Reason: The essay test is not objective. Whether you pass or fail the test is largely dependent on the individual reviewing your test.
Paragraph #1: Introduction.
Paragraph #2: First Body Paragraph
Paragraph #3: Second Body Paragraph
Paragraph #4: Third Body Paragraph
Paragraph #5: Conclusion
Sentence #1: introduces the key concept to be discussed in the paragraph.
Sentence #2 to #second Last: explains the key concept further by giving examples etc.
Last Sentence: closing statement giving a mini-summary of the issue discussed in the paragraph.