Given a scientific question, generate a correct answer to it.

Input: Consider Input: The urea cycle, a set of biochemical reactions that produces urea from ammonium ions to prevent toxicity, occurs to some extent in the kidney, but primarily in what organ?

Output: liver

Input: Consider Input: Inside each lymph node is a honeycomb of connective tissue with spaces filled by what?

Output: white blood cells

Input: Consider Input: Where do you find the greatest biodiversity?
Output: in the tropics