Hardy-Weinberg Principle HELP!!!

[artelart]

Hello,
I am having trouble with understanding HW principle.
The questions are:

1) How can the HWP be used to determine whether population is evolving?
2) Identify a particular environmental change and describe how it might alter allelic frequencies in the population. Which condition of the HWP would not be met?

Thanks in advance!

[JackBean]

2) presence/absence of malaria and reciprocal absence/presence of the "special" hemoglobin

[Darby]

It tells you what conditions are needed for NO evolutionary changes...