Final answer:
Farmers have historically used selective breeding to develop multiple crop varieties from a single species, such as Brassica oleracea. Unlike genetic engineering, selective breeding does not involve direct genetic manipulation but relies on choosing and breeding individuals with desired traits.
Step-by-step explanation:
For centuries, farmers have used selective breeding to produce multiple varieties of one crop. The species Brassica oleracea, for example, has been selectively bred to give rise to cabbage, broccoli, brussel sprouts, cauliflower, collard greens, kale, and kohlrabi.
Selective breeding is a traditional practice where humans breed plants or animals with desirable traits to produce offspring that manifest those traits. This process leads to changes in the genetic makeup of a population over time and has a rich history in agricultural practices.
The practice of selective breeding is different from genetic engineering, which involves the direct manipulation of an organism's genes using biotechnology, and hybridization, which refers to the crossing of two different species or varieties to produce a hybrid.
Mutagenesis is another technique where mutation is induced to create genetic variability; however, it is not the method used historically for crop development as described in the question.