What living things share

A short list of common features.

The definition

Living things are made of cells, use energy, respond to their surroundings, grow, reproduce and pass on information. Viruses meet some of these and not others, which is why their status is argued about.

All known life uses DNA or RNA and the same genetic code.
That shared code is strong evidence of common ancestry.

Levels of organisation

Molecules build cells, cells build tissues and organs, organisms form populations, and populations form ecosystems. Each level has its own rules that the level below does not obviously predict.