What are the characteristics of a living organism?
First of all, you have to note that there is no such thing as a scientific, objective definition of life, and that many scientists disagree on a given definition, and that every definition has it's limits. 

However, the one from wikipedia 


  Since there is no unequivocal definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that exhibits all or most of the following traits:[10][12][13][14][15][16][17]
  
  Homeostasis: regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature
  
  Organization: being structurally composed of one or more cells — the basic units of life
  
  Metabolism: transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
  
  Growth: maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
  
  Adaptation: the ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.
  
  Response to stimuli: a response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.
  
  Reproduction: the ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.


Encyclopedia Britannica 


  
  Metabolism 
  Respiration
  Sensitivity (responding to stimuli like gravity and sunlight) 
  Nutrition 
  Excretion (getting rid of CO2) 
  Growth
  Reproduction
  Homeostasis