Answer:
Eckels steps on the butterfly in the short story, while his partner in the film, Middleton, was the one who stepped on it (Middleton was not in the short story) The short story has the safari team go back in time to shoot a Tyrannosaurus Rex, while the film has the safari team go back to kill an Allosaurus (while the film had terrible graphics, it would not have mattered which type of dinosaur was used)
Explanation:
