Artificial Selection

When you look at a population of animals you may notice some variations or differences between individuals of the same species. Perhaps some are larger than others or there are differences in their coloration. These variations serve as the basis for natural selection where beneficial traits in a population that positively affect survival and reproduction will be preserved. For example, animals that can more easily camouflage with their environment evade predators and pass on their genes more often than those that do not. This camouflage coloration is a phenotype, defined as the visual expression of a trait. A genotype refers to the set of genes responsible for a phenotype. Therefore, due to natural selection certain genotypes are maintained over time, while less favorable variations disappear and this drives the evolution of populations.

We humans have studied this process and taken advantage of naturally occurring variations to purposely evolve plants and animals to farm or keep as companions. This process is known as artificial selection, the propagation and domestication of plants and animals for favorable traits. Let's look at dogs for example. Thousands of years ago, humans started selectively breeding pairs of wolves for traits like docility, protection and hunting prowess along with appearance. We continued this selective breeding over countless generations and this has culminated in scores of modern dog breeds, including the Great Dane and Chihuahua, which in turn are both very different in appearance and character to their ancestor, the wolf.

We have also implemented artificial selection in plants. Brassica oleracea was once a large, leafy plant, but it has been artificially selected in different ways to produce many common vegetables we eat today, including kale, cabbage, cauliflower and even kohlrabi. Another species in the same family, Brassica napus, is commonly known as the oilseed rape plant because of the abundant oil sequestered in its seeds, which are excellent for cooking or fuel production.

In this lab, you will artificially select traits from individual oil seed rape plants to produce two lines displaying different levels of a trait, hairiness.