Abbie Weimer Blog Post #8

A Matter of Selection


In our garden, there are four different plants. There is cabbage, kale, cauliflower, and of course, our plant, broccoli. These plants have many similarities, as they are from the same common ancestor. In fact, these plants share 99% of their DNA. Despite their many similarities, they have some obvious differences my team and I observed. We found that the part of the plant with the most variation is the shape of the leaves. Each type of plant had leaves with different shapes than the rest. The broccoli had dark, cool-green, boat-shaped leaves. The cauliflower had leaves with ruffle-like edges but was flatter than the broccoli and cabbage leaves. This variation had leaves that caved towards the center vein. The kale leaves were even more abnormal looking, and they were ruffed like the cauliflower. However, the sides were not straight. The edge of the leave curved in and out like a rounded spike. The cabbage leaves were the most simple, but also the most different from the rest of the leaves. The cabbage leaves were sturdier and round. The edges didn't have any ruffles or purposeful indentation. The part of the plant that had the greatest range of variation was also the leaf shape, as it went from an oval-shaped cabbage leaf that caved at the middle to a flat kale leaf with parabolic spikes on the edges. We never would have thought plants sharing 99% of their DNA would have so many different characteristics!



Above are the measurements (length and width) and averages of all the plant leaves and flowers


 


Above is the length and width of one of the broccoli leaves. We found the average length to be 17.67cm and the average width as 8cm 


Above is the length and width of one of the kale leaves. The average length is 13.67cm and the average width is 10.33cm




Above is the length of a cauliflower leaf, the average being 19.67cm 
Below is the width of a cauliflower leaf, the average being 15cm 

Above are the cabbage leaf measurements. The average length of the measured cabbage leaves was 12.33cm and the average width was 9.67cm

Over time, most species are forced to adapt to the environment. Sometimes these adaptations don't affect all of the population, however, and this creates natural variation within a species. Natural variation occurs when one species has multiple types of traits within it. Humans, for example, can have different color eyes but are all the same species. This can result in selective breeding, where one variation only breeds with individuals of the same variation. If the variation affects the organisms genes, then decent with modification will occur. This basically means that the traits will be passed on to future generations. Sometimes, however, a mutation will change the variation in the offspring, even though it had been passed down through descent with modification. As we already know, mutations can be both good and bad for a species. With all of these combined things, there are many ways that a species can develop variation.

We found that the least varying parts of the plants were the flowers. We didn't see any flowers on the kale plant, but we discovered places where it looked like flowers had fallen off. This could mean that flowers had once been there, but were not anymore. All of the flowers we found seemed to be almost identical. You can see the bright yellow color, and each plant's flowers were roughly the same size and had four petals. The petals on both variations seemed to grow with one pair of petals growing one way together, and the other pair growing the opposite way.  Because of these similarities, it would be impossible to name the different plants based off of what their flowers looked like. I believe the flowers are identical because of the 99% shared DNA. The flowers are the plants reproductive systems, so it makes sense that they are similar. 





Above are measurements of the flowers and an image that shows how the flowers grew in bunches.
If a plant breeder wanted to change the flower of a broccoli plant, they would have to change the genetic makeup of the plant. In order to do this, the breeder would have to select the traits they want to be changed, and purposely breed their plant with one that exhibits those traits. They could also try breeding it with a plant of the same species that has a mutation in the gene that impacts what the flower looks like. A more long term method of changing the flower is putting it in conditions that force it to adapt or be artificially selected. Then the flower would continue to reproduce as you want it to.

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