Artificial selection: people choose the traits

0:00How did one wild plant become six very different vegetables?

0:05They all come from wild mustard, also called wild cabbage.

0:10Plants differ in their traits, features passed from parents to offspring. These differences are called variation.

0:19In artificial selection, people choose who breeds. Farmers picked the plants with the biggest leaves.

0:27Their offspring inherit the trait, so they have bigger leaves on average.

0:32Repeat this for many generations, and the leaves get bigger and bigger. The result is kale.

0:40Choosing a big terminal bud, the bud at the tip, gave cabbage. Big side buds gave Brussels sprouts.

0:48A thick stem gave kohlrabi, flowers and stems gave broccoli, and flower clusters gave cauliflower.

0:56All six are still one species. People simply chose different traits.

1:02Breeders do not create new genes. They choose from variation that is already there.

1:08Artificial selection works like natural selection, but people do the choosing instead of the environment.

1:15People bred teosinte, a wild grass with a few hard seeds, into corn.

1:22Ancient wolves were bred into dog breeds with many sizes and face shapes.

1:27But this can cause problems: many flat-faced dogs, like pugs, struggle to breathe.

1:35In artificial selection, people choose which individuals breed, so the traits they choose spread.