Firstly- Welcome to FNZAS!!! Secondly- what level is this for??? I could recommend a heap of sources but if it is for a NCEA level 3 essay or something they might be a little more info than you need...
Simply though- (If you haven't got this far already)
1. Fanning is a form of Parental care in Fish. They fan their eggs to keep fresh water flowing past them, Thus removing detritus and keeping fungus and bacteria from settling on, and destroying the egg.
2. The fish which fans its eggs is more likely to have a greater hatch-rate. It pretty much goes from there
3. ??? I don't get that question. I suppose it is talking about Natural selection. Essentially, with Natural selection, the most "fit" organisms are likely to have more offspring. By fit i am not referring to athleticism, but rather reproductive success. In modern human society, what is happening is that this is being distorted. For example, a Woman of higher intellect is likely to have fewer babies than a women of lower intellect, simply because their professional life gets in the way of their childbearing "potential". There are many more examples of this.