10 most extreme places on Earth. A unicellular organism is any life form that consists of just a single cell. This group includes most life on Earth, with bacteria serving as the majority. The main groups of single celled life are bacteria, archaea (both prokaryotes), and the eukaryota (eukaryotes).
A hero (masculine) or heroine (feminine) is a person or main character of a literary work who, in the face of danger, combats adversity through impressive feats of ingenuity, bravery or strength, often sacrificing his or her own personal concerns for some greater good.
The word hero or heroine, in modern times, is sometimes used to describe the protagonist or the love interest of a story, a usage which can conflict with the superhuman expectations of heroism. A classic example is Anna Karenina, the lead character in the novel of the same title by Leo Tolstoy.