November 2- Speciation

 3 Questions Regarding Speciation:

1. One thing from an earlier video was that, a far off ancestor can tell if something is related to them and then will choose not to mate. HOW??? That just seems incredibly hard.

2. I get the technical differences between natural selection and sexual selection. But then again, they kind of blur into each other. What is the determining factor between them?

3. Many times, do species just try to interbreed and then do not have a successful outcome?