Blog Post #8 by Stephanie Wright

Since the beginning of the school year, my teammates and I have closely observed our own Brassica Oleracea, or broccoli. We’ve even observed other groups’ individual Brassica Oleracea plants including kale, cauliflower, cabbage, and of course, broccoli. Many people think of these vegetables as different vegetables entirely due to their relatively small differentiations in size and color. However, they actually share more than 99% of their DNA with each other.





The most variation (greatest number of different forms) between the plants lies in the leaves. They are all different shapes and sizes. Some were large and flimsy, while others were small and stiff. Some were round, some were ridged; the leaves definitely varied in shape. Not only did the shape of the leaves vary, but so did the size. The size demonstrated the greatest range of variation as the average length of the leaves ranged from 12cm to nearly 20cm.








My group members and I measured different leaves and above are the results. Below you will find images of different leaves exhibiting different sizes.








As you can see, the length of this broccoli leaf is 17cm. This is a fairly “normal” size, since the average was 17.67cm.





The same broccoli leaf is 8cm wide which is also the average width for a broccoli leaf.








This image shows the length of a kale leaf. It is 15cm long and the average length of a kale leaf is 13.67cm.








The same kale leaf is about 8cm wide, relatively small compared to the average width of 9.33cm.








This displays the length of a cabbage leaf. The average length is 12.33cm.








This is the same cabbage leaf. Its average width is 9.67cm.








Above and below show a cauliflower leaf. The average length is over 19cm and the average width is 15cm. This means the cauliflower leaves are the biggest overall.








While closely studying the Brassica Oleracea, it became evident that there was a great amount of variability (not in a fixed pattern) amongst the organisms; the measurements show just this. I believe this variability is due to multiple things from artificial selection to natural selection and adaptations. Artificial selection is the name for the process in which humans choose specific (almost always beneficial) traits and develop organisms with said traits. Artificial and natural selection are similar, with the difference being that artificial selection is a result of humans being in control of what traits are passed down, not mother nature. Humans can control this through selective breeding. Selective breeding is the process in which humans breed two individuals of the same organism who both possess “good” traits so their offspring (and their offspring’s offspring and so on) can inherit desirable and/or beneficial genes. The passing of traits from parent to offspring is known as descent with modification. Selective breeding contributes to the variability shown in the Brassica Oleracea plants because its diverse forms are likely a result of farmers choosing specific plants to breed to ultimately create different offspring. Natural variations often come as a result of adaptations. For instance, cauliflower leaves look similar to broccoli leaves, even though they are far bigger (and the largest leaves of the four variations of Brassica Oleracea in our garden). The large leaves could be a result of adaptations. Broccoli plants could have been growing among many other plants and competing for sunlight. Consequently, the broccoli could have adapted over time to grow bigger leaves to capture more sunlight than its competitors. Over many generations, the broccoli would become more and more of its own plant, ultimately creating cauliflower. Another way nature can create variety is through mutations. Changes in DNA, mutations, often affect phenotypes. Some mutations are harmful, and some are beneficial. Some have no effect on organisms. Mutations contribute to the variability of Brassica Oleracea plants. Both mother nature and humans have caused the variability of the Brassica Oleracea plants.





While the plants have some differing traits, they still share 99% of their DNA with each other. This clearly means they are overall very similar. I found the most similar part to be the flowers. Across the board, the flowers were bright yellow, grew at the end of the stem, had about the same number of petals, and were similar in size and shape. They look nearly identical at first glance. Since the variations of Brassica Oleracea can reproduce, it would make sense for the flowers to be the most similar. The flowers have all the reproductive parts of the flower, which is necessary to reproduce.





Below are images of the flowers of the broccoli, kale, cabbage, and cauliflower which clearly display the commonalities between the four.





























In order for breeders to significantly alter the flowers of the plants, they would first have to identify the exact part of the flower they wish to change. One way to change the specific part would be to find individual plants that have the desired phenotype and grow them near each other (so they can reproduce through pollination). Over several generations, the plants would begin to show the desired phenotype. Another way to change parts of the flower would force it to adapt. This could mean planting it in an atypical location or introducing a new organism to its existing environment. The flower would be forced to adapt or die as a result.