A way to say that it deals with, or is, sex without saying it. Very useful when a shy or inexperienced person is trying to avoid embarrassment. Can also be used to keep the true meaning of a conversation/question from being realized. Biology in this case means reproduction or sex.
1. "It deals with biology." Spock to Kirk. Spock was not about to say 'sex' to Kirk. He was too embarrassed.
2. "I'm not sure what Paul and Ali (girl) did last night, but I'm sure it dealt with biolody," Joanne said to Virgina.
3. "He asked me to help him with his biology! Little did I know that he didn't mean his homework!" - geeky girl