Do ticks actually serve any purpose in the ecosystem?

[RustyPine17]

I've been wondering if these little bloodsuckers do anything beneficial in nature or if they're just here to annoy us. Anyone know what roles they play, if any?

 

[Swamphunter]

Other than annoying every outdoorsman ever, can't think of one reason for their existence.

 

[Jim0001]

They serve the same purpose as flies, leeches, mosquitoes etc.