Two pure lines of four-o'clock plants, one with red flowers and the other with white flowers, are crossed. The F1 progeny all are pink. When these are selfed, the F2 progeny are 25 percent red flowers, 50 percent pink flowers, and 25 percent white flowers. This is an example of.

Which of the following observation darwin shape his concept of descent with modification? a) species diversity declines farther from the equator. b) fewer species live on islands than on the nearest continents. c) birds live on islands located farther from the mainland than the bird's maximum nonstop flight distance. d) south american temperate plants are more similar to the tropical plants of south america than to the temperate plants of europe. e) earthquakes reshape life by causing mass extinctions.