BISC 495-010, Evolution, Spring 2014

Study guide for the first exam

The first exam will be Tuesday, March 11, and will be worth 15 percent of your grade for the course. If you will be absent that day, e-mail me by the end of the day on Friday, March 7, so that we can schedule your makeup exam.

You may not use your notes during the exam. You will not need a calculator.

The exam will consist of 15 questions. Each of your answers should consist of one to a few sentences. While there is no strict length limit, you may get points off for writing long, rambling answers that say the same thing over and over.

Here are some practice questions. Try answering them, then highlight the invisible text inside the red box (drag your cursor across it) to see my answer.

1. Based on their similar size, short tails, and cute noses, you think that guinea pigs and rabbits are more closely related to each other than they are to rats and mice. How would you test this hypothesis? What result would be consistent with your hypothesis?

Answer: I would collect DNA sequence data from one or more genes in the four species. If my hypothesis were correct, I would expect the difference in the DNA sequences between guinea pigs and rabbits to be smaller than the difference between them and rats or mice.
--->[If a question asks for one answer, and you can think of more than one possible answer, just put down the one that you think is most likely to be correct. You won't get extra credit for having both correct answers if only one was asked for, and if one of your answers is right and one is wrong, you'll get graded based on the wrong answer. For example, if you wrote: "I would collect DNA sequence data from one or more genes in the four species. If my hypothesis were correct, I would expect the difference in the DNA sequences between guinea pigs and rabbits to be smaller than the difference between them and rats or mice. I would also look for rabbit-guinea pig hybrids in the Precambrian fossil record; if my hypothesis were correct, I would find them", you would get zero points, because the second half of your answer is very wrong.]

2. Rodents make the enzyme L-gulonolactone oxidase, which they use to synthesize vitamin C; primates do not make this protein, and therefore have to get vitamin C from their diet rather than synthesizing it. How would you determine whether the common ancestor of rodents and primates was able to synthesize vitamin C? Give all the possible results of your experiment and how you would interpret each one.

Answer: I would use DNA sequence data to estimate the evolutionary tree of rodents, primates, and other mammals. If the closest outgroup to rodents and primates could synthesize vitamin C, I would conclude that the common ancestor of rodents and primates could synthesize it; if the closest outgroup could not synthesize vitamin C, I would conclude that this ability evolved in the rodent lineage.

3. You've decided to write your term paper about ammonites. What are the three most important things you would do to find scientific literature about ammonites?

Answer: 1. Do a topic search for ammonites in the Web of Science.
2. Pick some of the articles from the topic search and look at their reference lists for good older papers.
3. Pick some of the best papers from steps 1 and 2 and use the Web of Science to find more recent papers that cite them.
--->[Note that if a question asks for more than one answer, be sure to give the correct number of answers. Numbering the answers, as I've done here, may help you keep track of this.]

4. You find a layer of limestone with some interesting fossils, and just above it is a layer of basalt. You use 235U/207Pb to estimate the age of the basalt, and it gives an age of 350 million years. How could you check to see whether this age estimate is correct? What might cause the age estimate based on 235U/207Pb to be incorrect?

Answer: You could estimate the age of the rock using a different set of isotopes, such as 238U/206Pb.
or
You could estimate the age of the limestone layer using index fossils; if it is much younger than the basalt layer, something is wrong.
Your 235U/207Pb estimate could be wrong if some of the lead has leached out of the rock.


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This page was last revised March 5, 2014. Its URL is http://udel.edu/~mcdonald/495studyguide1.html