Disruptive selection.
Disruptive selection eliminates phenotypes near the average and favors the extreme phenotypes, resulting in increased genetic variation in a population.
Your question is rather unclear but from what I can tell either there were not an even amount of Petri dishes or some of them were left open while others were not.
Electric Power
Because Eletric Things Dont Need Oil
Electricity Is Made Up Of WIres Which Is How We Get Our Electricity
The cell process is being described is cytokinesis.
