The kidneys are bean-shaped organs responsible for filtering waste products from the blood. What is the main nitrogenous waste product the kidneys eliminate?

Correct Answer: C

Rationale: The correct answer is C, urea. Urea is the main nitrogenous waste product eliminated by the kidneys. It is produced in the liver from protein metabolism and excreted in urine. Carbon dioxide is eliminated through the lungs as a waste product of cellular respiration and not by the kidneys. Ammonia, a toxic waste product, is converted to urea in the liver before being excreted by the kidneys. Glucose is a sugar that is reabsorbed by the kidneys and not excreted as waste.

Correct Answer: D

Rationale: B cells are responsible for producing antibodies as part of the adaptive immune response. When activated by a specific antigen, B cells differentiate into plasma cells that secrete antibodies to target and neutralize pathogens. Natural killer cells are primarily involved in killing infected or cancerous cells, phagocytes engulf pathogens, and helper T cells assist in activating other immune cells. Therefore, the correct answer is B cells because they play a crucial role in antibody production, a key component of the adaptive immune response.

Correct Answer: D

Rationale: The Gram stain is a differential staining technique that categorizes bacteria into two groups based on their cell wall composition: Gram-positive and Gram-negative. Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet stain used in the Gram staining procedure. Consequently, Gram-positive bacteria appear purple under the microscope after staining. On the other hand, Gram-negative bacteria possess a thinner peptidoglycan layer and an outer membrane that can be penetrated by the counterstain safranin, leading them to appear pink or red. Blue is not typically used to describe the color of bacteria in a Gram stain, making it an incorrect choice.

Correct Answer: B

Rationale: Aseptic meningitis is typically caused by viral infections, such as enteroviruses (e.g., coxsackievirus, echovirus), herpes simplex virus, varicella-zoster virus, and others. These viruses can infect the meninges, leading to inflammation and symptoms of meningitis without the presence of bacteria. While bacterial meningitis is a serious and life-threatening condition, aseptic meningitis caused by viruses is usually less severe and has a better prognosis. Fungi and parasites are less common causes of meningitis compared to bacteria and viruses.

Correct Answer: C

Rationale: A) Acclimatization refers to the short-term physiological adjustments an individual organism makes in response to changes in its environment. This process is reversible and does not involve inherited traits. B) Behavioral ecology is the study of how behavior contributes to an organism's survival and reproduction in its environment. While behavior can be influenced by natural selection, it is not the process by which an organism adapts through inherited traits. C) Natural selection is the process by which organisms with advantageous traits for their environment are more likely to survive, reproduce, and pass on those traits to their offspring. Over time, this leads to the adaptation of populations to their environments. D) Niche partitioning is the process by which species divide resources to reduce competition within an ecosystem. While this can influence the evolution of species, it is not the process by which an organism adapts through inherited traits.