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

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?
liver

Would you find cells that contain a cell wall, a large central vacuole, and plastids in plant or animal cells?
plant cells

The average number of individuals per unit of area or volume is referred to as a population's what?

density

