Simply watch as the creature(Black) consumes a smaller creature(Red). You might even witness the reproduction of the creature if luck shines upon you. The Black Creature may die off from starvation. If you would like to speed things up, you may change the Eaten variable, which is linked to the age of the black creature.
This simulator is supposed to demonstrate, reproduction, and response to stimuli. Double click the green flag to restart this. There are currently only two generations, as Scratch is a bit limited regarding cloning objects.