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.
Answer:
C
Explanation:
Keystone species is the sea otter. Sea otters, playing a critical role in containing the urchin populations, prey on urchins and thus control the numbers of kelp grazers to maintain the forest.
Remember, keystone species is most often a top level predator in an ecosystem.
An example of selective breeding is breeding cattle to produce better meat.
So understanding<span> how the </span><span>DNA </span>molecule behaves inside cells<span> helps explain how genetics works</span><span> at the simplest level. </span>
The energy needed by a system to initiate a process is called as the activation energy. It describes the minimum energy which must be available to a chemical system with potential reactants to result in a chemical reaction. Hope this answers the question.
