Week 14, Chapter 11 -- Freelance Writer
Artificial selection – also called selective breeding – is commonly used to select for different varieties of most every economically important organism. Want some examples?
In every case, the breeder starts with a variety of organisms and breeds together those that are closest to the desired trait. Then, from the resulting variety of offspring, the breeder allows mating among only those that are closest to the desired trait. If the breeder repeats the process over many generations, the result can be an organism that is quite different than the originals.
Want evidence? Broccoli, Brussels sprouts, cauliflower, cabbage, kale, and kohlrabi all descend from a common ancestor. Broccoli and cauliflower were selected for their flowers (that’s what you eat), Brussels sprouts were selected for large buds, cabbage and kale were selected for large leaves, and kohlrabi was selected for its swollen, turnip-like stem.
For even more evidence, look at all the different breeds of dogs, from Chihuahuas to great Danes to basset hounds to shar-peis to border collies. All dogs have a common ancestor, but breeders have selected for different traits such as small size, large size, floppy ears, wrinkly face, herding ability, etc.
Natural selection is the same in some ways, but it’s also different. Like selective breeding, natural selection acts on a pre-existing diversity of organisms. But instead of a breeder deciding who gets to mate, the environment selects for or against different adaptations.
Over many generations, nearly every individual in the population will have the traits that work best in the prevailing environment, and those with the worst traits will be weeded out. (If the environment changes, however, all bets are off, and different adaptations may become more successful. This is why sexual reproduction – and all the variety it generates – is a common adaptation. Variable offspring represent a “hedge” against change).
A great example of natural selection is the development of antibiotic-resistant bacteria. Over the past half century, we have used antibiotics indiscriminately, creating an environment that strongly selects for bacteria that happen to be able to survive in the presence of the drugs. Those bacteria are the ones that reproduce. As the medical community has discovered, it doesn’t take long before most bacteria are immune to the antibiotic.
Find an example of selective breeding or natural selection that interests you (anything except dogs). Because natural selection acts on all populations, and selective breeding has influenced most economically important organisms, it shouldn’t be hard to find an example. Now imagine the following scenario:
After your Academy Award winning film on DNA fingerprinting, you've made it as a big-time filmmaker in Hollywood! In fact, you're practically Steven Spielberg. You've just come up with a great new movie idea that you think might even top your last hit! The theme for your new film: artificial (or natural) selection.
Describe in detail the plot of your new movie idea based on the specific example of artificial or natural selection that you found (for more on this, see the information on the Freelance Writer assignment in the Types of Assignments page). Cut-and-paste your completed installment and post it to the appropriate forum at D2L. Some specific criteria to consider:
Note that the instructor will grade these, using the rubric at the bottom of this page. Note that this rubric is somewhat unusual for a Freelance Writer assignment rubric, because it does not require you to use three key terms from the chapter. (I did not think that enough of the key words were relevant to the assignment.) So the point distribution is just a little bit different this time around.
View sample Freelance Writer assignment.
Respond to the Freelance Writer posts of at least two other students. (If you are the first or second person to post, you will have to check back later to complete this part of the assignment).
After you have responded to two other students, go to Desire2Learn and complete the Gradebook Declaration for this week's Freelance Writer assignment. (Your Gradebook Declaration is subject to the Honor Code.)
Here is the text of the Desire2Learn Gradebook Declaration:
(2 points) I have responded constructively to the posts of at least two other students (1 point per response; 50-100 words for each).
Grading Rubric for Week 14, Chapter 11 Freelance Writer assignment:
I will use the following rubric to grade your Freelance Writer assignments. Notice that the rubric does not heavily reward creativity; I am much more interested in looking for evidence that you understand the concepts that you have chosen to explore in your episode. In fact, you won't receive full credit for this assignment - no matter how realistic your installment - if you don't provide evidence that you really understand this week's biological concepts. In addition, although you can choose your installment and theme for this assignment, keep in mind that some themes might be offensive to other students. Be careful that your installment couldn't be construed as hostile toward people of a particular race, nationality, sexual orientation or religion.
|Found example of artificial or natural selection||You found an example of natural or artificial selection = 1 points||You did not find an example of natural or artificial selection = 0 points|
|Story development||You built your installment around a correct explanation of how artificial or natural selection works = 1 point||You mentioned artificial or natural selection, but it was not the focus = 0.5 point||You barely mention artificial or natural selection = 0 points|
|Content||Your installment focused on the chapter's content = 2 points||That chapter was part of your installment but not the main focus = 1 point||Your installment did not focus on the chapter's content = 0.5 - 0 points|
|Completeness||All content from the chapter that was necessary to complete the installment was included = 2 points||One essential concept from the chapter was missing = 1 point||More than one essential concept from the chapter was missing = 0.5 - 0 points|
|Accuracy||All content and concepts were explained correctly = 2 points||You made one mistake explaining content or concepts = 1 point||You made more than one mistake explaining content or concepts = 0.5 - 0 points|
Please note that points will be deducted as follows if you fail to meet the "mechanical" requirements of the assignment: