A Matter of Selection

In the Willow Glen Garden we have been growing a species of plant called brassica oleracea. From the time we first planted the seed and when they first sprouted, we could not notice any real differences.  However, now that they have grown almost to adult hood there are quite a bit of differences between them.  Because we have just finished our unit of genetics I can now look at these changes in more depth and understand how they happened.  One of the largest distinctions that I have noticed was the  leaves growing on the plants themselves.  Each family of brassica oleracea has a different sized leaf and shape.

Broccoli: Leaves vary from 20 to 30 cm long and 15 to 20cm wide. With green leaves and light green stem.

Kholrabi:  Leaves vary from 30 to 40 cm long and 15 to 25cm wide. They have purple stems and dark green leaves.

Dino Kale: Leaves vary from 35 to 45 cm long and 8 to 13cm wide. The leaves are always very narrow and dark green with a light green stem.

Green Cabbage: Leaves vary from 25 to 30 cm long and 15 to 20 cm wide. The leaves are dark green with light green stems.

Siberian Kale: Leaves vary from 25 to 30 cm long and 10 to 15 cm long. With dark green leave and purple stems. The leaves are also have ruffled edges.

Purple Cabbage: Leaves very form 15 to 20 cm long and 15 to 22 cm wide. With purple leaves and stem.

The data shows that all of the plants have different sized and shaped leaves.  A dino kale has long skinny leaves, but the cabbage has short wide leaves.  The characteristic that shows that largest range is the size of the plant.  One plant like to broccoli can be up to 3 feet tall where as the cabbage can only reach about one foot.

The reason why all of these plants have such different structures is because of the fact that their genes had to change because they were always having to adapt to their new environment.  Natural variation forms when there is a natural force that is affecting the species enough to make it adapt and change.  Because of this change it is common for more than one population of the same species to form.  Our plants that we are growing are great example of this.  Because natural forces it had to adapt.  However not all of the species went through the same natural force, making different populations with different characteristics.  To adapt the plant went through a number of mutations until one of them benefited the plant.  It can also be considered descent with modification.  Each generation becomes better suited to it's environment.  Another reason why there is such a large variation is because of us.  To make harvesting or anything easier they would use a process called artificial selection.  To produce a desired outcome they would change the plants anatomy. An example of this is the case with cabbage.  Humans had genetically modified it so that the buds would grow closer together. This type of selective breeding is the reason why there are so many species of brassica oleracea. 

Out of all the plants one characteristic that seemed to stay the same was the color of either the stem or the plant's leaves. The all had darker green or light green parts.  An example of this is the broccolis or cabbages that had green stems while the others had different colored stems but green leaves. I believe the reason why the one thing that they did not change was color because it never really had a reason to change. What ever thing that was making the plants adapt, must of not have need the color to adapt as well.

In order for a scientist to get a desired trait from the plant they could use a variety of methods. One could be that they move all of the plants into an environmental biome where it would force the plants to go under numerous mutations. A more modern and scientific way is that scientist could find a desirable trait, and then imbed it into the plant.