If this was the essay prompt, I would outline it as follows (please note each section is a section not a paragraph). You will have to research each of these ideas on your own; while I have given some examples, you should use your own based on your reading experiences.
Introduction -- definition of literature and English literature
Body 1 -- History -- discuss each time historically and how the history affected the literature of the period.
(think of literary movements as well, such as existentialism, romance, etc.)
- oral tradition and its impact
- medieval literature -- usually religious, Arthurian, or courtly romance. ie. Canterbury tales
- Elizabethan -- Shakespeare, Christopher Marlowe
- renaissance -- printing press, John Donne, John Milton
- 18th century -- essays, rise of the novel,
- 19th century -- addition of the American novel (Huck Finn, etc.)
- 20th century -- impact of WWI, Depression, WWII (lost generation, beat generation, etc.) -- Sylvia Plath, Hemingway, Jack Kerouac, Lord of the Flies, etc. The dystopian novel,
Body 2 -- common themes -- these are topics as opposed to actual themes. The author's write give their particular bent on the topics as their individual themes. You should compare and contrast some major authors and their takes on some of these. Remember, the themes should be timeless.
- Freedom / slavery -- this does include mental as well as physical
- the inevitability of death.
- good and evil -- Macbeth, Lord of the Flies, Dr. Faust, etc.
- The effects of society on the individual
- Human versus nature
- suffering and redemption -- Kite Runner; Cry, The Beloved Country
- fate vs. predestination
- the power (or lack of) of the individual
Body 3 -- the cannon and how it is changing
- some would argue that English literature should be limited to British literature, some say anything written in English, but it is also changing to accept literary works that may have originally been written in other languages.
- As the world changes and our understanding of the world changes, the cannon may change as well.
conclusion -- Overall, what makes English Literature English Literature? What changes do you see coming in the future? What do you perceive is the most important element in English Literature?