genetic material that carries instructions for the cell's functions. The nucleus is specifically designed to protect and regulate access to the DNA. Ribosomes (B) are responsible for protein synthesis, not DNA storage. Endoplasmic reticulum (C) is involved in protein and lipid synthesis, but not DNA storage. Mitochondria (D) have their own DNA, but the majority of the cell's DNA is stored in the nucleus.

Correct Answer: D

Rationale: The correct answer is D: species. Within the biological hierarchical system, species is the least inclusive category. A species consists of organisms that can interbreed and produce fertile offspring. Moving up the hierarchy, species are grouped into genera, then families, orders, classes, phyla, and finally kingdoms. Phylum (A), order (B), and kingdom (C) are all more inclusive categories than species. Phylum includes multiple classes, order includes multiple families, and kingdom includes multiple phyla. Therefore, species is the least inclusive category within this system.