Answer:
"Yes" The streak plate method is very effective in diluting the population size in all 4 plates.
Explanation:
The streak plate method is effective because it is one among the rapid isolation method which further allows for easy observation of the bacteria. This method is also being used for getting the color of the certain substances. Its main principle is to isolate the specific bacteria from the sample of various microbes. It dilutes the microbes number and often reduces their density. It is useful in separation of organisms from the group. These are isolated in the agar plate.
I would say immigration only.
emigration would theoretically reduce the genetic variation as unique individuals leave, but immigration would bring unique traits into circulation in an ecosystem.
I'm not super great at biogy tho so this might not be right... :)
Bacterial pathogen can multiply quickly within a small space