What are elements of the various degrees of homicide?

This is a very involved question and far to lengthy to answer here.  So what I have done is to provide a link to the various homicide statutes for your review:

http://www.flsenate.gov/Statutes/index.cfm?App_mode=Display_Statute&URL=Ch0782/titl0782.htm&StatuteYear=2008&Title=%2D%3E2008%2D%3EChapter%20782

These offenses are defined under Chapter 782 of the Florida Code.  I'm not a Florida lawyer, and a full explanation of all of the homicide offenses would basically have to repeat the statute, because there are a lot of alternatives.

My research suggests the following summary.  Murder is either a premeditated, intended killing, or a killing caused by a person while committing any of a number of specific other felonies, such as aggravated child abuse, arson, burglary, some drug offenses, and forcibly resisting a police officer, to name just a few.  Second degree murder is either a killing due to recklessly dangerous acts with a "depraved mind," or the killing of a person during the course of one of those same felonies, but by someone else participating in the felony -- if Alex and Bob are robbing a house, and Alex kills someone while doing it, Alex is guilty of murder, Bob is guilty of second degree murder.  Third degree murder is the unintended killing of a person while committing any felony other than those on the list for the higher degree crimes.  Manslaughter is any other unintended killing that happens as a result of other illegal acts or "culpable negligence", and it is aggravated manslaughter if the victim is a child, elderly person, or an on-duty police officer or other emergency emergency worker.