I got this from this web site: (I have shortened it a bit for space)
http://www.physicalgeography.net/fundamentals/9a.html)
There are four main types of life.
Bacteria, Eukaryota (protozoa, fungi, animals, plants), Viruses and Archaea (similar to bacteria but can live in extremely hostile environments such as volcanic vents and are single celled).
The four main types of biological entities described above share some unique characteristics that can allow us to distinguish them from non-living things. These characteristics are:
(1). Organisms tend to be complex.
(2). Living things have the ability to take energy from their environment and change it from one form to another or the ability to metabolize.
(3). Organisms tend to be homeostatic. In other words, they regulate their bodies and other internal structures to certain normal parameters.
(4). Living creatures respond to stimuli.
(5). Living things reproduce themselves.
(6). Organisms tend to grow and develop.
(7). Life adapts and evolves in step with external changes in the environment through mutation and natural selection.