How do mutations increase the genetic variation within a species? Why doesn't a mutation ALWAYS affect the organism's phenotype?

What is the purpose behind gene expression and regulation?

(Please answer I’ve been stuck for like a week) (it’s giving me a headache)

Expression of Genes. For a cell to function properly, necessary proteins must be synthesized at the proper time. All cells control or regulate the synthesis of proteins from information encoded in their DNA. The process of turning on a gene to produce RNA and protein is called gene expression.

Explanation:

a=c and then d= c because of the band so you get ac/dc and you add them together you get sound waves

if the hares very faster than they are now, and thus the lynx's hunting success rate drops because it will be harder to catch them, the rate that will change will be the pray-rate. the pray-rate will change because more hares will be able to survive, thus more individuals for reproduction, so the end result will be increasing population of hares.

the predator-rate will remain pretty much the same because there will be more than enough pray, but the hunting success rate is stagnant.