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NAME: DATE: PER: Agricultural Examples of Artificial Selection Corn The history of modern-day maize begins at the dawn of human agriculture, about 10,000 years ago. Ancient farmers in what is now Mexico took the first steps in domesticating maize when they simply chose which kernels (seeds) to plant. These farmers noticed that not all plants were the same. Some plants may have grown larger than others, or maybe some kernels tasted better or were easier to grind. The farmers saved kernels from plants with desirable characteristics and planted them for the next season's harvest. This process is known as selective breeding, or artificial selection. Maize cobs became larger over time, with more rows of kernels, eventually taking on the form of modern maize. The identity of maize's wild ancestor remained a mystery for many decades. While other grains such as wheat and rice have obvious wild relatives, there is no wild plant that looks like maize, with soft, starchy kernels arranged along a cob. Through the study of genetics, we know today that corn's wild ancestor is a grass called teosinte. Teosinte doesn't look much like maize, especially when you compare its kernels to those of corn. But at the DNA level, the two are surprisingly alike. They have the same number of chromosomes and a remarkably similar arrangement of genes. In fact, only about 5 genes are responsible for the most-notable differences between teosinte and a primitive strain of maize. Bananas Around seven thousand years ago, the first bananas were discovered. In the wild, bananas were not easy to eat. They probably had to be peeled using sharp rocks, and whoever was eating them would have had to constantly spit out big seeds. However, not all the bananas were exactly the same as each other. Just like humans, some bananas were thinner than the others, some had different skin colours, some were especially seedy and some were sweeter than the rest. Humans didn’t fail to notice this biodiversity in the banana trees. They collected the bananas with the most desirable qualities they could find, and bred them. They found bananas with the smallest seeds, bananas with the thinnest skin, bananas that were longer than the others, and used them to plant new banana trees. As the artificial selection process was repeated over thousands of years, we finally arrived at today’s model. Modern bananas have the right thickness to fit snugly in your hand. The surface of a banana is anti-slip, making it easy to hold and to eat. There is a finger-sized tab on the top of every banana. All you have to do is to pull it lightly, and the skin peels away from the edible fruit inside. NAME: DATE: PER: Artificial Selection 101 Artificial selection is a process in which humans select animals and plants based on certain traits, to ensure that future generations will inherit those traits. Essentially, humans alter the evolution of organisms for their own benefit, rather than allowing nature to select the traits that will increase the fitness of the organism over time. Limitations: 1. Essentially removes variation in a population. (Diluting the gene pool of species.) 2. Selectively bred organisms can be especially susceptible to diseases or changes in the environment that would not be a problem for a natural population. 3. Unable to control genes inherited by offspring, so this trial and error method is a slow process that involves breeding over a few generations. 4. May create infertile hybrids. Advantages: 1. Economically beneficial because the process itself is almost free, especially if one is in the agriculture business. 2. Able to produce crops with higher yield, shorter harvest time, higher resistance to pest and diseases and better taste in an inefficient yet somewhat natural way. 3. No human safety issues from consuming artificially selected plants, such as those brought about by genetic engineering. 4. Most people are comfortable with selective breeding of plants and animals as it has been practiced for centuries, while many people still worry about the safety of genetic modification.