The second question is far simpler Amberleaf. If you do not have a lot of pH buffering in your water, the ammonia, which is a weak base as ammonium hydroxide, gets processed to eventually become nitrates which occur in many forms including nitric acid. The shift in pH happens because you are removing a weak base and replacing some part of it with a strong acid.
The first question is much harder but one of the theories goes more or less along these lines. A female of any species invests much more of her energy into the reproductive process than a male. Because that is true, the female ends up being the one that selects mating partners, not the male. A female will respond to the good looking males more often than to the drab ones, so the successful males often become more ornate than the females, because they are trying to win in the competition for breeding rights with the females.
