Week 14, Chapter 11 -- Freelance Writer Course home | Weekly schedule | Announcements | Instructor Info | Desire2Learn | MasteringBiology® | Honor Code | FAQs | HELP!

Introduction:

Artificial selection – also called selective breeding – is commonly used to select for different varieties of most every economically important organism. Want some examples?

• ornamental plants – think roses, petunias, snapdragons, lilies -- any plant bred for the look of its foliage, fruit, or flowers
• purebred dogs, cats, and horses are bred in all shapes and sizes, either for utility or for looks
• poultry, hogs, and cattle are bred for quick growth, milk production, lean meat, etc.
• fruits and vegetables are bred for juiciness, color, flavor, size, pest resistance, etc.

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.

• If an organism has a particularly unfavorable combination of traits, it probably won’t live long enough to reproduce, so it won’t have a chance to pass on those unfavorable traits. In biological terms, it will have low fitness.
• If an organism has a particularly successful combination of traits, it probably will be able to live long enough to attract mates and breed, passing on those favorable traits. The ones who leave behind the most offspring are, biologically speaking, the most “fit.”

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.

Part 1

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 a real-life 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:

• The example of artificial or natural selection must be a major component of your installment (i.e. you can’t just mention the selection in passing and then move onto something else). It must be clear from your story that you understand how artificial and/or natural selection works.
• Your installment should be between 450-550 words long.
• You must use at least one external reference (other than your textbook) in creating your installment, and include correctly cited links to all references you used.
• Please make sure that you have proofread the assignment and run a spell check before you post your assignment.

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.

Part 2

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).

• Just as you spell checked and proofread your original post, you should do the same for your responses.
• Please respond to posts with 0 responses first; once every post has at least one response, you are free to choose any post to respond to.
• When you respond, please use the name of the student you are responding to. That is, say "Hi Trudy" or "Hi Paul" so that you can get used to the names of the people in class. (You can find a list of "real" names and preferred names at D2L).
• Make sure your response is substantive, meaning that you have read and thought about the original post and that you are extending one or more of the thoughts in the original post or offering an additional perspective as you might in a good conversation. Pay special attention to the use of the key terms from the chapter. It is not enough to say simply "nice job", "I liked that", "I feel the same", "I disagree" etc. The goal is to thoughtfully add something else interesting and new related to the content of the original post. At a minimum this should be at least 50 words, and 50-100 is preferable. Check out this page for more on the topic of good and bad responses.

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.

Please note that points will be deducted as follows if you fail to meet the "mechanical" requirements of the assignment:

• 0.5 point will be subtracted if you fail to explicitly indicate what your "theme" is (that is, you fail to say something along the lines of "I am writing an episode for The Simpsons" or "I am writing an episode of The Young and the Restless");
• 0.5 point will be subtracted for every 2 spelling/grammatical errors (see http://english.acadiau.ca/grammar-quizzes.html and http://owl.english.purdue.edu/owl/resource/577/1/ for tips on correct punctuation in dialogue);
• 1 point will be subtracted if you fail to present your key terms in bold or colored type;
• 1 point will be subtracted if your post is too short
• 1 point will be subtracted if you fail to list references (if specified in the assignment); alternatively, 0.5 point will be deducted if you listed your references but they are not formatted correctly.

Contemporary Issues in Biology -- BIOL 1003 Mariëlle H. Hoefnagels, Ph.D. © 2004-2015. biology1003 at OU dot edu (at = @, dot =.) Last Updated August 5, 2014 11:02 PM