Final answer:
A first order system has no tributaries and flows into a second order stream.
Step-by-step explanation:
A first order system refers to a stream or river that has no tributaries. It is the smallest and lowest order within a watershed. These first order streams flow directly into the second order streams, which are formed when two first order streams meet.
For example, imagine a large river that flows into the ocean. The smaller streams that flow directly into this river without any other streams joining them are considered first order streams. When two first order streams merge, they form a second order stream.