Are mosquitoes relevant?

Can someone tell me why Mosquitoes were created. What purpose they serve to man and animal. If evolution is true, how did mosquitoes evolve? What did they evolve from? Are they eventually going to grow bigger and bigger and bigger? That's a scary thought. I have over a thousand questions on this topic, but I guess it's waste of time talking about it. I will let it go for now, just for now, but I will continue to trouble my head in my silent moment about it. You can contribute to this topic by telling us other things that were created you find irrelevant to our existence.