A major sign of life seen during the reproductive process is that the offspring resemble their parents. The seeds of a petunia plant grow into new petunias, for example, and mice have offspring that look like mice.
This continuity of appearance stems, to a large degree, from the fact that every living organism contains within it a set of coded instructions or blueprints that determine how the organism will grow, what it will look like, how it will behave, where it can live, how long it will live, and, in some cases, how and when it will die.
During reproduction, each individual organism receives a set of these coded instructions from its parent or parents. After copying them, an organism passes a set onto its own offspring in a never ending progression of reception, use, copying and transmission.
In this way, the information needed to grow and produce more individuals is passed on from one generation to the next in a precise and regulated manner that follows certain rules and obeys certain principles. It is inherited.
A combination of the reproductive process and the inheritance of coded instructions provides the continuity and the relative consistency of form and function that each living thing shares with other members of its own kind.
The way in which coded information is passed from one generation to the next is a vital sign of life on earth, and similar types of mechanisms would be expected on any "alien" form of life that may one day be discovered.