Biology

Acclimatization refers to the gradual physiological adjustment of an organism to changes in its environment, such as temperature or altitude, over time. This distinguishes it from terms like selection or quarantine, which have different meanings.

The iris contains the pigment that determines the color of a person's eyes. The amount and type of pigment in the iris control eye color, making option B correct.

Vitamin K is synthesized by intestinal bacteria in the human gut, making option D correct. Vitamins B1, B12, and E are not synthesized by gut bacteria.

The pancreas secretes insulin, a hormone that regulates blood sugar levels. It does not secrete Vitamin A or bile juice, which are produced by other organs.

In eye donation, the cornea is the part of the donor's eye that is commonly utilized for transplantation to restore vision in recipients with corneal blindness. Other parts like the iris, lens, and retina are generally not used in standard eye donation procedures.

During a total solar eclipse, sunlight is blocked, reducing light intensity drastically. Since photosynthesis depends on light, its rate decreases during the eclipse.

Insulin was discovered by Sir Frederick Grant Banting and Charles Herbert Best in 1921. Banting is often credited as the primary discoverer, which is why option C is correct. Leonard Thompson was the first patient to receive insulin treatment, and Macleod was a supervisor and co-recipient of the Nobel Prize.

The human heart beats about 100,000 times per day. Each heartbeat causes the four heart valves (mitral, tricuspid, aortic, and pulmonary) to open and close once. Since there are four valves, the total number of valve openings and closings per day is approximately 400,000. The closest option to this is 200,000 (option D), which is a reasonable approximation given the options provided, although the actual total is higher. The question likely refers to the total number of times all valves open and close combined, not just a single valve.

The AIDS virus, known as HIV, is a single-stranded RNA virus. It belongs to the retrovirus family, which uses RNA as its genetic material.

Kidney stones are primarily composed of calcium oxalate, which is the most common constituent of these stones formed in the human kidney.