I'm so confused help!!! (Will give brainliest)
A population is composed of bacteria that are very sensitive to light. They live in a lake that is in a cave so they flourish. Slowly, however, a hole begins to erode in the cave's roof. As the days pass, light begins to fliter in and the cave starts to be dimly lit. The bacteria begin to die. While the erosion is taking place, however two individual bacteria in the soil above ground fall into the lake. These bacteria cannot survive in the dimness of the poorly-lit cave, so they die immediately. Days later, the hole has opened up so that light floods the cavern. Nevertheless, the bacteria that were once dying are flourishing, with a population larger than they had before the erosion. Explain how this could have happend. There are 2 successive things that must have happened to cause this. What were they.