Living beings have 7 main characteristics:
1. They are composed of cells, which can be single-celled or multicellular.
2. They have a chemical composition and are highly organized from primary bioelements like carbon, hydrogen, nitrogen, and oxygen.
3. Living things use energy, either producing their own through photosynthesis (autotrophs) or consuming organic molecules (heterotrophs).
This summarizes the key points about the characteristics of living beings according to the document.