Laboratory 3 Natural Selection

Lab 3: Flower Evolution

By Melissa Deadmond, Ph.D.

Introduction: In this activity you will explore one of the major driving forces behind evolution, natural selection. At the genetic level, evolution is a change in the frequency of alleles, or alternative gene sequences, in a population over time. Alleles are either selected for or against in a given environment. Alleles are selected against when an individual dies and fails to pass on alleles to the next generation through reproduction. Alleles are selected for when they code for a characteristic that helps an individual to better survive in a given environment. Those surviving individuals then have a greater opportunity of reproducing and passing ontheiralleles to the next generation. Thus, allele frequencies in a population can change from one generation to the next.

You will investigate natural selection in a small population of red, pink, or white wild flowers. The hypothesis is that natural selection impacts allele frequencies. Alleles for flower color are represented by the red and white beans supplied in your lab materials. The red allele (R) is dominant; the white allele (r) is recessive. Heterozygous individuals (Rr) are pink because there is incomplete dominance observed in our flower population. In a lush meadow of colorful flowers and shrubs, the white flowers actually stand out and have a greater opportunity of being picked.