Question

why speed is important for the survival in the grassland for animals that live there?

Answer 1

In a grass land habitat their are no trees and places places for animals to hide. When enemies or predators attack them they have to run fast to reach to the safer place otherwise they will be killed. So in odder to escape from the predators speed is important for survival of animals living in grassland habitat. My 1st answer of the day

Answer 2

speed is an important factor for the survival in the grasslands for animals that live there. animal whether it is predator or prey needs speed. 
prey needs to run fast and think fast to escape from predators. if their speed will be slow, then they won't survive.
predators need to be quick to catch prey. if they'll be slow, then they won't be able to catch prey and they'll die due to hunger or starvation. so speed is necessary for survival of all in grasslands.