Having researched adaptations S4 went on to look at the natural selection. They drew their own mouse then choose various features for their mouse (hair length, teeth numbers, coat colour etc).
They then went on to see if the features they had selected would ensure the survival of their mouse. All of them survived except poor Aimee's mouse as she had chosen to put the eyes of her mouse in a central position - poor thing it couldn't spot predators coming at it form the side and was eaten. That's survival of the fittest for you!