DETAILS:

Imagine that there is a kind of animal called a “critter.” At first, there is only one species of critter. For this writing assignment, your job is to describe how that one species evolves into two separate species that have several important traits that differ from each other.

Your description must make use of the following concepts, identifying each one by NAME, EXPLAINING what each concept means, and APPLYING the concept to the story of how the one species of critter evolved into two, separate species:

• ecological niche
• genetic mutation
• reproductive isolation
• natural selection
• fitness
• genetic drift

You are not required to use the concepts in the order listed above. However, by the end of your description it should be clear how the evolution occurred, how each of these concepts was involved in the process, and how the resulting two species differ from each other as a result of this evolutionary process.

Please examine the GRADING RUBRIC (below) to see how your answer will be evaluated. Note how it requires each concept to be NAMED, each one to be fully EXPLAINED, and each one to be APPLIED to the evolution of the critter into two separate species.

ANSWER LENGTH:

There is no official minimum length. However, if your answer is less than about 350 words, I suggest that you have not written enough to answer the question thoroughly, to really show you know the concepts in question – and you probably want to shoot for more than the bare minimum if you’re trying for a high score! (I tried answering this question myself. My answer was 420 words long. It was about one and a half pages, double-spaced.)

SUPER IMPORTANT, EXTRA-SPECIAL, CRUCIAL, DON’T IGNORE THEM, TIPS and REMINDERS FOR HOW TO WRITE A GOOD PAPER:

• You’ll want to start with a single population of critters. Discuss some of the variation in traits that exists among critters. (You might even discuss how genetic mutation is the cause of those variations!)
• They can’t evolve into separate species unless the population is divided into two separate populations first. So, have reproductive isolation occur early in your paper, before they start to evolve into separate species. This will then allow the two groups of critters to each evolve in their own way, not influenced by what happens to the other group.
• Reproductive isolation does not need to take place in one, sudden moment, and usually doesn’t. It can develop slowly, over time. Once it’s complete, each group can begin to evolve on its own path.
• Once you have two separate populations, the environments that each one lives in can begin to slowly diverge from each other (different climate? different food sources? different predators? etc). This would lead to each population evolving through natural selection to adapt to a somewhat different niche: different traits would be advantageous in different niches. So, you can show you understand the connection between natural selection and the way traits evolve to be adapted to a particular niche. And remember — both populations will evolve, not just one!
• When you talk about genetic mutation, make sure to give some details about what this means in terms of things like gametes and DNA.
• Remember that “genetic drift” is not just a term for “genetic changes over time.” (Genetic changes over time is…”evolution”!) Genetic drift means that certain genes/traits become more common or less common over time due to random chance and not because they are advantageous or disadvantageous. If a trait becomes more common over time because it is a helpful trait, for example, that would be natural selection, not genetic drift. In contrast, if there’s no particular reason that the trait should become more common over time, but by chance it does anyway, that is genetic drift. (It might help you illustrate your knowledge of this concept by having one of the two populations of critters be quite small to begin with.)
• Remember that evolution of new species takes place over LONG periods of time. Don’t try to have your two species evolve in the span of a generation or a few generations. Keep in mind that for most kinds of living things, it probably takes at least hundreds of thousands of years for one species to diverge into two! Similarly, if you’re going to have the environment a population lives in change over time, and have the population evolve to adapt to it, you’ll probably want to have that environment change SLOWLY, giving the population time to adapt through evolution. If the environment changes rapidly and in extreme ways, the population is more likely to just die off and go extinct before it has enough time to evolve successful adaptations.

SUBMISSION and RETURN INSTRUCTIONS:

Your answer should be submitted as a file – .doc, .docx, or .pdf are the only acceptable formats. To submit your answer, click on the “Submit Assignment” button you see at the top of this page and then select your file.

After the assignment is graded, you can view the the results by coming back to this assignment page, where you will find a general comment to you and the scoring — to see the full scoring based on the rubric, please click on “View Rubric Evaluation.” To see more detailed feedback on your work — and please do look at this, otherwise I’m wasting many hours putting in the work of giving you feedback! — you need to click on “Submission Details” and then “View Feedback.” You can then click on the diagonal arrows to make it full screen and easier to see. You will see your paper with my inserted comments. There may be a few comments, there may be a lot. Comments — even long ones — are not necessarily good or bad. They’re just my thoughts on things that I hope are useful or interesting.

Rubric

Critter Evolution Rubric

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