I changed the first sentence from:

Sexual ethics or sex ethics (also called sexual morality) is the study of human sexuality and the expression of human sexual behavior.

This doesn't seem quite right, because sexual ethics is not merely the study of human sexuality and sexual behavior, but rather, the ethical investigation of sexual behavior. Changed to:

Sexual ethics (also called sex ethics or sexual morality) is the branch of ethics and applied ethics concerned with ethical questions related to human sexual behavior.