What comes after class in the classification system?

Correct Answer: B

Rationale: The correct answer is B: Phylum. After class in the classification system comes phylum. The classification system starts with the broadest category, which is the kingdom, followed by phylum, class, order, family, genus, and species. Phylum is a higher level of classification than class, so it comes next in the hierarchy. Domain is a higher level than kingdom, and order is a lower level of classification than class. Therefore, the correct sequence is kingdom, phylum, class, order.

Correct Answer: B

Rationale: The correct answer is B: Escherichia coli. E. coli is a common bacterium found in the gastrointestinal tract and is a leading cause of UTIs. It has specific virulence factors that enable it to adhere to and infect the urinary tract. Salmonella enterica causes food poisoning, Vibrio cholerae causes cholera, and Streptococcus pyogenes causes strep throat and skin infections, not UTIs. Therefore, B is the correct answer as it is the only bacterium known for causing UTIs.

Correct Answer: D

Rationale: The correct answer is D, Salmonella typhi, because it is a motile bacterium due to possessing flagella that aid in movement. Bacillus anthracis (A) is non-motile, Klebsiella pneumoniae (B) lacks flagella for motility, and Shigella flexneri (C) is non-motile as well. Salmonella typhi (D) is known for its flagella-driven motility, allowing it to move and spread within its host and environment. Flagella are essential for bacterial motility, enabling them to navigate and colonize different environments efficiently.

Correct Answer: A

Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, which can be transmitted to humans through contact with infected cat feces. During pregnancy, Toxoplasma infection can result in severe birth defects such as microcephaly and mental retardation in the child. In this case, the presence of a cat in the family and the child's abnormalities suggest a possible link to Toxoplasmosis. Other choices are incorrect because: B: Leishmaniasis is a parasitic disease transmitted by sandflies and does not typically cause the specific birth defects mentioned in the scenario. C: Dysentery is a bacterial infection that primarily affects the intestines and does not cause the neurological abnormalities described. D: Balantidiasis is a parasitic infection caused by Balantidium coli, a ciliated protozoan, but it is not associated with

Correct Answer: C

Rationale: The correct answer is C because diphtheria exotoxin is absorbed into the underlying healthy tissues and spreads throughout the body. This is due to the toxin's ability to enter the bloodstream and target various organs, causing systemic effects. Choice A is incorrect as the toxin does not stay localized at the site of infection. Choice B is incorrect as diphtheria exotoxin does not directly affect neuro-muscular transmission. Choice D is also incorrect as the toxin does spread throughout the body.