HESI A2 Biology Practice Test

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.

Correct Answer: C

Rationale: Anaerobic respiration occurs in bacteria because they live in environments with low oxygen levels. Bacteria adapt to anaerobic conditions by utilizing alternative pathways to generate energy without oxygen. This process allows them to survive and thrive in oxygen-deprived environments. The other choices are incorrect because animals require oxygen for aerobic respiration, plants use sunlight for photosynthesis, and option D is incorrect as bacteria indeed undergo anaerobic respiration in low oxygen environments.

Correct Answer: D

Rationale: The correct answer is D: Plasma membrane. The plasma membrane is the outer boundary of an animal cell that regulates the movement of substances in and out of the cell. It is composed of a phospholipid bilayer with embedded proteins. "Biological membrane" is too broad and vague, not specifying the cell's outer boundary. "Cell coat" refers to the glycocalyx on the cell surface, not the main membrane. "Unit membrane" is a general term for any biological membrane with two lipid layers, not specific to animal cells.

Correct Answer: B

Rationale: Thymine is not present in RNA because thymine is a pyrimidine base found in DNA instead of RNA. RNA contains uracil as its complementary base to adenine, while DNA contains thymine. Adenine, uracil, and cytosine are all present in RNA, making them incorrect choices. Thymine is the only base not present in RNA, making option B the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Prokaryotic cells have a capsule. This is because the capsule is a protective layer outside the cell wall that helps the prokaryotic cell adhere to surfaces and evade the immune system. Prokaryotic cells do not have a nucleus (choice A), membrane-bound organelles (choice C), or the ability to move on their own (choice D). The absence of a nucleus and membrane-bound organelles distinguishes prokaryotic cells from eukaryotic cells. Choice D is incorrect because prokaryotic cells can move using various mechanisms such as flagella or pili.