Which animal introduced by european traders changed the lifestyles of american indians living on the great plains?

horses

Explanation:

European conquerors came with the horse , disrupting the way American Indians lived, since they came to adapt the horse as a companion. With time they became fierce horsemem and hunt other animals like the bisons also becoming nomads as herds of animals moved accross large distances.

The introduction of the horse , made Great Plains habitable, since horses made integration possible sedentary and nomadic lifestyle could coexist.

The Spanish were the first to come with their horses, namely the Conquistadores horsemen with armour. The agriculture and hunting between native americans practices were also shaped by the conditions that their encounters had.

Horses became also used in battle for both sides as many of the early alliances with the Indias were soon disbandled.

b)

it created free trade throughout the colonial territories.