Artificial selection

Brassica rapa plants have small, hair-like structures called trichomes on their stems and leaves. The number of trichomes on a plant is genetically determined and can vary widely among individuals.

A group of students grew a population of B. rapa plants, Generation 1, in their classroom and counted the number of trichomes on the first true leaf of each plant (Figure 1).

Next, the students used the Generation 1 plants with the highest number of trichomes as parents for the next generation, Generation 2. The students grew the B. rapa plants of Generation 2 and counted the number of trichomes on the first true leaf of each plant (Figure 2).

Then, the students used the Generation 2 plants with the highest number of trichomes as parents for the third generation, Generation 3.