microbiology chapter 12 test bank

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the botulinum neurotoxin, which causes paralysis by blocking the release of acetylcholine at neuromuscular junctions. Clostridium perfringens causes gas gangrene, not paralysis. Escherichia coli is associated with gastrointestinal infections, not paralysis. Staphylococcus aureus produces enterotoxins causing food poisoning, not paralysis. Therefore, Clostridium botulinum is the correct choice based on its well-known association with paralysis due to botulinum neurotoxin production.

Correct Answer: C

Rationale: In anaphase, sister chromatids separate and move towards opposite poles of the cell. This is facilitated by the shortening of microtubules attached to the centromeres. Prophase is the phase where chromosomes condense and the nuclear envelope breaks down. Metaphase is when chromosomes align at the metaphase plate. Telophase is when the nuclear envelope reforms and chromosomes decondense. Therefore, anaphase is the correct phase for chromatid separation.

Correct Answer: D

Rationale: The correct answer is D: Intestinal trichomonad. This protozoan matches the description provided, with pyriform shape, twin nuclei, four pairs of flagella, supporting filaments, and a suctorial disc. Lamblia (A) lacks flagella and supporting filaments. Toxoplasma (B) is an intracellular parasite with different morphology. Leishmania (C) belongs to a different class with no flagella or supporting filaments. In summary, the unique combination of features described in the question points to an intestinal trichomonad, making it the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Prions. Prions are infectious proteins that lack nucleic acids, such as DNA or RNA, which are essential components of all other living organisms, including Archaea, Bacteria, and Viruses. Prions are unique in their ability to cause protein misfolding and aggregation in the brain, leading to various neurodegenerative diseases. The other choices (A: Archaea, B: Viruses, D: Bacteria) all contain nucleic acids in the form of DNA or RNA, making them distinct from prions. Therefore, C is the correct answer in this case.

Correct Answer: D

Rationale: The correct answer is D (69%). The UN projects that by 2050, around 69% of the world's population will live in urban areas. This is based on current global urbanization trends and population growth rates. Urban areas are experiencing rapid population growth due to factors like rural-to-urban migration and natural population increase. Choices A, B, and C are incorrect because they underestimate the expected urban population growth by 2050. A (35%), B (56%), and C (60%) are too low compared to the projected 69%. Urbanization is a significant global trend, and it is essential to consider the implications of this shift for sustainability, infrastructure development, and resource allocation.