a biologist wants to estimate the size of a population of turtles in a large lake. she captures 100 turtles on her first visit to the lake, and marks their backs with paint. a week later she returns to the lake and captures 200 turtles. 20 of these 200 turtles have paint on their backs, indicating that they are recaptured animals. what does she estimate is the population size of turtles in this lake? a