Final answer:
The urea hydrolysis medium is a differential medium because it differentiates between bacteria based on their ability to produce the enzyme urease. It is not selective as it doesn't inhibit the growth of any specific bacterial group. The presence of urease is indicated by a color change in the pH indicator phenol red within the medium.
Step-by-step explanation:
The question regarding urea hydrolysis and whether the medium used is selective, differential, or both, pertains to microbiology, a sub-discipline of biology. The urea hydrolysis test is able to distinguish between different bacteria based on their ability to produce the enzyme urease, which hydrolyzes urea into ammonia and carbon dioxide, thereby increasing the pH of the medium. This change in pH is indicated by a color change of the pH indicator phenol red. When urease-positive bacteria grow in the medium, they produce ammonia rapidly, causing the pH to increase and the phenol red to turn from yellow to pink or fuchsia, indicating a basic environment. Therefore, this medium is differential because it allows one to visually differentiate between bacteria that produce urease rapidly and those that do not, based on the color change. This medium is not inherently selective because it does not inhibit the growth of any particular group of bacteria over another.