Well, an endoskeleton is an internal skeleton, like humans have.
Pro: Bones do not get broke as easily, since they are inside of the body. Bones that break also heal more quickly in an endoskeleton, since they have tissue and blood surrounding it and transferring nutrients.
Con: The flesh can get easily damaged. There is no shedding with endoskeletons, so a new skeleton cannot be grown in the event of an injury.
If a portion of the grass was destroyed by wildfire, then the population of bison that feed on the grass will decrease. This is because there would be very little grass left for them to eat, and they don't eat anything else.