Taxonomy and allele.

[RL543]

Hello, I would like to know the answers to these 2 questions and the basics behind them.
1) A properity that has slowly changed is useful in determing...? Is it a family? A class?
2)In chickens the allele of FB is responsible for black feathers, FW for white feathers, and if there's a hetrozygote situation ,then the feathers are blue.
In a hybrid of hetrozygotes with hetrozygotes 78 black-feathered chickens were born, 206 blue and 116 white. What is the allele frequency in a population that's in a balance?
Thanks.Have a good day.