Final answer:
Reproduction is the fundamental characteristic of life, as it ensures the continuity of species over generations.
Step-by-step explanation:
The fundamental characteristic of life is reproduction. All living organisms share several key characteristics such as order, sensitivity to the environment, growth, and adaptation, but reproduction is essential for the perpetuation of species.
While all living things also maintain homeostasis, have complex chemistry, and are built of cells, it is their ability to reproduce, which ensures that life continues into the next generation.