When something or someone is living they must have certain needs/characteristics in order to be living.  Most living things need: water, food, and oxygen.  Characteristics include: reproduction, death, and growth.  For example, a plant needs nutrients which come from the sun, soil, and water which is considered food and water.  They need oxygen to produce sugar and energy which helps with functions of growth such as photosynthesis.  Plants do die and some plants or weeds reproduce, but not in the way that animals would.  Wind carries seeds from the plant to areas of soil which then grow there so it is not really considered reproduction but is somewhat similar.  In our lab we used 5 different vials and put certain materials/things into the vials.  This was the manipulated variable. Certain amounts of liquid into each vile, some the same amount. there were 3 different liquids: water, salt water, and sugar water.  each table team was given a different liquid, a few had the same liquid.  We let the liquid sit in the vials and over time we recorded the effects on the materials and detemined if they were living or nonliving.  We also determined which materials were affected more in each liquid enviorment.  Certain materials reacted more in one liquid than it would in another.  If the characteristics/needs match what living is then it was considered living.